1986 - 2.8 Water Temp Gauge

[AMC86Kid]

ok i have removed the dash and took the temp gauge out of the dash like so 

 

notice it has 4 connectors on the back 

 

however only 3 of them are used on the mother board 

 

now that i have it removed i should be able to completely bypass all the wires I'm unsure of and connect it straight to the temp gauge 

but I'm not sure exactly how the three prongs should be connected 

 

i have this temp sensor 

http://www.autozone.com/engine-management/temperature-switch/duralast-temperature-switch/129205_385179_15458?&searchText=tu66

i have also tested it with an ohm meter and the sensor does work

 

i have tinkered around and got the needle to move far right and far left but no luck on getting it to respond to the temp sensor properly 

does anybody know how this gauge should work?  if not i guess i will just go buy a new gauge 

[Green Mesa XJ]

Um, it's not going to play nice with another none oem gauge in that cluster.

 

Slow down a little on tearing the cluster apart. Working full instrument clusters like that form 1986 are kind of rare.

 

Look at the printed circuit on the back of the cluster, you should be able trace where the prongs that make contact go, one line will definitely go back to the main plug, you might be able to tell what color wire is feeding the signal. At least this is how I troubleshot the fuel gauge before. Though Didn't take it apart to trace it but you know for sure where it connects at.

 

Also check the printed circuit is good I have several of these clusters 84 to 86- early 87 with bad printed circuits peeling away from itself. The printed circuits were non longer stocked by jeep in 2000, local dealer had a really cool guy who was a life long jeep parts dept who was awesome about looking $#!& up.

 

I'll get my 1986 jeep electrical trouble shooting guide, it should have a way to test it but it'll be later tonight before I can get to it.

 

I do have those temperature gauges in my old clusters, I can send you one if you really need it.

 

Usually it the sensor or wire connecting to the sensor that fails.

 

 

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[Green Mesa XJ]

I forgot about fuses, there could be a fuse blown for the cluster.
The 1988 book has better trouble shooting instruction and it should be pretty much the same.
This from the 1986 electrical book



This is from the 1988 Comanche electrical book


The C307 they talk about is the wire going to the sensor. I think disconnect it for one reading then ground it for another. Remember that wire could be bad too. Sits damn close to the exhaust.

If you can't read them from the pics I could email them to you.


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[AMC86Kid]

so the gauge is current and resistive controlled 

dam that sucks i was definitely sending resistance to it but i have no clue how much current to send it 

have you ever tried to take one of your gauges and tried to wire it and see if you could get it to work outside of the dash

if you can figure out how it works then i can test mine the same way 

all i could figure out is that one terminal gets 12 volts positive and I'm not 100 percent sure on the other two pins but they must get some sort of resistance 

and which fuse should i check cause theres a lot of them 

[Jeep Driver]

In your other thread- you stated that you let the V6 run from a cold start for 3 minutes,  you stated that water did not flow. 

 

From a cold start my engine will take 7-8 minutes to get to a running temp of 195, and it stays there, Efan cycles at 195, I have a 192 stat. 

 

Your V6 running temp should be between 160 and 180, no more. You do not have an electronically controlled ign and fuel system, there is no reason to be anywhere near 210 (I don't agree with that number anyway).

If you have, for example, a 190 stat, water will not flow until 190. 

There is no way your V6 got to running temp of 190 in 3 minutes, and you came nowhere close to overheating in 3 minutes from a cold start. 

 

If you cannot afford an Infrared temp gun, you can certainly afford a $12 Sun mech temp gauge sold at every AP store. Hook that up temporarily and you should have a good idea of what your running temp is, + or - a few degrees. 

 

You are chasing your tail on this one..........and I don't know why...........

 

 

Remove the stat and see if water flows. 

[Green Mesa XJ]

I believe he replaced the thermostat and has the cooling fixed.

This would have been simpler to do a one to one swap with all the sensors. I'm not even sure that intake is off a RWD 2.8.




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[Green Mesa XJ]

Fuse box under the dash has something for instrument cluster. It should be marked.


