93-97 Coolant Temperature Gauge Modification

[tiorio]

I've been waiting for a chance to do this same thing with my laptop. After mod, my truck seems to be running a lot cooler than I thought it was, the needle hasn't hit the middle of the gauge yet, although trips have been kinda short.

I'm wondering how consistent the temp readings are between gauges. I'd assume they're pretty darn consistent but what do I know? (Answer: not much apart from how to order some resistors and work a soldering iron).

[Darwood]

I'm curious to see what you read from the ECU as well. I think we might find a lot of variation on temperatures between trucks depending on cooling system health. My gauge seems to be fairly consistent with RavenTai's experiments and observations.

Todd, what kind of ambient temperatures have you been driving in?

[tiorio]

Mid 60s to mid 70s. I haven't done more than a few freeway miles, mostly LA surface street traffic. I also did a full back- forward- and sideways flush on the cooling system not 6 months (and less than 5000 miles) ago so my cooling system should be in pretty good health.

Nothing like having slighty divergent results to make one quesiton one's soldering skills!

[Darwood]

Originally Posted by tiorio

Mid 60s to mid 70s. I haven't done more than a few freeway miles, mostly LA surface street traffic. I also did a full back- forward- and sideways flush on the cooling system not 6 months (and less than 5000 miles) ago so my cooling system should be in pretty good health.

Nothing like having slighty divergent results to make one quesiton one's soldering skills!

It looks like your ambient temperatures are the same or slightly higher than mine. The more I think about it the more I'd love to see what temperatures your ECU is reading.

[RavenTai]

This is good stuff, thanks for the ECM comparison

The bottom of the red mark is suppose to be 217, I would be bummed if it did wind up being 212. I tried to be as accurate as possible in designing the test bed, I could accept a degree or two variation from the test bed to the real engine but not 5. Do you think it could make that 5 degrees in the space left? When I called bottom of red @ 217 that was the line forming bottom of the red at the center of the needle. See attached,

Also due to the height of the needle off the face of the gauge there is some parallax error, reading vary with viewing angle. Nothing can be done about this, in the test bed the camera was set to perpendicular to the face of the gauge. The other variable is gauge to gauge variation, I would hope that they are consistent being a near Wheatstone bridge it has the potential to be accurate and consistent, time and what they are exposed to could effect things also.

My main goal in this mod was for us to have an inexpensive reasonably accurate troubleshooting and monitoring tool, we may be getting to some early results here.

I am hesitant to make the mod less sensitive. If we are seeing actual problems even if they are minor, fix the problem not the symptom, 217 is 32F above thermostat opening temp, but if we are seeing consistent hits into high needle positions on many vehicles that are otherwise good then maybe I should look into it but not any time soon. Have other things that need to come first, Will have to see what happens as summer approaches.

In general my needle stays at or near the middle at highway speeds. long acceleration can get it to pop up a bit (200 or so) but not near the red mark, I ran a early version of the mod near the end of summer on a trip to FL, it was hot and never got that close to the red mark even with a more sensitive early version of the mod. Mine seams more to rise up at low speeds where airflow is less,

Could I talk you into pulling the lights and retesting? Could they be restricting flow airflow to much? Possibly combined with some other minor cooling efficiency problems?

Tiorio at the other end of the scale, have you done any non short trips at all yet? The last bit of warming up is slow, takes over 10 miles or more to finally hit the middle.

[tiorio]

I'm doing a couple hours freeway tonight. Depending on the hour when I leave I'll try to hook up the laptop for a portion of the trip and get some data from the ECU as well.

[Darwood]

Originally Posted by RavenTai

This is good stuff, thanks for the ECM comparison

My pleasure. This mod is starting to suck me in. I wish I had found the thread about it while the testing was going on.

The bottom of the red mark is suppose to be 217, I would be bummed if it did wind up being 212. I tried to be as accurate as possible in designing the test bed, I could accept a degree or two variation from the test bed to the real engine but not 5. Do you think it could make that 5 degrees in the space left? When I called bottom of red @ 217 that was the line forming bottom of the red at the center of the needle. See attached,

If that is what you meant by bottom of red then I think that yes, it should make the 5 degrees with the space left. I think 212 will be just when the top of the needle touches the red line. From my limited experience it's about 5 degrees a needle width (give or take).

