So I have been fighting with the (low coolant) alarm since I finished up my rebuild. I am running a power fc and a wiring specialties harness factory style harness. I bled the coolant system, checked the oil level and even grounded the sensors to see if that would shut off the alarm. I unplugged the dash harness connector behind the heater box and the alarm was still going off, making me think that the problem could be in the cluster not from the wiring or a bad sensor. I wouldn’t be that bad if the alarm wasn’t so irritating, guess they don’t want people ignoring it. Anyone have thoughts on what it could be other than an cluster issue (I really don’t want to risk taking it out).

 

The alarm will be on if the circuit is open / disconnected, so unplugging connectors should make it turn on (not turn off). Aside from an unplugged connector, your problem could be a break in the harness between the sensor and the cluster. Page Z-42 of the 1994 wiring diagram suggests there are at least 3 connections between the sensor and the dash, including C1-06, X-12, X-06, and C1-01. The diagram suggests the wire is part of that bundle of wires that runs near the left fender / wheel-well, which tends to get chewed up on cars with low suspension and/or wide tires.

 

Proper air bleed will take half an hour of idling or more with opening throttle to 2~3k rpm every few minutes to circulate.
You'd also want to raise the front right of the car so that water pump (where the open bottle to bleed air sits) will be higher than the throttle body line.
Unless the water level sensor/temp sensor is bad, you have some air in your system.

 

I believe the coolant sensor grounds itself through the coolant. If i am correct you can ground the connector and the buzzer will stop. if it stops then you either have air or a bad sensor.

Matt

 

I had to replace my sensor (the one for the buzzer). It was flaky after all those years, and even after bleeding etc it would give me heart attacks going off randomly. The car only had 50k miles on it at the time, and was 23 years old. New sensor solved it.

Anything electrical is suspect on these cars since they are so old.

 

Thanks everyone. I have grounded the coolant level connector and the alarm was still going off. I will try to get more air out of the system, but the coolant has been well above the sensor each time that I have check, in fact the alarm was still going off when I had the funnel attached to the filler neck full of coolant. I am hoping that it is a simple issue that I am just overlooking, but like someone previously mentioned these cars are full of aging electronics and there could be some hidden gremlins.

 

There is a black 1-wire connector behind the power steering pump that is for the coolant alarm. It basically bridges the connection between the engine and dash harness. People frequently don't hook these up when installing an engine, it's easy to overlook. That's also a good point to test from, if you ground the chassis side of that harness it should cut off the buzzer.

Also, are you certain it's the coolant alarm? There is a light on the stock temp gauge on the dash, if that light is on and the buzzer is on there's something with that system. You will also have a low *oil* level buzzer for the sensor in the oil pan, again buzzer on and light on the oil pressure gauge on the dash.

It's a VERY simple circuit. One wire that goes to ground, if the water level is up the sensor grounds through the coolant and no buzzer. If the level is down, the sensor is in air, the connection to ground is broken, and the buzzer sounds off.

Also, the buzzer doesn't go on and off immediately. Once it is grounded again it will take a little time for it to see that it's good and shut up.

Dale

 

Dale, Thank you for the advice. The light on the coolant temp gauge is on and the buzzer is going off. The coolant level is good and I have bled the system a few times, every time I check the level it’s well above the sensor. I checked the wire connected to the power steering pump and it was connected. I wasn’t aware that it would take a while for the buzzer to go off, I will ground the water level line to the chassis and see if it goes off. Super confusing, I put all new sensors in and a new wiring harness, but I guess anything can happen. Hopefully it ends up being super simple.

 

i had a similar issue with my car, there was a break somewhere between the main harness to the dash. If you take a look at the workshop wiring diagram Z-42, you will find the coolant sensor and all the connectors that single connection passes through. I had a break between X-12 and X06, and had to run a single new wire so that the signal would pass all the way to the instrument cluster. You can check by checking continuity with a multimeter.

 

worthwhile to do a coolant system pressure test to identify any leaks considering you had everything apart

 

This thread may be of some use: Low Coolant Level Sensor and Buzzer - The Last Thread