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[AMC86Kid]

Jeep Driver  i don't remember if i stated it in my last post or not 

but i fixed the water flow problem it was the thermostat and i replaced it with a 180 

my current problem was i could not read the temp of the motor as it was running 

i hooked up an after market temp gauge,  this one :

https://www.oreillyauto.com/detail/equus-3541/agriculture-hd-parts---accessories-19818/fleet---heavy-duty-20088/instruments---gauges-20107/gauge---water-temperature-17811/water-temperature-gauge/6262/4299448/1994/pontiac/firebird

 

ran the motor for about 10 minutes and got it to go up just past 200

i need to get another cooling fan, i only have one in front of the rad i don't have one for behind it yet 

 

theres a quick update for you 

i was asking questions about this temp gauge because if i could get it to work then i will have two connected to the motor 

so if one fails and the other dosent i will know immediately 

but so far i can only get the new one to work and I'm not 100 percent sure on how acurate it is so i think I'm going to 

go and pick up a Infrared temp gun like you said 

if the temp gun says 200 degrees on the surface of the motor and the new temp gauge says 200 as well then i know 

that the new temp gauge is off because how can the inside of the motor be the same as the outside 

i should be warmer but I'm not sure by how much 

[Eagle]

15 hours ago, AMC86Kid said:

so the gauge is current and resistive controlled 

dam that sucks i was definitely sending resistance to it but i have no clue how much current to send it 

have you ever tried to take one of your gauges and tried to wire it and see if you could get it to work outside of the dash

if you can figure out how it works then i can test mine the same way 

all i could figure out is that one terminal gets 12 volts positive and I'm not 100 percent sure on the other two pins but they must get some sort of resistance 

and which fuse should i check cause theres a lot of them 

 

???

You can't "send" resistance. Resistance is a parameter of each part of a circuit. Wire has resistance. Each connector has resistance. A resistor has resistance (:duh:). A light bulb has resistance. An electric motor has resistance. You can measure resistance, with an ohmmeter, but you can't "send" resistance.

 

You also can't send current. You can send voltage. Current is draw -- the amount of current used is a function of the device that uses the power -- you don't "send" current.

 

Go back and re-read what Green Mesa posted.

[AMC86Kid]

ok i went back and read it so from what i got it has two poles that move the needle either left or right but when both are on at the same time it balances the needle in between 

the temp sensor is like a potentiometer and all it does is change the resistance to the gauge when the gauge then balances out and displays what the temp is 

however i also see that the gauge must then be current controlled because the gauge must get 12 volts (since its connected in parallel with the lights in the dash)

and the temp sender changes the resistance of that 12 volts threw the gauge which then limits the amount of current passing by one or the other poles  

 

still not sure which prong is the H-Coil and which is the C-coil 

[Eagle]

7 hours ago, AMC86Kid said:

ok i went back and read it so from what i got it has two poles that move the needle either left or right but when both are on at the same time it balances the needle in between 

the temp sensor is like a potentiometer and all it does is change the resistance to the gauge when the gauge then balances out and displays what the temp is 

however i also see that the gauge must then be current controlled because the gauge must get 12 volts (since its connected in parallel with the lights in the dash)

and the temp sender changes the resistance of that 12 volts threw the gauge which then limits the amount of current passing by one or the other poles  

 

still not sure which prong is the H-Coil and which is the C-coil 

 

You need the wiring diagram to determine which pole is 'C; and which is 'H.' Only one of them is connected to the temperature sensor. One gets a constant 12-volts, the other sees variable flow based on the resistance at the sender. The third pole at the gauge is ground, which apparently both circuits share. Since the back of the gauge has four, one of them is redundant and not used.

 

However, we can make some guesses. Look at your fourth photo -- the one of the back side of the gauge. Of the three circuit traces that lead to the temperature gauge, the upper one also connects to a terminal on the other gauge on that side of the cluster. (Is that for the tachometer, or do you have the big fuel gauge there?) The middle one connects to two light sockets, plus the other gauge. So that one HAS to be either a common 12-volt feed, or a common ground. The trace from the lower contact from your gauge doesn't touch anything else -- it runs directly to the connector header. I'm going to guess that's the C-coil. If the lower one is the C-coil, the upper must be the H-coil, and the middle one is likely the ground.

