Heat gauge no longer working

[RasselFlassel13]

Battery light came on the other day change the battery nothing had alternator tested came back good but replaced it just in case and the light turned off.Even my mystery headlight problems fix it self(fingers crossed) but not my temp sensor just read zero no matter how long it's been running. I don't see any wire that has been unhooked anybody have any ideas

[flatcat19]

Corrosion. Remove plug from temp sensor and clean.

[datzenmike]

Hope you kept the old alternator. Unless absolutely, perfectly sure, ever trade them in, unless it was a $60 replacement in the first place. Often the stock one just needs brushes ($7).  Replacement alternators are crap. It's possible the ground or the two wire plug in was loose/dirty/oily and physically unbolting it and re-tightening it in, fixed the problem. 

 

Temp gauge...

 

The sender is located on the the intake manifold just below the front of the thermostat cover and has a Yellow/Black stripe wire to it. Pull the wire off several times to clean the contact. If that does nothing touch it to ground. No worries the sender varies a resistance to ground to move the gauge. When grounded the gauge should read FULL HOT. If it does not move the problem is not the sender but somewhere between it and the gauge itself. The wire might be broken or the gauge no good.

 

You may have to pull the dash cluster out but first look under the steering column. There are two large 10 pin connectors, a White and a Blue. Try unplugging and plugging the Blue one in. This will clean and assure the connections are good. Did this fix the problem?

 

With the Blue one connected find the Yellow/Black stripe wire and ground it. If the gauge starts working and reads HOT the wire to the sender is broken. If gauge still does not work then the gash must come out and likely the gauge needs to be replaced.

 

I hope your gas gauge is working. If the gas gauge AND the temperature gauge are not working then this is a different and easier problem to fix.

[flatcat19]

Lol. You said gash.

[datzenmike]

:w00t:

[RasselFlassel13]

I'm at work and it hailing and rain hard the wind alone would mess up the hook even more then it is tomorrow will look for sure. My gas gage does read low as in when full it show half figured it was bent in the tank. All fuses are good and have dash lights

[la_leo]

Hope you kept the old alternator. Unless absolutely, perfectly sure, ever trade them in, unless it was a $60 replacement in the first place. Often the stock one just needs brushes ($7).  Replacement alternators are crap. It's possible the ground or the two wire plug in was loose/dirty/oily and physically unbolting it and re-tightening it in, fixed the problem. 

 

Temp gauge...

 

The sender is located on the the intake manifold just below the front of the thermostat cover and has a Yellow/Black stripe wire to it. Pull the wire off several times to clean the contact. If that does nothing touch it to ground. No worries the sender varies a resistance to ground to move the gauge. When grounded the gauge should read FULL HOT. If it does not move the problem is not the sender but somewhere between it and the gauge itself. The wire might be broken or the gauge no good.

 

You may have to pull the dash cluster out but first look under the steering column. There are two large 10 pin connectors, a White and a Blue. Try unplugging and plugging the Blue one in. This will clean and assure the connections are good. Did this fix the problem?

 

With the Blue one connected find the Yellow/Black stripe wire and ground it. If the gauge starts working and reads HOT the wire to the sender is broken. If gauge still does not work then the gash must come out and likely the gauge needs to be replaced.

 

I hope your gas gauge is working. If the gas gauge AND the temperature gauge are not working then this is a different and easier problem to fix.

 

Sorry this is an old post but I have a similar problem. My temp gauge only moves a tiny bit to the middle even after the engine is warm. I can hear the thermostat opening and closing, and the heat works just fine. New T stat, hoses, flushed the cooling system. My fuel gauge works. The tach works most of the time but I have to tap it. The SENSOR light stays on, not sure why. The oil pressure light works. The battery light now stays on, but I haven't tested the voltage yet to check the alternator. How hard is it to remove the cluster? I have the bezel and the main screws off. What else holds it? I read mike's info on pulling some slack from the speedo cable. 

 

Disregard the sensor light I see Mikes instructions for the fix.

 

I want to check the temp sending unit. But If I can't access it without removing hoses it will just have to stay in the COLD lol. I JUST put all the cooling system back together. 

[Lockleaf]

SENSOR light is simply on a mileage counter. At 60k it turns on and you disconnect a wire under the dash and connect it to a different wire under there. At 120k it turns on again, you disconnect the wires under the dash and the sensor light never turns on again. That's actually how it was designed Rio function.

 

In short, you just need to disconnect a wire under the dash

[la_leo]

SENSOR light is simply on a mileage counter. At 60k it turns on and you disconnect a wire under the dash and connect it to a different wire under there. At 120k it turns on again, you disconnect the wires under the dash and the sensor light never turns on again. That's actually how it was designed Rio function.

 

In short, you just need to disconnect a wire under the dash

Got it. Read another post on it. Still curious about the battery light and temp gauge, and actually taking the cluster out. 

