blower motor issue

[MacGyver72]

I keep blowing fuses for the blower motor. I mean as soon as I put one in. I've changed the relay which fixed it for a while and then it did it again so I changed the relay to a USA one and now every fuse is blowing. This is a 20amp circuit right? Why would it keep blowing fuses?

[SS Tim]

You could have a blower motor that is shorting and drawing too much amperage. What do you have a standard heater or A/C? What fuse is blowing? What relay did you replace? Do you have a wiring diagram and or a service manual?

[MacGyver72]

I have A/C although the compressor, drier and some lines are removed. The fuse is the left most lower on the fuse panel and shows on the diagram as the blower motor fuse. The relay is located behind the glove box mounted to the air box. I initially thought it was a ground problem on the relay and with the new relay made sure I made a better ground. I haven't checked the blower motor itself and you could be correct about it shorting out. I don't have a wiring diagram so i thought I'd ask you good people to see if anyone has had this and could help.

[SS Tim]

The '70 service manual I have has schematics in both the electrical and the heating A/C section. Without a scanner here its not going to help you. So the fuse block pictured in the manual shows the top left fuse as the heater fuse at 10A and is noted on the block and in the manual as a 25A for A/C equipped trucks. Might try that but if you are not running a compressor and still blowing fuses then there is a short somewhere. Try isolating the motor first and see if the circuit is shorted before the motor. Might also try the same at the relay to isolate sections. Without a schematic it is difficult but possible to work through a circuit. My advise is to check the blower motor resistance. Then with the blower motor connector disconnected check the the motor circuit hot wire purple for a short to ground. think on this and get back to me.

[MacGyver72]

Thanks for the help. I'll check the wires tomorrow and definitely get some 25A fuses. I'll also see if there is anything else on that circuit that could be a problem.

[VetteVet]

Perhaps this will help.

[MacGyver72]

Yes. This is VERY helpful. thank you so much.

[MacGyver72]

Success! Thanks for the diagram V. I never did find the resistor which I suspected as the culprit once I saw it on the diagram but I was able to isolate all the wires to the A/C unit which is not there and even found a burnt wire. HMMmmmm. Once I got all of them away from metal objects, capped them off and tied them back, no more blowing fuses. Thanks a lot!!