740gl 1990 Fan Blower fuse

razor007 · Post by **razor007** » 15 Jan 2010, 12:55

The fuse for the fan blower on my 1990 740 wagon keeps blowing. How do I trace the short, or figur out why? Any advice would be appreciated.

Post by **billofdurham** » 15 Jan 2010, 16:12

Welcome to Matthew's Volvo Site.

It could be a faulty switch, bad wiring between the switch and the blower motor or a faulty blower motor. Does the fuse blow as soon as you switch the fan on or does it blow after time passes?

Acess to the blower motor on the 740 is easy. This is from swedishbricks:

If you have done several 240's you should be able to do a 740 blower motor with your eyes closed! Remove the under dash hush panel on the passenger side. Next remove the right side kick panel over the fuel ecu, then remove the 2 screws holding the ecu and remove the ecu. next remove the 3 screws holding the ECU bracket, and remove the bracket. Now remove the 5 screws holding the blower motor in place and remove the blower motor. Remove the ground wire from the old motor and unplug the power wire. Install new motor in reverse order. Some cutting and modification may be required depending on the style of the motor. I have done several of these, always in less than 1 Hr. [Response 2: Ney] The only important tip is to remember to disconnect the battery, because the ECU may need to be removed in order to gain access to the blower. Also remember the small black wire with self-tapping screw is ground.

The reference to the 240 is not aimed at you.

Bill.

razor007 · Post by **razor007** » 16 Jan 2010, 08:19

Thank you for the replies. Yes, the fuse blows instantly.

Post by **billofdurham** » 16 Jan 2010, 11:42

Carefully check the wiring from the switch to see if it has been chafing on anything and exposed wires which could be shorting. There is a resistor in the blower casing but I haven't heard of these causing problems on the 740.

The yellow, blue and brown wires from the heater switch go to the resistor. The black and orange/black go the the blower relay. The location of the relay is in the attached:

740 Heater blower relay.pdf: (219.77 KiB) Downloaded 342 times

In case the relay is playing up give it a good, hard flick with your finger. Sometimes this gets a dodgy relay working again.

The final check is the blower motor itself and for this you need to get it out. Check for foreign bodies in the blower case which could be stopping it. Try turning the motor by hand. If it turns, try powering it up and see what happens.

Bill.

razor007 · Post by **razor007** » 16 Jan 2010, 17:04

Thank you for the advice Bill. I will try this out.