[datzenmike]

The SENSOR light is to remind you to service the EGR valve. This is removal and wire brushing off of any deposits.

 

You can't possibly hear the thermostat opening and closing. Must be something else. Half way up the gauge is normal operating temps. Unplug the water temp sender wide and ground it to the intake... the gauge should move to full scale HOT reading if the gauge is working. f it doesn't the gauge is at fault. Corrosion on the plug would reduce the actual reading from the sender so make sure that it is clean.

 

Pulling some slack will allow the cluster to move towards you so you can get you wife's tiny hand up in there to unscrew the speedometer cable. It tight up under the dash, no room. 

[la_leo]

The SENSOR light is to remind you to service the EGR valve. This is removal and wire brushing off of any deposits.

 

You can't possibly hear the thermostat opening and closing. Must be something else. Half way up the gauge is normal operating temps. Unplug the water temp sender wide and ground it to the intake... the gauge should move to full scale HOT reading if the gauge is working. f it doesn't the gauge is at fault. Corrosion on the plug would reduce the actual reading from the sender so make sure that it is clean.

 

Pulling some slack will allow the cluster to move towards you so you can get you wife's tiny hand up in there to unscrew the speedometer cable. It tight up under the dash, no room.

I don't literally mean I hear the thermostat opening lol. I mean I can hear the idle drop and the engine change noise when the t Stat opens. I was flushing the system like 10 ten times last night until I hit my finger on the fan blade. Appreciate the advice I'll get to work on it.

[datzenmike]

Maybe the idle up solenoid?

[la_leo]

Maybe the idle up solenoid?

could be

[datzenmike]

I know there's one for the air conditioner compressor so engine does not stall when it kicks in. Some vehicles (not sure about the late 720) have a pressure solenoid in the pressure line to raise the idle if you turn the power steering too fast or full lock.

 

Is it a Z24i with EFI? Or maybe has the electronic feedback carb? both have a separate temp sender (from the gauge) so the mixture can be adjusted as it runs.

[la_leo]

I know there's one for the air conditioner compressor so engine does not stall when it kicks in. Some vehicles (not sure about the late 720) have a pressure solenoid in the pressure line to raise the idle if you turn the power steering too fast or full lock.

 

Is it a Z24i with EFI? Or maybe has the electronic feedback carb? both have a separate temp sender (from the gauge) so the mixture can be adjusted as it runs.

it's carburetored, 85 720 ST KC 4x4. I could have mistaken the carb coming off of choke for the t Stat opening. I just remember how my 22re sounded after draining and pouring in new coolant. But that's a different animal. Either way though, the heater works great so the t Stat is working. I'll probably borrow my brothers IR thermometer Monday just to make sure it's at the right temp

[MaxChlan]

Sorry this is an old post but I have a similar problem. My temp gauge only moves a tiny bit to the middle even after the engine is warm. I can hear the thermostat opening and closing, and the heat works just fine. New T stat, hoses, flushed the cooling system. My fuel gauge works. The tach works most of the time but I have to tap it. The SENSOR light stays on, not sure why. The oil pressure light works. The battery light now stays on, but I haven't tested the voltage yet to check the alternator. How hard is it to remove the cluster? I have the bezel and the main screws off. What else holds it? I read mike's info on pulling some slack from the speedo cable. 

 

Disregard the sensor light I see Mikes instructions for the fix.

 

I want to check the temp sending unit. But If I can't access it without removing hoses it will just have to stay in the COLD lol. I JUST put all the cooling system back together. 

I had a similar issue with my temperature gauge. My issue was the temperature sender, which is kind of a pain to get to. I was able to access it by turning the wheels full lock to the right and hoping into the wheel well. To test the gauge and wiring, stick a piece of wire into the plug and ground it to the manifold; if it reads full hot, like Mike said your gauge is good. Take some contact cleaner to it and see if that fixes the problem, otherwise the replacement sender is like $10 on Ebay. I can send you a link if need be. Changing it is kind of a bitch, but with a 10 mil (I think) extension you should be able to get at it enough to be able to turn it with your hand. 

 

If you're having trouble getting the cluster out, see my thread here where I have a picture of what the speedo cable looks like (you have to push on the top and pull out, all with like three fingers, good luck, you are able to get another quarter inch of slack by pushing the cable from the engine bay into the cab). Otherwise, the bezel comes off with two screws (be very careful with the screws, because the top hole tends to be brittle and crack) and two little slidey tab thingies (See my thread again for pictures), so you kinda have to muscle it. Once the bezel is off, its four screws for the cluster, and a bunch of wires and a speedo cable to unplug out of the back. You don't have to remember where they go, because they only go in one place. It's pretty nice. While you have that shit all apart, if you have any lights that are out/dim, replace them. I just replaced mine tonight and they look nice and pretty.