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Thursday, February 21, 2013

2004 Chevrolet Tahoe, 30 Amp Blower/HVAC Fuse Blows

Hi Sparky,

Every time I put in a new 30 amp Blower/HVAC fuse it blows as soon as I turn on the control knob on the dash. I have already replaced the blower resistor and the connector that goes to it. I have now removed the blower resistor and cut off the harness trying to isolate the short. I then tried installing a new 30 amp fuse. It still blows this fuse as soon as I turn the blower knob to #1. It blows the fuse even though no resistor or it’s harness is connected. No wires are touching where the harness (Connector) was cut off. Could the problem be in the HVAC control head on the dash or maybe the relay under the hood?

Hi Nick,

Since you stated it was a 30 amp fuse I am assuming it is located at the driver's end of the dash. I would narrow the problem down by installing a new fuse with the key off. Switch the blower switch to speed 5 and then turn the key on and see what happens. I would repeat on each speed in the same manner. Doing so will hopefully tell you if the problem is with only one speed or with several. This will give us a direction to go in to look for the short.


Thanks Sparky,

I did what you said and it worked on speed 5 and then 4. As soon as it hit speed 3 the fuse blew. Key off Replaced the fuse and pulled the temp control head on the dash . I then Checked each wire for continuity to the distant end at the module connector. I found the yellow and tan wire to be conducting to each other and to ground. I then slowly traced the wires back to the module and further on to the large connector at the passenger side access panel on the dash. This connector had several female connectors grounded to each other and to ground as I checked it with my meter. I began unwrapping the tape on the wiring harness behind the connector because the connector appeared to show no damage. About 6 inches from this connector, I found several wires melted together. I cut them out and soldered and shrink tubed them and taped them. Everything works fine so far. I am a little worried about how the wires became melted in this manner. I also noted that prior to reinstalling the blower resistor, it was hot to the touch. I hope this is normal. I put everything back together and on the way to work this morning everything works, all 5 speeds.  Thank you for you direction and help.


Hi Nick,

Although I have never seen it, I have heard of an issue of wires rubbing on a bracket around the glove box area.  

The blower resistor is designed to have air flowing across it to keep it cool. If it was not mounted it would get very warm. If  left long enough it would get hot enough to burn you and cause internal damage to itself.


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