93-97 Coolant Temperature Gauge Modification (9 Viewers)

[7P's]

I was guessing a poor solder joint as well but when I soldered everything they looked damn good. Just went back in and took everything out - took 10 minutes this time. Everything looks good. I've got an old craftsman meter but I think it grew legs, as I couldn't find it earlier this afternoon. I'll resoldered everything again and see what happens. I got an extra pair of resistors so if this doesn't do it I'll throw the other set in tomorrow.

 

[7P's]

I resoldered using a lot of flux - slapped her in and the needle jumped right up to 2/5 at startup (engine is still hot) so I think it'll work.

 

[Rich]

Raven,

You posted the data below in a previous thread. These are tested temps for the unmodified factory gauges?

                     93   97  

Pegged hot           269  269  
Top of red           253  259
Bottom of red        242  248

Did you by chance test or calculate resistor combinations that would put needle at bottom of red zone with temperature being around 240° F?

 

[RavenTai]

Raven,

You posted the data below in a previous thread. These are tested temps for the unmodified factory gauges?

                     93   97  

Pegged hot           269  269  
Top of red           253  259
Bottom of red        242  248

Did you by chance test or calculate resistor combinations that would put needle at bottom of red zone with temperature being around 240° F?

those are for unmodified,

I did not calculate but I can, question is how accurate they would be without comparing them on a known good gauge, there is slight variation between what the thermistor curve said it should do and what it actually did but for something like this just need to get in the ball park, there is also some slight variation depending on weather it is running or not (12.x vs 14.x volt source)

34.4 ohms should get you to top of red on a modified gauge
44.5 ohms bottom of red
75 ohms just below center

240F would be 30 ohms for either gauge,

 

[Rich]

Raven, I may not have been clear on my second question. Are you able to suggest what pair of resistors I could use to modify my '97 gauge to remove the dead zone and have needle at the bottom of the read zone at approx 240°F? Thanks.

 

[landtank]

Raven, I may not have been clear on my second question. Are you able to suggest what pair of resistors I could use to modify my '97 gauge to remove the dead zone and have needle at the bottom of the read zone at approx 240°F? Thanks.

So you're thinking that anything under 240* is realistic?

I personally like it very much where it is right now.

I look at the AC cutoff mark as the "Oh s*** we've got an issue here" mark and lets start taking systems off line before it hits the fan.

 

[RavenTai]

ahh I though you were asking about calibration check resistors.

To answer no, not with any accuracy, what the gauge did on paper was always noticeably off from testing.

At the end of the development thread Darwood did some calculations with some resistors, calculating for anything outside of the center (balanced Wheatstone bridge) requires working with thevenin equivalents something I could not master without sinking a lot of time in it. Darwood apparently did work it out, I have not had a chance to test any of his suggestions

you would want to raise the value of the diode replacement resistor to widen the range, changing resistor R1 changes the center point, changes in one have a slight effect on the other, I have not been able to figure it out on paper alone, trial and error was required but you may have better luck.

Personally I would have no use for a 240F red but that is your truck

 

[Rich]

So you're thinking that anything under 240* is realistic?...

I would like the needle hitting the red zone to indicate the need to stop immediately and let the engine cool down.

It all depends on the context, in general, if the engine were running at say a steady 220° F, in a situation where running hot is to be expected, I.E. heavy loads, steep mountains in the summer desert, then I think that is acceptable. A spike to 230° F near the top of a steep pass wouldn't likely cause me to stop.

In contrast, seeing 220° F on a cool fall evening driving the flats lightly loaded would merit serious attention, and that's why I mention context matters.

I'd like have the gauge setup such that having the needle near the red should be concerning and having the needle in the red should demand action, and for me, 216° F seems too low to demand stopping the vehicle when operating with high loads in very hot ambient conditions.

In general, I think that the red zone should be used to indicate that the danger of boil over is being approached, and having 240° F at the beginning of the red leaves a large margin of over 20° for that.

 

[RCFloyd]

Ye-haaw! Done. Works like a champ, in-that, it moves! I haven't put it to any test yet, but I'm sure that it's A-OK.

Also replace my new 180 degree Stant T-stat, with OEM 195 degree. I feel that it's important to maintain the 'hot' side of things; the way that the factory intended...

Schucks, and I do mean shucks... I order my Hayden Fan Clutch from them for $65, but when it wasn't there when it was supposed to be, had a friend swing by to pick the pre-paid unit up for me. But, wait, they wouldn't give it to him, even though I'd called ahead and given his name... they needed the credit card that had already been nicked for the part! He offered cash, CC, his first born... all to no avail. Not very nice considering that it is a 130 mile round trip for me. Weird world, eh? Order stuff all day long w/o a physical card, and then this...

