Another heater issue

[Jumpmaster]

So my heater only worked on high. the switch was good so I replaced the blower motor resistor, still the same thing. Just got the blower motor relay in stalled and as soon as I turned it on it blew the heater fuse. Anyone have any insight as to what would cause that? 84 K5 350/700R4/AC.

 

[Jumpmaster]

Replaced the fuse and blew it again with the new relay. Put in another fuse and the old relay and it works, but still only on high.

 

[Jumpmaster]

New relay was bad. Bought another and it now works on all speeds.

 

[British Slave]

 

[CGT80]

I bought a new relay for mine and it blew the fuse also. turns out it had a resistor? in with the relay to help reduce voltage peak (looked it up on the net) when the fan is turned off from hi. The old relay did not have that part. I opened up the relay case and cut out the offending item and the new relay worked.