Hello. 1987 740 heater fuse blows and melts surrounding plastic on fuse panel as soon as I turn the fan on. Does this indicate a bad blower motor? I've read something about a resistor as well. Can I move the fuse to a vacant spot?

 

yeah, likely the motor and/or resistor is fried, or the wiring is shorted. easy to replace on a 740, pull the passenger side knee bolster, and the glovebox and its right there on the side of the 'air box' (the motor+fan is inside the airbox).... I would inspect the wiring around the resistor first.

the resistor is on the outside. always a good idea to use a new resistor when you replace the motor unless the old one looks perfect.

This is about what it looks like when you've got the glovebox and knee bolster out...



thats the resistor to the left of the screwdriver tip... the motor+fan installs from the bottom of the 'bucket' on the right.


the circuit is pretty simple, power goes to the fan speed switch, and each position of the speed switch, 1-5(?) has a wire to the resistor/motor. the highest speed 5(?) bypasses the resistor and goes straight to the motor, while 1-2-3-4 go to the taps on the resistor block, and the output of the resistor goes to the motor. other side of the motor goes to ground.


moving to a different fuse position might be tricky, the fuses are prewired on the bottom side of the fuse panel such that certain ones get power from different places. Looks like fuse 16 gets its power from 'circuit X' which is on in Run and Accessory, and off in Start, and the only other fuses on that circuit are 14 (power mirrors, cigar lighter, radio, tailgate wiper) and 15 (power seats, horn, windshield washer/wiper, headlight washer/wiper if any). the heater fan is a power pig and should be on its own dedicated fuse.

 

oh, I think that picture is the 'manual' non-AC version on some european cars, you probably have a slightly different resistor but its in just about the same place

 

Thanks! Alternator went out today. Replacing it now. I'll get back to you. Is the resistor the thing that looks like a small oven element? I got the old fan out today. It's fried. The wiring to what looks like an element is fried too. I'll get back to it after the alternator. One thing after another. Thanks again.

 

looks like early 740's use a different resistor than the later 740s, part 1307194, and it might be harder to find. looks like its no longer sold by Volvo, but here's one thats 'New Old Stock', https://www.ebay.com/itm/Genuine-Vol...4/152711269512

gotta make sure you connect those spades up in the right order. later ones had ceramic tubular resistors, and 3 plugs.

 

Finally got back to the blower motor. It's in. Checking your link now to find the resistor. Thanks for the link! I'll keep you posted.