[RavenTai]

the first is from the left side in the first pic kind of lookign along its length


And the last two are from the back side between the air core motor of the water temp gauge and the oil pressure gauge movement.

So Rich what are you thinking about? Any ideas? I will have its values after testing but would still be nice to get as much info as possible before hand.

[RavenTai]

R2 I am glad you like the book, it ws a verry good value at $7 but free is even better. there is a nice group here

[Rookie2]

Originally Posted by RavenTai

still have not been able to find out what the boiling temperature of water is at my altitude but it is only ~840’ above seal level at the house so not much less than 212* F, I would think within 2-3 * F should be accurate enough for this purpose. 212 is a nice calibration point as the temperatures we are primarily interested in are in this area and is easy to accurately achieve.

Here's a link for a boiling point calculator:

http://www.biggreenegg.com/boilingPoint.htm

You've also got to input the current barometric pressure, as that has an impact also. If you've got the number for ASOS (Automated Surface Observation Service) at your closest airport, you should be able to call up and get the real time barometric pressure. If you can't get ahold of the ASOS number at you're closest Airport, let me know which one your closest to you and I'll see if I can look it up. Either that, or weather.com may do.


Rookie2

[Rich]

Originally Posted by RavenTai

...
So Rich what are you thinking about? Any ideas?...

I was just hoping to get enough info to identify the diode in order to ascertain its specifications. Any markings of the meter itself?

[RavenTai]

Thanks R2 that is a great link, standard day (29.92 hg") 840' gets 210.5* F,

Found this stream witch would be my closest airport, seams about 5 hours behind

http://weather.noaa.gov/weather/current/KCCO.html

And this one witch is only 2 hours behind (bigger airport and regional home of the FAA)

http://weather.noaa.gov/weather/current/KFFC.html

I’ll try to find that number for either of those fields

[RavenTai]

Rich I'll give the makings when I get home from work.

[Rookie2]

I pulled out an airport directory I've got here at the house, and it's got the phone numbers listed. ASOS is automated with minute by minute updates. You just call the number, and a robot spits out the info. Your tax dollars at work . Most airports got 'em... Peachtree, Fulton County, Hartsfield, Peachtree City, Newnan, Griffin. Let me know it you want to give it a try.


Rookie2

[RavenTai]

Cool

Can I have the #'s for

“Peachtree Falcon Field” FFC , “Newnan Coweta County Airport” CCO, and "Hartsfield" ATL

The first two are pretty close to me, ATL is about 35 miles away but should have the most accurate sensors.

what do you fly?

[semlin]

raventai, that's pretty impressive resolution . what kind of camera do you have?

[RavenTai]

It is a Nikon coolpix 4500 4.13MP, about 3 years old, overall a very good consumer camera (pro-sumer?) , it has strengths and weaknesses, one weakness is auto focus in low light, one of its major strengths is macro like this, I was literally bumping the lenses into the gauges back light diffuser taking some of those shots. it get even closer if it were not for the body of the gauge getting in the way.

As with anything else electronic you can get a better camera for less money now.

[RavenTai]

Here is a pic of the bottom of the gauge with all the markings, only the closer half is the water temp gauge, for the Kanji near the top see this thread

http://forum.ih8mud.com/chit-chat-section/57834-can-anyone-here-read-translate-kanji.html

It says “middle temperature stable” or basically “numb gauge”

At the top it has a #

“769916-420”

There are also two stamps in black ink, they are too smeared to fully read but they look like a mix of Kanji and numbers, possibly inspected by ________ ?

The 75 ohm resistor is drawn schematically in the copper sheet but The diode is not represented as it should be with an arrow and bar but instead a rectangle with a stripe at one end, not a way I have seen a diode drawn before.


On the back of the face card at the bottom it says

“YAZIKI METER”

And at the top

TOYOTA
TO

On the face of the card but where it would not be seen installed in the cluster there are 2 numbers

“16”

And

769135-582

[semlin]

Wow, if only we'd just removed the gauge and read the kanji on the back we could have saved a lot of posts

it may say "middle temperature stable" in order to be easily differentiated from another similar gauge which does not have that feature. I'm off to explore whether there might be a different p/n in use elsewhere in the world.

[Rookie2]

Originally Posted by RavenTai

Cool

Can I have the #'s for

“Peachtree Falcon Field” FFC , “Newnan Coweta County Airport” CCO, and "Hartsfield" ATL

The first two are pretty close to me, ATL is about 35 miles away but should have the most accurate sensors.

what do you fly?

