zekgb

Came down to the garage to get something out of the car this morning and heard the HVAC blower motor running at very low speed with no key in the ignition. The only thing that I could do to stop it was to disconnect the battery ground cable. I've had sporadic instances of magic blower syndrome indicating the resistors need to be replaced and the blower itself is noisy and due for a change as well but this doesn't seem related to either condition. I've searched the archives and don't see anything similar, any ideas on where to start troubleshooting?

SQLGuy

The fan(s) will run with ignition off when the coolant is too hot (switch on radiator lower passenger side), when the A/C refridgerant is too hot (can't remember where the switch is), or when the intake manifold is too hot (switch on top of manifold in 32V cars).

The manifold switch is also badly sealed and will often get water in it if you powerwash the engine. That will lead to the fan running until you open the hood, or the battery dies. You can test this scenario by disconnecting one of the wires from the switch on top of the manifold.

Oh, wait, I now see you're really talking about the blower, and not the A/C fan. I haven't heard of that running with the key out. Could be a stuck relay or bad ignition switch. How repeatable is it?

GlenL

So it's the HVAC blower and not the radiator fan?

Weird. I'd trace the electrical diagram and see what may be the problem. Instead of disconnecting the battery there will be a fuse that will do the trick. If it still runs then you've got tip #1 on something else being wrong. I'll _guess_ that you've got a stuck thermal switch in the resistor assembly (aka "magic blower").

Mrmerlin

get an IR gun and go test to see what relay is still hot,
there are two relays that run the blower I will bet its the blower or the HVAC relay, same thing happened to my 88 S4

zekgb

Swapped HVAC relay with horn relay and that solved the problem. Blower is sounding pretty bad now though, so ordering a new one from Roger.