93-97 Coolant Temperature Gauge Modification

[80t0ylc]

Keeping track

After putting some miles on my rig with this mod it becomes very apparent how effective the temp gauge is now in monitoring how hard engine is working & cooling system health. With original gauge design, I was blissfully naive about how stable my engine temps were. I highly recommend this mod to all 80 owners with the 1FZ-FE engine. I can imagine how valuable it is for this engine with a SC setup. With the aluminum head on the cast iron block, I consider it indispensable for getting as much mileage as possible out of your HG, original or not. Just my .02 - YMMV

 

[Cruiserdrew]

Give away

I have, I think 4 extra sets of these resistors from Moser. These are the high quality ones recommended for this mod. If you would like a set to do yours (not because you're a hoarder) send me your address and I'll send you a set, at least until they are gone.

This is a great mod and the 80 should have come like this from the factory, though I understand why it didn't!


Edit:
6/28/2009 My supply is now all gone. I hope the recipeints enjoy this great mod as much as I have.

 

[maniacv]

I have one extra set if anyone needs them.

 

[malottki]

I would love a set of the resistors. Just did some hauling from tennessee and I would stare at my temp gauge hopping it wasn't getting to hot. Email me at malott_ki@hotmail.com.

Thanks.

 

[CanyonRig]

94 80 temp gauge

I was cruising down the CA-91 from Riverside to Orange in my 94 80 when the temp gauge needle went past the red zone, and remained pegged above the red zone. I exited the CA-91 as soon as possible and pulled over to safe spot and inspected. Everything seems to be intact, with no signs of leakage or smoke. The expansion tank was empty (as I filled it up 2600 miles ago from IL-CA XC trip), but the radiator was full. I was able to get home, refilled the expansion tank , and waited until the following morning to test run the engine from dead cold. The temp gauge needle is still pegged above the red zone, and when the ignition is off the needle points all the way down still.

Will this temp gauge mod fix the problem or do I need to get a new gauge assembly all together? Any other advice would be appreciated. Thanks...

 

[vkfzj80]

did the temp gauge mod today, went for a quick drive 10-15 min and the needle was about centered, we'll see how things look on the longer drives,

thanks to those that have put this mod together and created very easy to follow docs.

 

[RavenTai]

I was cruising down the CA-91 from Riverside to Orange in my 94 80 when the temp gauge needle went past the red zone, and remained pegged above the red zone. I exited the CA-91 as soon as possible and pulled over to safe spot and inspected. Everything seems to be intact, with no signs of leakage or smoke. The expansion tank was empty (as I filled it up 2600 miles ago from IL-CA XC trip), but the radiator was full. I was able to get home, refilled the expansion tank , and waited until the following morning to test run the engine from dead cold. The temp gauge needle is still pegged above the red zone, and when the ignition is off the needle points all the way down still.

Will this temp gauge mod fix the problem or do I need to get a new gauge assembly all together? Any other advice would be appreciated. Thanks...

sorry for the delay, I have been out of town

It is possible that the mod could fix your gauge if for instance if one of the two components we replace with the mod has a broken lead, but it is more likely that you have a short to ground in the wire leading from the sensor to the gauge or a short in the sensor itself, I believe that wire is in the bundle that runs near the EGR pipe, that bundle often has issues due to excessive heat,


I would pull the cluster and check the resistance of the circuit to ground at the cluster plug, see the development thread (link in first post of this thread) for charts showing expected resistance vs temperature. you could also do the mod to the gauge while it is out.

 

[thespruce]

Hi all - I have an 86 4runner, with a 2lII-T diesel swapped in. Does anyone know offhand if this mod will work with my gauge? The temp sender unit is wired into the stock gauge of the 4Runner, which was originally a gasser engine - without me pulling the dash apart to compare to the pictures, I don't know if this mod will work or not. Any help appreciated

Spruce

 

[Beowulf]

Spruce,
This mod was designed specifically for the temp gauge in the FZJ80 by reverse engineering the stock resistor values, the factory designed "dead" spot, and the desired new temp ranges. It is very unlikely that this mod will work for anything other than these specific gauges.

However, you can use the same process that Raven used to reverse engineer your gauge and come up with a similar mod.

