940 radiator fan intermittent

A friend's 940 has been overheating occasionally for quite a while now
requiring the heat to be cranked up in all sorts of weather to keep it
out of the red. He eventually tracked it down to the electric radiator
fan occasionally not starting but I haven't had a chance to diagnose it
further. What's involved in the fan control? Is there anything other
than a relay and a temperature switch? My two main suspects at the
moment are a bad relay, and a bad winding on the motor armature causing
the fan to not start if it happens to stop on the dead winding. Is there
anything else I should check?

 

Where is the fan? if it is in front of the radiator (and aircon) then it is
meant to give a boost to the cooling if air con is on and car is stationary
or slow moving in traffic. I would check the mechanical fan for correct
operation (it is temperature dependant) and possibly refresh the refrigerant
in the air con as there are pressure switches involved in switching the
electric fan.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

It's the primary fan behind the radiator, 940's never had mechanical
engine driven fans, at least not here.

 

IIRC the fan relay is a two speed type like the 850 and it sits low
where the battery can crap all over it.

Bob

 

And on Bosch FI the fan (relay) is controlled by the fuel computer,
which gets it's information from the engine temperature sensor. There's
no separate temp switch on the rad like you're used to on your 740.

940s with Regina fuel systems do have the separate temp sensor.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

I'm pretty sure it's a Regina fuel system, been a while since I was
under the hood but I'm pretty sure it's the car I'm thinking of with no AMM.