the coolant warning light came on my 85 the other day. Coolant levels are fine, and the car is not over heating. Everything seems normal. Any ideas? TIA

 

Is that a coolant low level warning or a coolant high temperature warning assuming your model year has both like the later models do?

 

put D100 on the tank sender and the pressure sender connections,
look for leaks on the pressure sender body

 

Anyone have pics of where these are located? I have the same warning light and fluid levels are correct.

 

It’s the coolant low warning light I believe

 

The level switch is triggered by the position of the float- if this develops a leak it will sink due to loss of buoyancy. To get the switch out of the tank, the thing has to be drained, undo the three hold down bolts [the third one is a right pain], disconnect the hoses and pull the thing out.

The alternative is to pull the plug connector off the mount and call it quits but needless to say you will have no low level alarm. As I recall the switch closes at low level so normal level is open circuit but if it happens to be the other way round you simply jumper the terminals on the connector. Ironically I tested mine about a week ago and cannot remember which way round it is!

 

IIRC jumpering the low level contacts should not turn out the light,
the light turns out with a resistance reading not a continuity reading.
If the sender has got good contacts where it plugs in then replace the sender.

 

Disconnect the electric plug on top of the expansion tank. Depressurize the system, put the cap back on and go for a drive. If your light is off, it's the coolant level switch. The round floating part of the switch gets saturated with coolant over the years and loses it's ability to swim.

My old switch.

Submerged in water, floater stays at the bottom, closing the "low coolant" warning circuit.

 

Stan,

That is my understanding - the problem with these things is getting the tank out so as to get at the level switch. I use two bolts to fasten the thing down- one could probably get way with one bolt as the tank is going nowhere - it is held in place by the hoses and is soundly mounted. The other issue is whether they are even available- I seem to remember they were NLA at one stage and if they were available your bank account will be denuded by best part of $200.

I have a spare one lying around somewhere and was planning to see if by dicking around with it I could modify it such that a knackered one will in fact work. If the float is "not floating" maybe one could cast some foam or whatever to re-float the thing!

Having a viable level alarm is a nice feature to have and if one has a concours example then shell out the dosh and be done with it . If mine goes south it will stay there unless I can fix it. My focus will always be on the temperature gauge and if that thing fails my 928 would go nowhere until it is fixed- the level gauge by comparison is little more than "early warning" and a not a must have feature.

 

Gentlemen, I don't remember specifically, but I think the coolant pressure sensor is wired into that as well. Meaning if the sensor fails to read pressure, or incorrect pressure, it will cause that light to come on.
Before I took her apart, the Red Witch suffered from random 'coolant low' fault light illumination. All levels were good. My research at the time suggested this sensor. And then I took her apart...

 

And?

 

He hasn't seen a dash warning (of any kind) since.

 

And...she is in pieces, with none of the subsystems in any kind of functioning order. Except the electrics.
However, I did note some corrosion on my coolant pressure sensor when I removed it for cleaning. I have read a write up by Stan on just jumpering it and installing the Porsche bypass. Basically an 8mm piece of tube in place of the sensor.


Correct! No, wait...every so often, when I reconnect the battery to work on something, I get dash warning lights.