Good morning , patient is a 90 300sel. The aux fans will not come on at all even at very high temp where high speed would click in. So far I have replaced fuse 1 and replaced both relays C and D. If I bridge the A/C pressure switch I get 10.5 volts a the fan connector. If I jumper the fan direct from the battery it comes right on. So I realize I must be missing a step. Voltage seems like it would be enough for the fans to come on so must be an amperage issue? Is there a resistor pack for the different speeds? Thanks in aqdvance, George
provides the current to both the Low-Speed & High-Speed Aux Fan relays, then on to the Aux Fan Motor itself.
Fuse 5 provides current to actuate those relays,
and should a related sensor provide the ground supply, the motor is then actuated.
One needs both fuses for either the Low or High-speed to function automatically.
Here's a diagram for you .. just in case.
As an aside here
, 10.5 volts is kinda low I feel. Normally, the battery should be roughly speaking 13.8-14.2v when the car is running.
My own albeit un-scientific research has shown alternator brushes to be quite worn at roughly 80,000 mile / 129,000 Km of service.
I've been driving elderly Volvos since 1970, usually starting when they've been at least 10 years old when I/we get them.