Could I talk you into pulling the lights and retesting? Could they be restricting flow airflow to much? Possibly combined with some other minor cooling efficiency problems?

This is a good idea. I'll probably try it this weekend. I'm starting to think I have some cooling issues (big surprise there). My truck definitely gets hotter with higher mphs. Slow speed (35-40) driving seems to be fine with the gauge in the center.

[Mr.Bryan]

I know this might be a bit off topic, but anyone have any resistors layin around? I'd much rather give you guys 5$ for 2 little resistors, then some company who wants like 8$ to ship a gram worth of parts...

[tiorio]

Originally Posted by tiorio

I'm doing a couple hours freeway tonight. Depending on the hour when I leave I'll try to hook up the laptop for a portion of the trip and get some data from the ECU as well.

Well, I ended up hitting the road shortly before midnight, with wife and half-alseep/half-screaming 2-yr old so me plugging the laptop in was not a priority nor well-advised distraction.

Will try to get ECU temps this week and post 'em up!

[Rookie2]

Originally Posted by Mr.Bryan

I know this might be a bit off topic, but anyone have any resistors layin around? I'd much rather give you guys 5$ for 2 little resistors, then some company who wants like 8$ to ship a gram worth of parts...

Yep, I bought two extras. I'll PM you if you still want them.


Rookie2

[alia176]

Originally Posted by Mr.Bryan

I know this might be a bit off topic, but anyone have any resistors layin around? I'd much rather give you guys 5$ for 2 little resistors, then some company who wants like 8$ to ship a gram worth of parts...

Bryan,

I have two sets of extra resistors so let me know. If you're home from school any time soon, bring $5 to the house!

Later,

Ali

[RavenTai]

did some testing on the 93 gauge and to let you guys know the mod is in fact the same for the 93-94 gauges.

there was a few degrees diffrence here and there but close enough IMO, you can read the details starting arround post # 313

http://forum.ih8mud.com/80-series-tech/53142-adding-coolant-temp-gauge.html

[alia176]

Another satisfied 80 owner with this mod. Thanks Raven!!

Ali

[Rookie2]

You can add Mr. Bryan to the list too. He did both the temp guage and the auto window up mod last week in like 8 minutes.


Rookie2

[tiorio]

Originally Posted by Darwood

It looks like your ambient temperatures are the same or slightly higher than mine. The more I think about it the more I'd love to see what temperatures your ECU is reading.

Finally got around to do at least a quick test today. Hooked up the OBD-II (AutoEnginuity ScanTool) and made a 15 min or so run. Here's what I found:

Needle parallel to white line on bottom of gauge, ECU says ~150F
Needle approx. 1/3 between white line and red line on gauge, ECU says ~174-178F

My temp maxed at 181, ambient temps mid 50s, stop-and-go driving. I'm fairly close the the range indicated. There are individual sensors for the ECU and the gauge, no? I forget...

[Beowulf]

Originally Posted by tiorio

There are individual sensors for the ECU and the gauge, no? I forget...

There are 3 stock temp sensors; A/C shutoff, ECU, and dash gauge. Some of us have added a fourth.

-B-

[RavenTai]

Originally Posted by Rookie2

You can add Mr. Bryan to the list too. He did both the temp guage and the auto window up mod last week in like 8 minutes.


Rookie2

Cool is that 10 total now?

Originally Posted by tiorio

Finally got around to do at least a quick test today. Hooked up the OBD-II (AutoEnginuity ScanTool) and made a 15 min or so run. Here's what I found:

Needle parallel to white line on bottom of gauge, ECU says ~150F
Needle approx. 1/3 between white line and red line on gauge, ECU says ~174-178F

My temp maxed at 181, ambient temps mid 50s, stop-and-go driving. I'm fairly close the the range indicated. There are individual sensors for the ECU and the gauge, no? I forget...

So your gauge has been reading low since the mod correct? If you are maxing out at 181f that would fit, the gauge is suppose to center around 189 and this seams to be a pretty good center for most of us, yours seams to be running a bit cooler.