[AMC86Kid]

Eagle  

not sure if you missed it but in my third Pic

i have an small gas gauge and a large RPM gauge 

however my RPM gauge does not work (and that might be why the temp gauge dosent work either its a possibility)

my rpm gauge sits around 4,000 RPM when my engine is at idle, then when i press the gas it goes way up 

 

as of the 4th pic

yes i do see the upper on does connect to the RPM gauge (not sure how rpm gauge works havent got there yet)

yes the middle one is connected to the lights so it must be positive 12 or ground

and yes i see the bottom one goes to a direct wire 

 

i have tried to connect the gauge to a bread board and connect it to a battery and use a potentiometer to see if i can get the needle to move 

but all i can do is get the needle to move fully one way then when i reverse the polarity it full moves the other way no matter which two prongs i make 

connections with the negative terminal and one with a positive terminal i can't get it to balance anywhere in the middle of the gauge regardless of how much resistance i set it to 

[johnj92131]

43 minutes ago, AMC86Kid said:

 

i have tried to connect the gauge to a bread board and connect it to a battery and use a potentiometer to see if i can get the needle to move 

but all i can do is get the needle to move fully one way then when i reverse the polarity it full moves the other way no matter which two prongs i make 

connections with the negative terminal and one with a positive terminal i can't get it to balance anywhere in the middle of the gauge regardless of how much resistance i set it to 

 

This tells me your temp gauge is working properly.  As I understand it, you need 2 different 12 volt sources to make the needle go to the middle.  You are only testing it with one 12 volt source. So it goes to one extreme or the other extreme.Depending on which side gets the 12 volts.      You do not have a 12 volt source running thru the temp sensor to provide the other signal that would "balance out" your battery 12 volt source and move the needle to the middle.

[Eagle]

9 hours ago, AMC86Kid said:

i have tried to connect the gauge to a bread board and connect it to a battery and use a potentiometer to see if i can get the needle to move 

but all i can do is get the needle to move fully one way then when i reverse the polarity it full moves the other way no matter which two prongs i make 

connections with the negative terminal and one with a positive terminal i can't get it to balance anywhere in the middle of the gauge regardless of how much resistance i set it to 

 

Does your potentiometer have the same resistance range that the temperature sensor operates in? The section Green Mesa provided from the 1986 electrical manual gives us some numbers: 55 ohms for 260 degrees, to 1265 ohms for 100 degrees (which is "cold"). So you need a pot that gives you approximately that range. I suppose they all start at zero, but if you use one that's rated for 10,000 or 50,000 ohms on the high end, it won't take much rotation to blow right past the range for the Jeep sensor.

 

It does appear that your gauge is functioning. The second photo from Green Mesa is from the 1988 electrical manual, which is the one I have. The simple GO - NO GO test is to disconnect the wire from the sensor. This simulates infinite resistance and should peg the needle to Cold. Grounding the wire directly to the chassis (or engine) simulates low (zero) resistance, and the needle should peg to Hot. Your testing seems to have replicated that cycle, so the gauge itself is probably okay.

[Green Mesa XJ]

Other thing on these old clusters is the tarnishing on the plugs. Some clean the contacts, used to recommend an eraser to removed the tarnish. Not sure if that's still recommended.

In my experience the printed circuits on several clusters from the Deep South peeled away. Actually the original cluster suffered from a bad printed circuit too and that was bought in the high desert. But I've never had anyone I tell about this issue have it as well.
From what I've seen your circuit looked ok from what I could see of it.

Next is the power to the cluster from the fuse. Also grounds need to be ok.

Then I guess the wires in the harness, could have been nibbled on, have a broken wire some place, or where they connect to the sensor has a bad wire.

The Tachometer resting at 4k then moving up as you rev the engine sound like it's not getting power all the time or maybe a intermittent ground.
Could just be a bad tach too or for the wrong engine, but I feel like I've missed some symptoms.