Here ya go:

Peachtree Falcon Field ASOS# 770-487-1610
Newnan Coweta County AWOS# 770-254-1617
Hartsfield ASOS# 404-762-1121

You probably know this but just in case, barometric pressure is referred to as "Altimeter" (for altimeter setting) when you call these up.

I fly Cherokee Piper Warriors and Archers out of McGhee Tyson. Pretty simple trainer aircraft. Single 4 cylinder, 180 hp engine, fixed gear, fixed pitch propeller. I'm sure a lot less complicated than your used to working on. What aircraft do you work on again?


Rookie2

[landtank]

This is just a hunch based on working with asian designed electronics. So be kind if this is stupid, but they usually tend to design only one part that can be easily munipulated to to become several. As an example, our own driver's power door switche can easilly have auto up by adding a diode and filing the actuator. I have abosutely no electronic training just some seat of your pants trial and error, but I'd pull that resistor out of the circuit and see what happens.

[RavenTai]

Semlin, I should have posted that Kanji when I pulled my gauge out for pictures over a year ago.


R2 Thank you for the #'s, thermocouples should be here tomorrow.


We had 3 piper Cherokees at school good plane, one was in 99% shape, beautifully painted, the worst one our structures instructor took a hatchet to and we practiced repaired the damage. Yesterday I was working on a MD-11, on any day I can be on a 737, 757, 767, 777, or MD88,

I may work on them but flying is a demanding task, I got some seat time in a simulator, I can say with confidence I suck at landing planes. I bounced a 767-400 about 500' back off the runway, I don’t think the real thing bounces like that. I spent to much time trying to keep on the glide slop and forgot all the other stuff, even had to be reminded to lower the gear and flaps , I came in way too fast.

Rick, that is about how it is going to go, I know the diode will have to be removed and replaced with a resistor. the value of that resistor is unknown right now but a higher value will give a wider range of readable temperatures on the gauge, the 75 ohm resistor will also likely have to be replaced, that will adjust the center point up or down, right now it would center at ~140F

[RavenTai]

Progress report,

Back on this after my trip, (many Coho Salmon in my freezer ) I drilled up the chunk of aluminum, made provisions for feet (made form a relatively low heat conductance metal) that will raise the chunk off the bottom of the pot, this will insulate the element and allow oil to circulate under it. Goal here is to try to have the thermistor and thermocouple read the same temperatures by minimizing uneven heating in the chunk.

On top it has a spot milled for a thermistor, I did not want to try to track down a metric tap for it so instead it is milled for the two diameters of the thermistor and made a clamp to ensure good contact to the aluminum for both heat and as a ground for the thermistor. Three 1/8" holes are drilled for thermocouples at varying depths and a threaded hole for a ground connection.


Also did the boiling water calibration test for the digital thermometer,

I found out my digital thermometer looses the tenths past 199.9, so I don’t get sub degree resolution of boiling point in Fahrenheit but I do in Celsius

Boiling readings were
210F steady
98.8 C to 99.0 C.

Both thermocouples read the same thing at the same time (down to the tenths) , I think the bobbling in the C range was due to convection currents in the water,

Intellicast.com reported 29.99 and rising but that was 1.5 hours behind so no good

All three airports reported 30.23

At 30.23 and 840’ water should boil at 211.0 F / 99.4 C

I’ll call that <1 degree error and good enough for our purposes

I have two days off hope to squeeze in the rest of the test bed build (not much left) here shortly,



Sorry for the delay but could not miss this.

[semlin]

if both thermometers read the same and all 3 airports read the same, I'd suspect the medium, but it is close enough for me

btw shouldn't there be a bunsen burner in this somewhere? every experiement I ever did in high school had a bunsen burner.

[RavenTai]

Did the first cook tonight, voltage was a little low as I cannot find my battery charger, did I loan that to somebody? Source voltage was 12.29-12.32 through the entire cook. That may slightly move some of the results later but I got some interesting info none the less,

the gauge centers from about 170°F to about 230°F witch is slightly different than Dan’s 93 results, possibly the different gauge part #'s are actually electrically different?

Bottom of the red zone is ~260°F that is dam near where 50/50 coolant mix boils in a pressurized cooling system way to late.

The Zener diode drops .7v foreword bias and breaks over at about 2V reverse bias.

the 75 ohm resistor gets quite hot when reading higher temperatures (higher current than when reading lower temperatures) , the stock resistor is a 2watt, I think I will follow the Miata guy and use 5watt resistors to be safe.

Removing the zener diode but not changing the 75 ohm resistor would yield a gauge that centers somewhere around ~212°F, I would like to move this down to 200 witch means a higher value resistor.

