Well, the car is coming back together nicely. Two things came up today.

First, I have fitted a new radiator, hoses, and filled the overflow tank with the proper new fluid to the proper level. Still, the low coolant light stays illuminated. And this is thru all temperature ranges. It never runs hot. When the overflow is filled to the proper level does the sensor have a closed or open loop? I can see the electrical connector fitting but I wanted to ask before I bridged the two lines/wires. Or maybe just unplugging the connector will open the loop and should that make the light go off?

Second, the car was fitted with two new Interstate batteries in November 2023. The car did sit from about February 2024 until November 2004. I would put a charger on each battery about once a month. The starter (front) battery seems to take a very good charge, but the auxiliary battery (in trunk) will sometime not quite get to the fully charged point with my charger. I am getting a few electrical abnormalities like the overhead light not staying on, the instrument panel sometimes flickering, etc.

Could the auxiliary battery be causing the problems with the coolant level light? Can anyone suggest how to test the coolant level light?

Thanks

 

Not sure about the coolant level sensor but it's probably normally closed, and opens when the level is low. Should be easy to test. You won't damage anything by shorting it. That and the other issues you describe could well be corrosion in one or more of the fuse boxes. Water gets in there, particularly the front RHS where the drain holes block up and water overflows into the fuse module there.

When the rear battery goes low you'll get the 'consumers offline' message until it recharges so a low battery shouldn't be causing those faults. I'd take a look under all three fuse boxes.

 

The coolant level switch is typical German engineering. It is 'multiplexed' with the washer fluid level switch. It works something like this: low washer fluid has a 120 ohm resistance when low, low coolant has a 240 ohm resistance when low, passenger SAM has a voltage divider circuit, so these resistances are in series with another resistance and voltage level is evaluated to determine OK/low levels of each sensor. I have seen cases where a poor splice or corroded connector will add enough resistance to have a low washer fluid condition be evaluated as low coolant. An open wire will trigger both washer and coolant warnings. If you also have the low washer fluid warning, check the wiring. If it is just coolant, check/fill washer fluid and see if that clears it.

 

You are right - that is the craziest thing I can imagine. A low washer fluid triggering the dash low coolant light

 

I found the coolant light very/overly sensitive to the coolant level in the reservoir, The correct level is just above the white portion of the reservoir. I had it a hair under that level, saw maybe 1/8" of white and the light was on. Added just a bit and the light went off.

 

Super thanks for this info. That was all it was. I had to bring up the tank level to about 3/4 an inch above the line that separates the black from the translucent bottom. I had followed the instructions in the Owner's Manual but that did not do it. I find it surprising that they did not design some "sight level" indicator into/onto the tank. The way it is you are just kind of guessing the height. It is also interesting that most other cars (all that I have seen) have some variation in the level as the car heats up and/or cools.

I am now having a problem getting the heater to work. I will start a new thread on that one.

Thanks again!

 

Wow, you had to go that high - 3/4" above the line. I would expect a warning light to tell me that the coolant was dangerously low, not that it was one drop below absolutely full.