Heater fan and electric windows not working when running

Post Tue Jun 23, 2020 3:49 pm

Hi All,

I have a problem with my heater fan and electric windows which are working fine until the engine is running. Fan does not work at all with the engine running and the windows are intermitant. Do I need a new K7 rely?

Any help is much appreciated,

Thanks.

Post Tue Jun 23, 2020 6:51 pm

Windows are on K5. Heater fan is on K7, so the problem appears to be with the common control circuit for both relays.
Is your starter motor working properly?

Post Tue Jun 23, 2020 7:37 pm

Thanks for the reply Brian, yes the started motor operates as it should. I have ordered a new switch for the interior lights housed in the drivers door. If I wiggle it there is a clicking sound coming from electric window switch area.

Post Tue Jun 23, 2020 9:15 pm

pony2 wrote: ↑
Tue Jun 23, 2020 7:37 pm
Thanks for the reply Brian, yes the started motor operates as it should. I have ordered a new switch for the interior lights housed in the drivers door. If I wiggle it there is a clicking sound coming from electric window switch area.

That's normal, and has nothing to do with the heater fan. As you wriggle the rather crude door pin switch you are switching the relay behind the LH side of the glovebox, which switches the window supply between an ignition switched source and a permanent live source.
It's just occurred to me that I don't know the age of this car, and the K5, K7 control circuit is different in early cars from that in later ones.

Post Tue Jun 23, 2020 9:45 pm

325 1990 Touring - thanks for you help so far..

Door open and the windows work , shut and they stop working.

Post Tue Jun 23, 2020 10:44 pm

pony2 wrote: ↑
Tue Jun 23, 2020 9:45 pm
1990 Touring - thanks for you help so far..

Door open and the windows work , shut and they stop working.

That is what I'd expect if they weren't getting power from fuse 17 via K5.
All tourings have the later version of the wiring. K5 and K7 both have one end of their coils connected to two different ignition switched 12 volt supplies. The other end of the coils are joined together and are earthed through the windings of the starter motor, which have a very low resistance. When the starter motor is activated, 12 volts is applied to the starter motor windings, so now the coils of K5 and K7 have no voltage across them, so they switch off, but when the engine is running and power is no longer applied to the starter, the two coils are effectively earthed again, so the relays switch back on. In short, the voltage on the starter motor windings is the same when the engine is off, the ignition is on, or the engine is running - zero. It is only different (12 volts +) when the starter is operating, only, in your case, somehow you appear to have 12 volts here when the engine is running.
Have a look at the starter motor solenoid, and check that the green/black wire that goes to the 6mm stud is healthy and connected properly. If it is, disconnect it, and use a piece of wire to connect the green/black to a good body earth, then check whether the fan and windows work then.
Can you confirm that the door mirrors don't work either.

Post Thu Jun 25, 2020 9:40 am

Thanks for your help Brian. The started motor has recently been replaced. The 6mm bolt on stud connection in different on the new starter, being a push fit version, so this was swapped. I attached a new wire from the green/balck earth with a wire to the bodywork. Still the electric windows,heater fan and door mirrors did not operete when the engine was running. I have recently connected tweaters behind the door mirrors, on inspection it seems the wires may have been in contact. These were removed, everything now works with the engine running. I'm not sure how this might has an effect on the electrics but the problem seems to be solved the issues. Thanks again for your help.

Post Sun Jun 28, 2020 10:37 pm

First of all, there's no possible or plausible connection between tweeter wiring and the unloader relays. At no point does the wiring come anywhere near each other, so it can't even be explained by "disturbing a poor connection" somewhere.
It sounds like the starter motor has been replaced with the wrong type if it has different connectors. If it is the wrong motor, the ring terminal on the green black should be changed for an 8mm one, and it should be connected to the inner large stud on the motor solenoid - the one that has a solid link or flexible braid going to the actual motor.