Adding coolant temp gauge?

[semlin]

ok

talked to the electronics guy again

to get a steady 12 volt input you can either use a zener diode and resister or an ic regulator. The zenor system will handle 100 milliamps or 1 watt and has a 12.5 minimum input. With lower voltage it flows through the actual voltage so you would not see any variation until current dropped well below 12 volts at which point it would not matter. To make one you need a test board, a box, a zenor diode and a resister (he guessed about 470 ohms) and a soldering iron. the little box would then have 2 inputs and outputs in line on the power and ground wires within a couple of feet of the gauge.

the ic regulator is the same kind of cost would handle 1.5 amps but has a minimum power requirement of 14 volts (2 volt differential). You can order one with a lower differential for more dough but my guy does not stock them. Otherwise same deal. solder one up using a test board and box.

The zener diode sounds like the way to go depending on the maximum current draw. I went back to the photos of your fluke meter and saw it went up to 956 vdc with the needle buried at the top of the red at 259 degrees but I am not sure what voltage scale that is?

Raventai, this guy will basically design it for me if you can provide the raw data.

total price of zener box regulator setup would be under C$10

 

[RavenTai]

well current depends on witch components are installed, what the temprature of R2 and what the source voltage is,

but assuming 110 ohm R1, shunt bypassing D1, 230 degrees R2, and 12.0v source

in the R1 + R2 leg .08219 amps without taking L1 into account
in the L2 + L3 leg .009411 amps without taking L1 into account
in L1 aproximatly .009443 amps

for an aproximate total of 101 miliamps plus whatever add ons we add later. at higher tempratures current would be higher. also the oil pressure gauge taps its power from the water tempraure gauge, no idea how much current is uses

the gauge takes power from a common suource as the rest of the cluster not a seperate line


I would hold off on this voltage issue until we actually confirm that it is wide enough to be a problem as it adds complication to the mod that may be unnessiary or may be reduced somehow (have a idea here)

 

[landtank]

I was th8inking that since the guage with only the 110ohm resistor installed is so sensitive that maybe once it is tuned in better the fluctuations will be minimized.

I'd suspect that the diode/resistor regulator could be attached to the temp guage for it's purpose only. That just might take cutting a few traces.

 

[RavenTai]

I was th8inking that since the guage with only the 110ohm resistor installed is so sensitive that maybe once it is tuned in better the fluctuations will be minimized.

That is exactly what I was thinking, if it can be minimized it may be of no concern. Adding the Zdiode replacement resistor will take down the sensitivity from L1, but the inputs to the needle from L2 &L3 would still be effected by voltage.

I'd suspect that the diode/resistor regulator could be attached to the temp guage for it's purpose only. That just might take cutting a few traces.

It would take cutting and bridging some of the traces not really an installer friendly operation.

 

[RavenTai]

I swapped gauges tonight, the test gauge went in my 80, and one note the part # at the top of the face card is one digit off between my 96 LX and the test 97 LX gauge. No other notable differences found.

Made a quick run into town and at least at on a summer night the 110 resistor seams to work rather well. The needle varies up and down quite a bit as it warms up and then stabilizes. With the AC off it varies between center and maybe .5 NW below center, with the ac on it varies from center to maybe 1 NW above center. Pulled into the drive through wile sitting in the line with the ac on and it started climbing. Seamed to stabilize around the 5/8 mark. So far lights on or off seam to have no effect.

I think it is a little to sensitive I do not need to have that much resolution. Need to widen the range some.

Something tells me that the gauge will read mostly above center on a hot day. 105 ohm might be better if they can be found

I’ll be driving to FL tomorrow so will be able get plenty of experience with it, hopefully watch for temperatures and see what I can do to catch any voltage variation. When I get back I will swap again and get started on a value for the ZD replacement resistor.

 

[e9999]

RT, can't you put in a thermocouple on the engine like I did, and get numbers to compare the gauge to while you drive around?

 

[RavenTai]

Eric do you have a link to where/how you installed the thermocouple? I would rather not modify anything in the cooling system for temporary coolant temperature readings, but if easily reversible might be handy.

Well the 110 Ω resistor missed 200°F but it wound up a good center point anyway.

