an intermittent coolant level light that is no longer intermittent. It is now on constantly. I have forced as much coolant in there as
possible and it is still on. I am trying to figure out if it is the sensor
or wiring. I disconnected the sensor and the light stays on. I
the two wires and the light stays on. I am reading voltage on one of the
wires but nothing on the other. I thought I would read ground over there.
I am thinking that it is a simple on/off type switch which means that I should be able to jumper it to make it a complete circuit. Any clues on this??
are TWO sensors on that circuit - the level switch that you know
about, and a pressure switch that you don't know about. It is buried just
under the fender, a few inches for the tank, in the pressure line.
08:53 AM 11/12/00, Mike Harmon wrote:
>Thanks for the reply. I found the other sensor. Is there a set way to test these. I checked for a change in continuity with the the sensor unplugged and the engine on and off. I didn't see any change (read open either way). The brown wire read continuity to ground on both the level sensor and the pressure sensor but the other wire only read juice on the level sensor.
Each sensor has a blue/red wire and a brown wire. The brown wires are simple chassis grounds. The blue/red wires are joined together at terminal M11 at the Central Electrical Panel, so the blue/red wires should read the same thing at each sensor.
The later cars have a pressure switch plumbed into the hose from the top of the radiator to the coolant reservoir. It is about half way along the inner fender has a wire connector. It is tied into the coolant level sensor system and I really am not sure what it does ! They do often fail and leak so be careful how you handle it. It is part # 928 641 513 00.
I agree this is the first place to look. I found on the 85 that when I just touched the sensor it came apart in my hand. There is a copper diaphragm inside with a single contact. I assume any bit of water pressure is going to move the diaphragm. The contact could be dirty or the thing just ready to fall apart. The ease with which it disintegrated made me a little paranoid. Instead of replacing it with a new one I got a brass two sided nipple and replaced it entirely.
Dan the Pod Guy
the "service information model 84" document:
"The central warning system has a pressure switch located in the return line to the expansion tank which works in conjunction with the coolant level switch. If the coolant level of a cold engine is too low, this will switch on the coolant level warning light after a delay of approximately 20 seconds. Coolant will expand as the engine warms up and the coolant level will rise. If the engine is stopped and started again, the warning will go out. This happens even though the cold coolant level is too low. To avoid unnecessary troubleshooting, the pressure switch senses the pressure in the cooling system and sends this information to the central warning unit. Now if there had first been a warning from the coolant level switch and afterwards from the pressure switch, the central warning system will store this signal sequence and maintain the warning, even after the coolant has expanded and the coolant level switch has an opened circuit. In other words, when starting the engine again the warning lamp comes on, even if the coolant level appears correct. If the cap at the expansion tank is removed (to add coolant), pressure escapes and the pressure switch circuit opens. The central warning system, with this indication, assumes coolant has been added and turns the warning lamp out."