About .6v across the sense coil gets the needle towards either extreme 0V gets the middle

Generic Wally World ATF smokes pretty good at 280°F and stinks bad when hot.

I have a spread sheet with the voltage results but no hosting right now. That is not it would be very useful to anybody else right now anyway.

[cary]

Since I don't know enough about circuit design, I was wondering a couple of things:

1) When you remove the zener diode, does that take the dead spot out of the guage? You mention it centers at boiling, that may actually work well, knowing that the line at 1/3 is 190f or so operating temp, middle is 212, and 2/3 line is 230f or so.

2) Can you explain what dropping .7v of forward bias and breaks over at 2v of reverse bias means?

3) If I am correct about #1 could you substitute the zener diode for a different value that still pads the guage slightly (i.e. from 190f-210f) but then allows it to move up?

Thanks

Cary

[Rookie2]

Originally Posted by cary

Since I don't know enough about circuit design, I was wondering a couple of things:

1) When you remove the zener diode, does that take the dead spot out of the guage? You mention it centers at boiling, that may actually work well, knowing that the line at 1/3 is 190f or so operating temp, middle is 212, and 2/3 line is 230f or so.

2) Can you explain what dropping .7v of forward bias and breaks over at 2v of reverse bias means?

3) If I am correct about #1 could you substitute the zener diode for a different value that still pads the guage slightly (i.e. from 190f-210f) but then allows it to move up?

Thanks

Cary

I'll take a shot at #2, although I only got through chapter two of the circuits book Raven hooked me up on (the library got in Nick Mason's "Inside Out: The history of Pink Floyd", so I've been side tracked the last week).

If you read through Raven's post #54, you should get a better idea of how the diode works. Initially there is a voltage difference across the diode (I presume because of the resistor). The diode allows a certain amount of voltage drop (current flow) forward bias (guage moves), then blocks current flow (guage does not move). As the voltage continues to increase on the opposite side of the diode, it exceeds the voltage on the initial side. Once this voltage difference increases above the capacity of the diode ("break over" point), current flows in the other direction... reverse bias (gauge moves again).

Am I all wet here Raven?


Rookie2

[semlin]

Raventai

Great work. Your results seem to be correct and it looks like there may be a major difference between 93/94 and 95-97 gauge flatspots. Landtank had the AC cut out on his 97 (226 degrees) with the gauge still looking normal. http://forum.ih8mud.com/showthread.p...t=a%2Fc+cutoff (post #6)

If I read you right then the gauge on a 95-97 is steady at 170 to 230 when it first moves and 260 when it first hits red?

Dan's 1993 was steady at 140 to 215/8 degrees on his truck, and was only at 223/5 at 3/4 on the gauge dial. I don't think any mod to Dan's truck including the low t-stat would impact on his gauge response. Perhaps his Isspro gauge is calibrated low or is in a location where it sees lower temps but I doubt either could explain that kind of swing.

I also notice the "dead" range is different. Dan has a 75 degree range, while you are finding a 60 degree range, so this would also support a different gauge response unless I am forgetting ohms law or something.

If all this is right then maybe that's why later models tend to blow head gaskets more often since you are in big trouble if the gauge ever moves at all .

If the gauges are different then it may be a crapshoot whether the same mod will work for both gauges but it may just be a matter of a different diode and resister on two identical parts, in which case we might be in luck.

[cruiserdan]

I have recently switched back to a stocker thermostat. My gauge reads the same in relation to the dead-spot. What I have noticed is that my Isspro must be pretty close to on because the new stat gets the motor up to 190 and won't let it drop below about 188 or so even on a log downhill coast. That is consistant with what is suppsed to be a "190 degree" thermostat. The 190 starts to open a bit below 190 which would explain why I can get it to fudge to just under that on a long coast. The 160 TRD stat would let the motor cool off to as low as 170 or so in the same situation.

As Photoman observed some time back the only thing a lower thermostat will do for you is increase the time window before you over-heat, it won't do a damn thing about over-heating.

D-

[e9999]

Originally Posted by cruiserdan

I have recently switched back to a stocker thermostat. My gauge reads the same in relation to the dead-spot. What I have noticed is that my Isspro must be pretty close to on because the new stat gets the motor up to 190 and won't let it drop below about 188 or so even on a log downhill coast. That is consistant with what is suppsed to be a "190 degree" thermostat. The 190 starts to open a bit below 190 which would explain why I can get it to fudge to just under that on a long coast. The 160 TRD stat would let the motor cool off to as low as 170 or so in the same situation.

