Yes we have ground at the relay.

 

With the connector plugged into the relay back probe OG(orange) to check for ground.

 

We have ground on the skinny orange wire but not on the fat one.

 

You should get (-) ground on both orange wires when rotating the HVAC blower speed control. Inspect/clean all connectors/contacts.

 

Which wires carry the + from the battery to the bm? I'm not following this chart. If I add + to the brown wire the fan works on the 3 lower speeds.

 

OK I am now convinced that I have a + power problem somewhere between the fuse box and the BN brown wire. If I jump from the + battery to the BN wire in the harness the blower works on all speeds.

 

according to the wiring diagram a few posts above BN feeds through a relay and then goes to 2 fuses before reaching the motor and yet another relay. keep following the voltage from the source.

 

Thank you so much for all the great info and troubleshooting advice. This thread should be pinned.

ted

 

I wish I had seen your post before I started a new thread: https://www.hummerforums.com/forum/h...aps-out-46014/ I spent a few hours trying to find my blower problem and ended up having the same problem you did. With all the HVAC problems due to connectors melting it looks like the design wasn't robust enough.

 

We did not find the actual problem but pulled the 30 amp fuse, installed a new wire from the fuse spade through a new 30 amp fuse then all the way to the brn wire in the harness behind the glove box.

It works as it should now, we have all speeds and it shuts off with the ignition. There is a problem with that brn wire but it is 100 outside and we needed it to work. May continue searching for the break in the fall or may just leave it as is since we did a good job with solder and shrink sleeves etc.