-B-

 

[RavenTai]

I should post this here also

RavenTai,

I have an 86 4Runner with a 2LII-T swapped in. These engines are notorious for cracking heads, due largely to a slightly underpowered cooling system, and the known dead zone in the temp gauge. My 4Runner was originally a gasser, and has the original gauge cluster. Hopefully in tomorrow or in the not too distant future I'll pull my gauge out and see if it looks like yours - I know it's similar, but might not be identical. If it's not, are you able to give me the rundown on how to determine which resistors need to be added in? It would definitely be great to get that gauge working properly, Thanks

Thespruce

The first step is to see if the circuit is the same as the 80's gauge, see post #58 for a schematic,

https://forum.ih8mud.com/80-series-te...emp-gauge.html

Read that thread for the blow by blow on how we came up with the mod. long read but worth the time if you want to recreate it,

The circuit in an 80 gauge is a modified Wheatstone bridge, they used windings of the motors (inductors) in place of some of the resistors, changing the value of R1 moves the null temperature (center point of the needle) changing the value of R2 (replaces the zener) affects the range,

You will need to trace out the circuit in your 4-runners gauge to see if it matches the 80 series circuit.


Note, I would not use a R1 resistor of lower resistance than stock, circuit current is surprisingly high for PCB mounted components, dash melt down or fire could be the result if either the resistors wattage or resistance is too low.

are you using the 4 runner sender or the one from the new motor? it may not work with the later.

 

[redcard]

Anyone have a spare set of resistors?

Hello,

Interested in buying a set of resistors from someone with extra.

PM me or email at marfil_d@yahoo.com.

regards,
Mar

 

[TJ96TLC]

Completed Mod over Christmas. Thanks to all for the good advice! This pic is on a 2 hour drive to Alabama, outside temp 42deg.

 

[CycloSteve]

Great mod!

Well documented, and grateful to RT and those who worked out all of the nitty gritty. The removal of cluster took more time than the actual de- and re-solder.

Looking forward to a useful gauge now.

Cheers, Steve

 

[RavenTai]

96 TLC, my gauge shows similarly (ever so slightly low) in cool weather, especially with the heat on, looks good.

Steve glad you like, the mod fixes a fault in an otherwise well thought out vehicle,

 

[chipboy]

Do you still have them?

Interested as it is a lot harder to order over the net from Australia.

Thanks,
Matt

I have one extra set if anyone needs them.

 

[sandcruiser]

ok. Finally trying this out! Only 2 years later.... sheesh.

here are some prelim pics of the gauge "before". Note that the oil px gauge is melted and something is broken as the post that connects to the needle is not connected to anything at all.
If anyone has pics of how a functional gauge looks, I'd like t see them. I'm going to fiddle with it a little to see if it can be made to at least sorta work. Ok, pics (click for larger):






This is a gauge from an hd-t cluster. The motor is 1993. The cluster is of unknown year. But definitely from an hd-t as it has the 2 turbo lights and no gear indicators (ie: from MT). I think it is a 93-95 cluster as the newer hd-t clusters have only 1 turbo light for overboost, not the nifty green light for "you're now boosting!"

 

[RavenTai]

that gauge has seen better days.

post # 119 of this thread has a good pic of the oil pressure area,

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

There are pictures of the gauge throughout that thread. including a side by side of the 93/94 and 95-97 showing the differences with part numbers.

the charring of the PCB near the R1 resistor shows it got very hot, that could be an indication of an engine overheat, as the sender gets hotter wattage disipated by resistor r1 increases, sharply so at high engine temperatures, another possibility is that the gauge is not right for the trucks wiring or engine, that could explain the oil pressure gauge melt down.

 

[sandcruiser]

....and after pictures

Before I cut the legs off


all finished

Waiting to re-assemble on the off chance that someone can show me pics of an intact oil px gauge. I'd like to see how it is supposed to look so I can try to repair it, if possible.

 

[sandcruiser]

Thanks RT!

There is no telling if the gauge cluster and engine came from the same donor vehicle or not... so anything is possible

I'll snap another photo, but the gauge 'arm' on the px is actually bent into about 100* angle. Must have had something go very wrong!

I'm assuming that the arm connects to the spindle somehow. Might just try to glue it in there and see what happens next. Cant really hurt it more than it is already hurt right now!

i

 

[sandcruiser]

here's another shot of my pretzeled armature:

will try bending it to see what can be done.
I'd say that whatever happened to it, that is what caused charring/scarring on the gauges. It is pretty well fubar.