RussB

Car: 1988 5000CSTQ

I know that the after-run coolant pump "relay" is 100% solid-state, but is it a "latching" relay? That is, once its "contacts" close, do they remain closed until the timeout period is reached, regardless of the current flow in the relay "coil"?

I watched the after-run coolant pump and radiator fan speed 1 yesterday after engine shutdown -- they turned on and off twice, rather than turning on and remaining on for 10 minutes. My guess is that the temperature sensor was on the threshold of closing and opening, and the relay's "contacts" were doing the same -- which isn't what I expected.

SteveJ_in_TX

Not sure if it is a latching relay or not - my background is electronics but the Bentley is at home.

The way I understand it is that the turbo heat soaks the entire area after shutdown. The afterrun pump kicks in and cools the immediate area until the low temp threshold is reached, then it turns off. The turbo is still emitting heat, which again soaks the area and runs the temp up, afterrun kicks on again and does its thing.

I live in Atlanta where it gets really stinkin hot, and that is normal operation for my colling system after shutdown.

Randolph

Randolph
87 5KCSTQ
93 928GTS

RussB

Now that the after-run systems are working, I'll observe their behavior over the next couple of ~hot~ south Florida weeks. Though I have a 1.5 year old maintenance-free battery in the car, I'm trickle charging it each night with a Battery Tender -- I hate the thought of the after-run gadgets draining the battery to the point that it won't start the car.

With ambient daytime air temperatures of 85 - 90 degrees, the injector cooling fan seems to run for about 5 minutes after most shutdowns; the coolant pump and rad fan speed 1 come on only rarely. Does this sound right?