Fan wont blow on high.

[Boyd Crowder]

First off, I have searched, believe me I really did.
I have a 1995 GMC K3500 Cree cab. The fan dtopped blowing on high, blows on all other speeds with no issue. I have replaced the blower motor resistor, twice, I have replaced the HVAC control unit with a new GM unit. I even replaced the blower motor itself.
Sometimes the fan will blow on high for a few minutes, then stop, most of the time it wont blow on high at all.
Its sooo HOT here I need to figure something out. Any help would be greatly appreciated

 

[magimerlin]

Check your wiring at your resister. I can not tell you how many I've replaced for custemers because of the same issue. The plug gets way to hot and melts/burns up.

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

[Eveready]

Sounds like a bad connection of some sort as the high speed should not be affected by the resistor at all. The resistor is intended for the lower speeds. That would agree with what Magimerlin says. If you remove that resistor after running it and that socket is hot then you probably have found the problem. I would like to know what should be done to replace it . It might be that a very small file could be used to clean the inside of the socket.

I am headed toward replacing the blower motor and when I do I only want to tear it down once. I plan to do the big clean out at that time and if any electrics need attending to that would be a great time to do it.

 

[east302]

Here’s the diagnostic for a 98 for a blower not working on high. It is probably the same for the 95. The blower relay may be the culprit. Hope this helps.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Sent from my iPhone using Tapatalk

 

[Eveready]

From that schematic I think you are right. I had no idea that the relay bypassed the resistor but it clearly does. If the relay is dirty or corroded it would display intermittent operation just as the OP describes.

How hard is it to change out as that looks like the easiest test for the relay? To test the blower you could run a direct hot wire from the battery to the blower. If it runs full speed then it isn't the motor.

 

[Kaiden]

So I’ve got the same problem I’ve replaced my resistor, climate control switches, blower motor, and relay. Every fuse under the hood in the dash and even the cigarette lighter fuse it has a good ground and it still won’t blow on high any one know what’s up with it?

 

[Schurkey]

So I’ve got the same problem I’ve replaced my resistor, climate control switches, blower motor, and relay. Every fuse under the hood in the dash and even the cigarette lighter fuse it has a good ground and it still won’t blow on high any one know what’s up with it?

WHAT VEHICLE?

Down load the appropriate service manual set for your truck, look at the wiring diagram for the blower motor. May be the same/similar to what's posted previously.

Perhaps a moderator will move this thread out of "Engines" and into OEM and Custom Interiors; or maybe Audio + Electronics.

 

[Banshman]

My 05 Silverado did the same thing, I replaced I believe the rheostat near the blower fan, also the plug was melted, I replaced all parts with a kit online that included heavier gauge wiring

 

[deadbeat]

I've fixed a few that wouldn't run on high, usually something simple if you can use a test light. The hardest one I fixed had a fusable link or something in the red wire that had corroded and broke along the firewall, thus not letting the relay ever get power.

 

[96blackswb]

I've fixed a few that wouldn't run on high, usually something simple if you can use a test light. The hardest one I fixed had a fusable link or something in the red wire that had corroded and broke along the firewall, thus not letting the relay ever get power.

My 96 Silverado RCSB was doing the same symptoms as you guys described and it was the red wire right at the connection under the glove box. It melted the connector on the red wire. Just wondering what would cause this and how do I prevent this from happening again