As I said earlier late September Georgia evening (upper 70’s or so) gauge varied between just above and below “center” depending on AC use, referencing pictures from the test aprox. 187° to 190°

It was a hot day on the way to Florida, lower to upper 90’s AC on most of the time, rained part of the way, mostly freeway and high way some rural 2 lanes no stop and go traffic, gauge mostly read center to just above, aprox190° to 194°

Did some suburban style driving wile in FL, always hot, gauge read generally same as above. Wile stopped w/ AC sometimes spiked up maybe as high as 195°

Got held up fixing a lawn/garden tractor that I broke (1981 John Deere 212, cool machine) so wound up driving back late Friday night/early Saturday morning, it was rainy and cooled as I drove north, AC only for defog, gauge stayed between center and just below. 190° to 187°

Back in GA Saturday night we had a cool snap, was 60°F outside windy and humid, gauge stayed generally centered, I got cold wile pumping gas turned on the heat and got a surprise, with the heat on wile driving in traffic the temp would dip well below center, only climbing back up after sustained acceleration. Lowest aprox 183. This is just like the rise on a hot day with the AC on but in reverse.


to sumerize having a nice cross section of moderate tempraturs that would account for much of the year in the south east I think 110Ω is a good center point.


Got some free time this evening, want to swap the gauge again and start on the diode replacement resistor, I think I may go straight to trial and error and forget the pencil and paper for this part.


Tried on several occasions at different temperatures from full cold to center to monitor any needle movement from voltage change by turning on/off the high beams and rear defroster at the same time, none was observed.

 

[RavenTai]

Reference pictures

 

[RavenTai]

more

 

[RavenTai]

one more

 

[e9999]

Eric do you have a link to where/how you installed the thermocouple? I would rather not modify anything in the cooling system for temporary coolant temperature readings, but if easily reversible might be handy.

snip

.

I did one thread on this 2 or 3 months ago, something like "cheap temperature measurements". Not necessary to open anything. 5 mins job and you probably have the meter you need already.

 

[RavenTai]

just had a nasty thought, does a wire wound resistor create a magnetic field?

 

[jcolegrove]

from those of us breathlessly following your work and freely sucking the information you have gleaned...

so what is the answer to wire wound? and it appears we are very close to having a definitive answer?

great thread...

 

[RavenTai]

plan to find out about the wire wound thing tomorrow, want to see if the resistors make a magnetic field and if they do weather the air core motor is sensitive to it,

the air core motor has a metal case hopefully it will isolate it enough, I am building a power supply tonight. I am tired of constantly messing with a battery and battery charger trying to get the right voltage.

50ohms looks close for a diode replacement resistor at 12.7v if it still looks close enough at 14.5 will be ready to do my gauge take pictures of the process and finish the instructions.

Sorry about the focus the camera decided it liked my fluke better than the gauge

 

[RavenTai]

Ok good news the wire wound resistors make only weak magnetic fields that can somewhat move a compass (30 degrees) but cannot move the needle. A stronger magnetic field (tip of my screwdriver) can only wiggle the gauge less than 1 NW (needle width).

Also only 1 month late ( ) I have a beta mod that I am happy with ready for adventurous mudders with 95-97 trucks to try out. For 93-94 guys sorry I have made an error and it has been setback but is in the works.

For now those interesting in being early guinea pigs start by ordering these two resistors

50 Ω
Mouser P/N 71-RS2B-50
MFG P/N RS02B50R00FB12
http://www.mouser.com/index.cfm?han...uctid=275110&e_categoryid=356&e_pcodeid=71009

110 Ω
Mouser P/N 71-RS2B-110
MFG P/N RS02B110R0FB12
http://www.mouser.com/index.cfm?han...uctid=303097&e_categoryid=356&e_pcodeid=71009

if you have any bulbs out in the cluster now is the time to order replacements from Dan for those also.

I do not have calibration check resistor figured out yet.

In a perfect world any 3watt resistor of the above values should work just fine but it would be best to use the above resistors as others my have unforeseeable results

Full sweep peg to peg is 94°

Pegged hot 244°
Top of red is 227°
Bottom of red 217°
Center is approximately 189°
Cold line is 160°
Pegged cold 150°


If the early adapters have no problems then we will call it official.

Back to the garage to install the mod on the gauge in my truck.

 

[landtank]

it'll be in tommorrow and will have a 2 hour highway drive on it by Monday at 9:00 am

 

[RavenTai]

Nice

 

[landtank]

should have checked the links first, that second resistor will probably be a 2w one. I already have the 110 3w here.

 

[RavenTai]

2w for the 50 ohm resistor will be OK, it sees much less current than the 110 ohm resistor.


got mine installed gonna go for a spin.

 

[RavenTai]

you proably already know this but just in case dont froget to completely remove the zener diode and of course jumper that was installed earlier, since we now have a resistance for that spot the zener diode could cause troubles if left in parallel with the replacement resistor.