Instrument Pod

Coolant Light Always On

I had an intermittant coolant level light that is no longer intermittant. 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 jumpered 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??

Thanks
Mike
'87 928 S4 5 spd



I looked at the wiring diagrams and it is an on / off switch operated by a float. The brown wire goes to the MP5 ground point. You should be able to jumper across the switch to test it. I don't know if open or closed is the full coolant indication.

The problem could be with the ground contact. Probably at the switch itself rather than the ground point.

Of course the problem could also be with what looks like a control unit.

Ken '86.5 928S



There 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.

Wally Plumley
928 Specialists


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.

I know I could just order both sensors and troubleshoot by swapping them out but I would rather not spend money I don't have if I don't have to.

Mike
'87 928 S4 5spd



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.

Wally Plumley
928 Specialists