As Photoman observed some time back the only thing a lower thermostat will do for you is increase the time window before you over-heat, it won't do a damn thing about over-heating.

D-

190 is stock? mine is lower IIRC, more like 180

add: (numbers here: http://forum.ih8mud.com/80-series-tech/53209-coolant-temperature-measurements-some-numbers.html on coolant temps)

[semlin]

a couple of other questions

-by "centred" do you mean the standard temp position that looks to be just below centre on the gauge when driving? Is this the true centre?

-if so, that means with a 75 watt resister there is 30 degrees F of swing between standard position and the beginning of red?

-am i also correct that the gauge response is linear? If so, at what temperature does the gauge first move, because I assume that 170 minus that number gives 50% of the full "range" of swing (or did you alreayd test how hot it would go before you buried the needle?)

-does that amount of swing remain fixed no matter what resister you use?

-if so, I would vote for 195 as the centre position which would yield 225 as the bottom of the red. If it is hot enough to shut down the AC that is hot enough to point at the red line. that would still leave you with what looks like 10-15 degrees of further gauge response to the top of the red. I also see no need for a replacement zenon diode to numb out any part of the temp response.

-if you can vary the swing I would suggest you decrease it a little to give a broader "red range" between overheating and the needle buried.

[semlin]

Originally Posted by e9999

190 is stock? mine is lower IIRC, more like 180

add: (numbers here: http://forum.ih8mud.com/showthread.php?t=53209 on coolant temps)

These results also confirm the 97 gauge is dead until at least 220. I think we should assume 230 is correct.

[RavenTai]

Cary

1. Yes the flat spot is caused by the Zener diode. we will be removing it and I think replacing it with a resistor, you could replace it with just a wire and have still have a linear gauge, I was originally thinking this would lead to too small of a range but running the #'s just a wire might be about right.

That would be too easy


2. R2 you got it , one addition, the forward volt drop is a thing of all diodes, in order to perform their electronic check valve function they take a tax of dropping a certain voltage, silicon and germanium diodes drop different amounts but I cant remember witch is witch. Maybe .7v is silicon?

3. I have briefly considered this but I think I want to see all changes/trends however small. It could be done though I am not sure it would be as tight as you are looking for, we already have a forward volt drop that cannot be gotten around and adds to the reverse volt drop, so even a very low value Zener Diode might have a considerable dead zone. I will try to figure that one out at least on paper

Originally Posted by semlin

Raventai

Great work. Your results seem to be correct and it looks like there may be a major difference between 93/94 and 95-97 gauge flatspots. Landtank had the AC cut out on his 97 (226 degrees) with the gauge still looking normal. http://forum.ih8mud.com/showthread.p...t=a%2Fc+cutoff (post #6)

Good to know, I was worried about the difference, but I am not going to call the results 100% accurate just yet because of the voltage.

If I read you right then the gauge on a 95-97 is steady at 170 to 230 when it first moves and 260 when it first hits red?

Yep, also 145F° was just above the cold line,

Dan's 1993 was steady at 140 to 215/8 degrees on his truck, and was only at 223/5 at 3/4 on the gauge dial. I don't think any mod to Dan's truck including the low t-stat would impact on his gauge response. Perhaps his Isspro gauge is calibrated low or is in a location where it sees lower temps but I doubt either could explain that kind of swing.

I also notice the "dead" range is different. Dan has a 75 degree range, while you are finding a 60 degree range, so this would also support a different gauge response unless I am forgetting ohms law or something.

Yep Dans readings of gauge vs gauge are still valid, only thing that is not comparable to stockers is what temperature he is running.

I am defining the dead band by watching the voltage across the windings, finding the dead band by watching the needle (waiting to actual movement instead of start of voltage change) may be enough explanation of the 15° difference in range but not the different temps the range happen at.

If all this is right then maybe that's why later models tend to blow head gaskets more often since you are in big trouble if the gauge ever moves at all .

If the gauges are different then it may be a crapshoot whether the same mod will work for both gauges but it may just be a matter of a different diode and resister on two identical parts, in which case we might be in luck.

After we get the mod someone will need to open up a 93/94 and see what is there, the thermistor is the same, if the air core motor is the same then the mod will still work. As the rest will be replaced.

[RavenTai]

Thanks for the linkls definatly want to center @ 200

[cruiserdan]

Originally Posted by e9999

190 is stock? mine is lower IIRC, more like 180

OK, here is what the book says, perhaps 190 may not be completely accurate I don't know.

