1994 Park Avenue Low Coolant Light

I posted this problem in a Buick forum last fall, but never got a satisfactory answer ... so I'm gonna try here! I'm getting the car ready to sell, but I hate to try and convince a prospective buyer to
just ignore the warning light!
I have a 1994 PA Ultra with 135K miles on it ... and for the last 5+ years, my "Low Coolant" light on the dash has come on about 15 secs after starting the car, and stays on steady until I turn the ignition off. Coolant level is fine. Low coolant sensor in the radiator was replaced, with no improvement.
According to the troubleshooing chart in the service manual:
"If CHECK OIL LEVEL indicator is lit continuously when oil level is OK, or COOLANT LOW indicator is lit continuously when coolant level is OK, check indicator lead for a short to ground. If wire OK, replace oil level module."
Then the chart goes on in great detail about checking various connectors for various ohms or voltages, ETC, ETC, ETC !!!!
According to the wiring diagram in the manual, there are 3 wires attached to the "Low Coolant" sensor ... Brown (to a signal input on "Oil Level Module"), Light Green (also to a signal input on "Oil Level Module"), and Red/White (to power on "Oil Level Module").
Two questions:
How do I "check indicator lead for a short to ground"? Just a continuity check for all three leads to ground? Continuity on any of the leads = "short to ground"?
Does anybody know where the "Oil Level Module" is located?
Has anyone else experienced this same problem? Any directions or advice would be appreciated!
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Bankerjohn wrote:

Is your sensor in the radiator or in the overflow tank?
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The "Low Coolant Sensor" plugs into the passenger side of the radiator above the lower radiator hose.
There is no problem with the sensor ... I had it replaced at a GM dealership long after the lamp started coming on. I told them that it wasn't bad, but they replaced it anyway. I'm resonably sure it's not the sensor because the troubleshooting chart says that unplugging the wiring harness from the sensor should make the warning lamp go out ... mine doesn't!
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I don't believe you mentioned earlier that the light does not go out when you unplug the connector. No shortcuts to this fix. Get out your ohmmeter and start eating ohms.
--

-Mike-
snipped-for-privacy@alltel.net
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Mike Marlow wrote:

Agreed.
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So ... back to my orginal two questions:
How do I "check indicator lead for a short to ground"? Just a continuity check for all three leads to ground? Continuity on any of the leads = "short to ground"?
Does anybody know where the "Oil Level Module" is located?
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Bankerjohn wrote:

I don't think I can be of further help to you. Sorry. I do not know of an oil lev mod in a 94 Buick and can't tell you which wires are for what with out a schematic.
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John,
Let's go back to the top. You've unplugged the coolant level sensor at the radiator and the "Low Coolant" light is still on, correct?
Question: is the oil level indicator operating correctly?
First test is to unplug the oil level module and see if the lamp is out. If it is (and I'd almost bet it will be) and, from the symptoms you describe, I'm inclined to think the oil level module itself is defective. If you had a wiring short from the module to the indicator light it would be lit as soon as you turn on the ignition (the coolant indicator lamp is conteolled by the yellow/black wire on Terminal #4 of the oil level module)..
The location of the Oil Level Module - mounted to the bracket of the Relay Center, which is to the right of the glove box behind the IP. It is the module with 10-pin flat black connector plugged into it.
If you are going to be checking around back there, be careful of ANY wiring that has yellow connectors and/or yellow sleeving on it - that is wiring for the air bag. DO NOT disturb any of those wires.connectors!!
Do those tests and get back to us.
Regards, Bill Bowen Sacramento, CA
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William H. Bowen wrote:

Bill ... thanks for the educated reply!
Yikes ... I released the two rubber tabs that keep the glovebox from falling down when you open it ... to reveal a vast number of wires and "modules" behind the dash! With flashlight and reading glasses in hand, I looked for the relay center (which I believe I correctly identified against the right-hand side) ... but I didn't see anything with a "10-pin flat black connector plugged into it"!
Am I going to need to remove the lower portion of the dashboard to get to the module ... or am I just blind?
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John,
The oil level module is not plugged into the relay center: it is mounted to the bracket that holds the relay center. You may have to drop that lower dashboard panel to get to it.
Bill
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