Heater problem

replaced blower motor resistor on my wifes truck and lasted two days. bought another one and lasted about a month. heater only works on 4 setting when resistor goes out. what is causing resistors to keep going out.

Your blower motor is dragging. It’s drawing too much current for the amount of air that it puts out, so the resistors are burning up. You need to replace the blower motor (and the resistor again).

It could be the motor itself. Maybe a baring is going out. However I am a little confused by your description. Let’s tell us about exactly what is happening and when. What speeds work when.

Example: 1, 2, 3 work but nothing on high (4) Or maybe 2, 3 and high work but not 1.

when working fan seems to work fine. no noises or anything. if i spend the fan by my hand it seems to spin fine with no drag whatsoever. when resistor goes out fan only blows on number 4 setting and no other one. all speeds worked fine after i put in second resistor for about a month and now it went out.

I dont see any mention of what year n make this is

2005 gmc canyon 4 wheel drive 5 cylinder. read on a website about the pigtail that plugs into the resistor being burnt on some trucks and having to be replaced but mine looks fine. people on website seem to suggest that this is a common problem on these trucks but like i said mine seems fine. no burnt marks or melting or anything.

As noted, this is common when the blower motor is drawing too many amps. Its probably what blew the first resistor.

i dont think its the blower motor because of above reasons.