Thermosat Specs per the FSM

Valve opening temperature: 80 – 84°C (176 – 183°F)
Valve lift: 10 mm (0.39 in.) or more at 95°C (203°F)

Depends on how you look at it, it is suppose to crack open at about 179.6 I do not think that if yours was opening at 179 it would only be at 181 by the time it got to the end of the head (where the sensors are) I think your thermostat may be opening early probably not a big deal and maybe not worth futzing over, close enough and on the good side.

Have you replaced your thermostat yet? Was it OEM?

Like B said there are separate senders for the ECU and gauge, they both seam to agree that you are running cooler than most.

[tiorio]

Originally Posted by RavenTai

So your gauge has been reading low since the mod correct? If you are maxing out at 181f that would fit, the gauge is suppose to center around 189 and this seams to be a pretty good center for most of us, yours seams to be running a bit cooler.

The truck has been running this way since the mod, the gauge vs. ECU readings have also been consistent.

Originally Posted by RavenTai

Thermosat Specs per the FSM

Valve opening temperature: 80 – 84°C (176 – 183°F)
Valve lift: 10 mm (0.39 in.) or more at 95°C (203°F)

Depends on how you look at it, it is suppose to crack open at about 179.6 I do not think that if yours was opening at 179 it would only be at 181 by the time it got to the end of the head (where the sensors are) I think your thermostat may be opening early probably not a big deal and maybe not worth futzing over, close enough and on the good side.

Have you replaced your thermostat yet? Was it OEM?

I completely flushed my cooling system (back and forward, maybe sideways too) and replaced thermostat, fan clutch, couple of hoses, and filled with distilled/toyota red some 2000 miles ago, and had a quick partial drain/refill when I r&r'd the PHH a couple weeks ago.

I would not be surprised that I am running at the cool temp I am, but it does seem that my gauge position is lower by ~10F at the same actual temp as other modders. So I think the gauge is accurate, but my range is 140 (pegged cold) to prolly 234 (pegged hot) by extrapolation. Accurate enough for me, but an interesting variation nonetheless!

Either way, I'm VERY HAPPY with this mod, thanks to all who contributed!

[Sully]

Did the mod yesterday with a little help from a friend who used to do aviation electrics for the navy. It was really pretty simple. I look forward to getting my truck put back together to see the results. Thanks RT.

[jcolegrove]

did mod a month ago. runs consistently at parallel to the horizon almost all the time. no data on OBD temp or such- sorry.

[RavenTai]

Mods # 11 & 12

good deal.

mine has beeen doing the same as before, near level most times, pops up a bit with extended idle time, especially with the AC on.

[semlin]

anyone got an extra set of resisters they want to sell? my truck is finally running so I want to do the mod gauge before the end of the month when i have a long road trip.

[RavenTai]

there was a pair of resistors in the box,

have you not recieved your package?

[RavenTai]

there was a pair of resistors in the box,

have you not recieved your package?

[semlin]

no sir. when did you send it??

[semlin]

ok add me to the list. many thanks RT, I got it and was already to mod it when the penny finally dropped and i realized it was already modded

turns out I am running 2 or 3 needle widths above the middle line so I am very glad I got it now to figure out why.

incidentily, I noticed that when I turned it off then turned it back on to ign without restarting, the needle did not return to the spot it was before, nor when I restarted it right after. It seemed to drop a needle width or so. is there any memory factor on these gauges?

[Darwood]

Originally Posted by semlin

ok add me to the list. many thanks RT, I got it and was already to mod it when the penny finally dropped and i realized it was already modded

turns out I am running 2 or 3 needle widths above the middle line so I am very glad I got it now to figure out why.

incidentily, I noticed that when I turned it off then turned it back on to ign without restarting, the needle did not return to the spot it was before, nor when I restarted it right after. It seemed to drop a needle width or so. is there any memory factor on these gauges?

I think the reason the gauge doesn't go back to the same spot is due to the input voltage. Without starting the motor your voltage will be about 12.7 volts instead of 14.4 volts when running. Going by Raven's experiments and some of my calculations, the input voltage will effect how the gauge reads.

Semlin, try to get an OBDII scanner on there if you can to read what temperature the ECU thinks it is. Also how old is your radiator and is there any crud in it? I don't recall if you replaced it when you did your head gasket.

[Beowulf]

Originally Posted by Darwood

Semlin, try to get an OBDII scanner on there if you can to read what temperature the ECU thinks it is.

That will be a neat trick on his '93.

-B-