Thanks to all who helped in this venture

Robert

 

[landtank]

Also replace my new 180 degree Stant T-stat, with OEM 195 degree. I feel that it's important to maintain the 'hot' side of things; the way that the factory intended...

My OEM thermistat was stamped 82*C, that's 179.6*F.

 

[Darwood]

I would like the needle hitting the red zone to indicate the need to stop immediately and let the engine cool down.

It all depends on the context, in general, if the engine were running at say a steady 220° F, in a situation where running hot is to be expected, I.E. heavy loads, steep mountains in the summer desert, then I think that is acceptable. A spike to 230° F near the top of a steep pass wouldn't likely cause me to stop.

In contrast, seeing 220° F on a cool fall evening driving the flats lightly loaded would merit serious attention, and that's why I mention context matters.

I'd like have the gauge setup such that having the needle near the red should be concerning and having the needle in the red should demand action, and for me, 216° F seems too low to demand stopping the vehicle when operating with high loads in very hot ambient conditions.

In general, I think that the red zone should be used to indicate that the danger of boil over is being approached, and having 240° F at the beginning of the red leaves a large margin of over 20° for that.

Hi Rich I fully agree with you. I finally posted an equation up in the development thread. I'll post some more info later.

https://forum.ih8mud.com/showthread.php?p=1251128#post1251128

I really think you might like the 150 ohm RD1 and 100 ohm R1 replacements. With this setup the needle should look like this at 238 degrees F:

 

[RCFloyd]

Dang, gang...

I just did the math for the conversion too...
82C does equal 179.6!! Now where did we get the idea that the OEM T-stat was 195?

Oh well, the OEM does seems to be more HD...

On another note, Darwood's new calculations with the accompanying suggestions for different resistors is about a week late! I really would have liked to go with these other units too, because is just seems that the original modification was a little to 'loose' in what the interpetation could be.

Could we have some part #'s please for the newest rendition?

Thanks,

Robert

 

[Rich]

Thanks Derek. Looks like that should do the trick. Thanks also to Raven for doing the great ground work.

 

[Darwood]

Looks like I need to post some more info. 180 ohms for the diode replacement is another option. With this resistor 238 degree F should look something like the attached. Right now I have the 100 ohm and 150 ohm resistors in my truck. I like it so far. When it got up to 221 the needle was about 2 needle widths below the red line and 218 was at about the 34 mark. 200 degrees is centered and 194 is just below center where the stock gauge would never move from once warmed up.

I'd also like to point out that the temp to needle values (except for my limited real world experience) are all calculated off or Raven's data and might vary slightly from their real world performance due to some assumptions I have to make when calculating. For the most part what I've expected and what I've seen have been pretty consistent when I've tested out the modified gauge vs the OBD II scanner.

 

[Darwood]

Oh yeah I should also mention that without Raven's help none of my tinkering would have been possible. He discovered what the circuit was and provided me with invaluable data. I'd also like to point out once again that any values I suggest are still experimental and I only put them out there for those who understand the risks.

In my truck I'm actually on my 3rd modification to my gauge.

 

[extremetoy1]

91 gauge yet?

has anyone sent in a 91 gauge or pics yet? i am patiently waiting!!

 

[tarbe]

Right now I have the 100 ohm and 150 ohm resistors in my truck. I like it so far. When it got up to 221 the needle was about 2 needle widths below the red line and 218 was at about the 34 mark. 200 degrees is centered and 194 is just below center where the stock gauge would never move from once warmed up.

I like the sound of that set-up. Any part #s or links for electards??

 

[Darwood]

I like the sound of that set-up. Any part #s or links for electards??

The 100 ohm resistor replaces the 75 ohm resistor and the 150 ohm resistor replaces the diode. These are the same type and brand that Raven sourced.

Mouser Part #: 71-RS2B-100
Manufacturer Part #: RS02B100R0FB12
Manufacturer: Vishay/Dale
Description: 3watts 100ohms 1%


Mouser Part #: 71-RS2B-150
Manufacturer Part #: RS02B150R0FB12
Manufacturer: Vishay/Dale
Description: 3watts 150ohms 1%


Here is the 180 ohm reisistor is anyone feels so inclined to use that. Note however that I haven't tried out this value.

Mouser Part #: 71-RS2B-180
Manufacturer Part #: RS02B180R0FB12
Manufacturer: Vishay/Dale
Description: 3watts 180ohms 1%


(I'm having issues with posting functioning links)

 

[tarbe]

Cool - thanks Derek!

I'll use the link on the first page and hopefully navigate my way to the two correct animals.

 

[tarbe]

I just ordered 5 each of the 100 and 150 ohm. I have two extra pairs available.

Anyone in the greater Houston area...you can pick up a pair...for free...first come first served...at the next monthly meeting of the TLCC-H at Matagorda Beach. See the TLCC-H link in the club section.

Buck and Ross...I have a pair for each of you if you want them!