The stock stat is stamped 82 (which is 179.6 F). The TRD stat is stamped 71 (which is 159.8 F). The FSM states that the opening temperature of the stock stat is 80-84 C (176-183.2 F) and that the "valve lift" is 10 mm or more at 95 C (203 F).

I wish I could find published hard numbers for the "normal" operating range of these engines. I have yet to find that. Reading between the lines you find such things as the A/C cut-out at 226 F and the cut-in at 217 F. Based on info such as that I assume that the top end of "normal" is around where the A/C will come back on.

[RavenTai]

Originally Posted by semlin

a couple of other questions

-by "centred" do you mean the standard temp position that looks to be just below centre on the gauge when driving? Is this the true centre?

It is interesting you mention this, the gauge in my 96 LX “centers” dead middle of the gauge wile driving, the test gauge appears to be maybe half a needle width low when centered, may be parallax error as the needle is pretty high off the card. But no matter center is easy to find electrically, it is when there is no current in the inductor L1 shown in the schematics in post # 58, when there is no current passing through L1 there is no volt drop across it and the needle centers. This would be whatever position you see when normally driving after warm up but before overheat.

-if so, that means with a 75 watt resister there is 30 degrees F of swing between standard position and the beginning of red?

-am i also correct that the gauge response is linear? If so, at what temperature does the gauge first move, because I assume that 170 minus that number gives 50% of the full "range" of swing (or did you alreayd test how hot it would go before you buried the needle?)

-does that amount of swing remain fixed no matter what resister you use?

Well first off after removing the diode there are two adjusts that can be made,

The 75 ohm resistor does not effect swing per say, this resistor affects the balance point or basically at what temperature the gauge “centers”.. The 75 ohm resistor and the thermistor create a variable voltage between them. These two resistors form the raw data of temperature. The rest of the circuit reads and displays this data. One thing to note, we will not lower the value of the 75 ohm resistor, only raise it. The lower the resistance of this pair the higher the current, already when reading higher temperatures the 75 ohm resistor gets quite hot, have no idea how much overhead there is for higher current in the circuit so only safe path is equal or lower current than stock. Fortunately going to a higher resistance move the center temperature lower, I don’t think anybody wants center higher than 212 so we are in luck.

Also may have found a way to tell if a truck has ever been overheated, more on that later.

The second adjustment is the resistor that replaces the diode, this adjusts how sensitive the needle is, lower resistance make for more needle swing per degree or a tighter range, higher resistance less swing per degree or a wider range.

So the gauge is completely adjustable within limits.

The variable voltage produced between the 75 ohm resistor and the thermistor is linear up to about 245°
Where it starts leveling off.

I guess eventually response would end but that point is above the boiling point of coolant so no worries. I do not know if the gauge will response will be linear or not as I was mainly watching the circuit electrically on the first cook, but for now it looks promising. It is harder to accurately measure needle movement than temperature and voltage. I think photography will help here, need to change up the test bed some.

-if so, I would vote for 195 as the centre position which would yield 225 as the bottom of the red. If it is hot enough to shut down the AC that is hot enough to point at the red line. that would still leave you with what looks like 10-15 degrees of further gauge response to the top of the red. I also see no need for a replacement zenon diode to numb out any part of the temp response.

-if you can vary the swing I would suggest you decrease it a little to give a broader "red range" between overheating and the needle buried.

195 center might be a little low. From what I can gather a system in good shape can go up to 200 on a hot day and still be considered normal, I would like all of the top half to be in the above normal range. If a lot of people see their gauge as just below center then 195 might be better.

225/226 sounds good, needle buried will still be in the pissing HG/exploding radiator range. No need to see above boiling coolant temps just loosing resolution you cannot use.

[semlin]

mine is definitely a tad below centre and that's the way I've always heard it described. It could be the combination of the angle I am looking at it when driving and the distortion caused by the raised needle from the gauge.

that raises the interesting question of whether what you see as the red line in the test is the same as it will appear in the dash. I think you may want to verify your observations from a simulated driver's eye view, although that would, if anything, mean you have so far understated the temperature at which you hit red!!

if you can vary the swing then I am ok with a 200 degree centre point. I was worried that would yield a 230 degree red line which is too high imho. If you can tweak it with enough precision to ensure 225 or so is the red line then 200 is fine.

We talked about making an overlay for the gauge card with a couple more increments. it looks like it would be impossible to remove the needle so as to accurately scan the gauge so we will need to figure out what the radius is of the circle. with that info I can try to get started on putting together the overlay. If I know what the target swing and centre point will be then I can aim for a mark at say 217 degrees for a yellow line, and 200 for a white line.

I am also going to start looking around for a 93-94 gauge.