Adding a full instrument cluster to a jeep with idiot lights is plug and play for the cluster, with of course changing the sensors to the appropriate ones on the engine. So it shouldn't matter if the cluster was intended for that jeep for it to work. But you're also coming after god knows how many owners and how many fixes.


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[AMC86Kid]

johnj92131

i get what you mean by having apposing poles to get it to balance out 

but what i can't do is send separate polarities to the 3 prongs

for example lets say you have prong 1 prong 2 prong 3

if 12 volts is applied from prong 1 positive to prong 2 negative it moves one way 

but if prong 2 negative and prong 3 positive are applied the same 12 volts it moves in the same direction 

the only way i can get the second connection (prong 2 and 3) to turn the other way is to switch the polarity 

but then the problem is how can prong 2 be both negative (for circuit 1) and positive (for circuit 2) at the same time

 

Eagle

i am using a 1K Pot so i can turn it and i should be able to get the needle to move almost all the way but not fully 

 

Green Mesa XJ

I'm just tying to see if i can get the original gauges to work 

if not then at least i tried and i will replace them with aftermarket ones 

i got the after market water temp gauge to work but i will get a IR thermometer and see if the data its telling me is accurate 

guess thats all i can do for now until my new electric fan shows up 

oh and do you have any idea how the RPM gauge works ?

in my 4th pic you can see it uses 3 prongs 

[AMC86Kid]

ok so i tried playing around with it again and this is what i got out of it 

 

 

 

 

i can move the needle as i turn the pot but its on the wrong side of the gauge 

 

 

[Eagle]

6 hours ago, AMC86Kid said:

johnj92131

i get what you mean by having apposing poles to get it to balance out 

but what i can't do is send separate polarities to the 3 prongs

for example lets say you have prong 1 prong 2 prong 3

 

 

The opposing coils don't have separate polarities. Both are 12-volt input. That would be one of the two terminals that also connects to other things on the circuit board. Then one of them connects directly to ground (the C-coil). The other connects to ground through the temperature sensor (the H-coil). So in your test setup, you need a 12-volt positive source to the terminal you determine to be the input. Then you connect the C-coil terminal directly to the negative terminal of your power supply, and you connect the H-coil to your potentiometer, and then connect the potentiometer to the negative terminal of your power supply. To run the test, you have to have both coils powered up at the same time, because the gauge operates by comparing the magnetic output of the two coils.

[Green Mesa XJ]

IMO the gauge works. Or had worked, dunno if testing it could do anything to it.

 

Can you get a picture of the printed circuit at the back of the cluster? If that's bad there's no point in testing the rest of the gauges, there are no replacement part for it for over 20 years. Either another 1984 to early 87 cluster or a 1988-90 cluster in its place. Aftermarket gauges would have to be bolted on to the dash or creatively adhered to the old cluster.

 

I'll post the trouble shooting for the rest of the gauges.

 

 

 

 

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[Green Mesa XJ]

From the 1988 electrical troubleshooting guide.
If you can't read some of them I can email a better picture.








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[AMC86Kid]

i did what eagle said

and i still get the same results

thought that maybe by not powering them up a the same time would change the out come but no you get the same outcome

 

oh and here is a pic of the whole back

it looks fine to me  

[Green Mesa XJ]

Printed circuit looks ok.

What happens if you do the factory Test with it in the vehicle


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[AMC86Kid]

i don't understand what it means 

i get that Tachometer inoperative means the RPM gauge 

but what does it mean by AC voltage under OK ??

[Green Mesa XJ]

Oh for the tach Test. I assumed it was looking for good old fashioned Tesla approved voltage (BTW Nikolai Tesla invented the first ignition coil) Basically you are looking for a signal from the ignition coil which cycles it up to create the spark. I’m going to stop here cause my explanation will be lacking and ignorant.

 

Did any of the gauges seem to work?

 

 

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[Green Mesa XJ]

http://www.digitalcorvettes.com/forums/#/topics/149655

Here try this thread for an explanation.




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