HVAC speed control

[chengny]

Thank u Chengny appreciate your response my apologies on the schematics as they’re kind of confusing for a guy like me but now that u marked them in color I understand now. On another note I realize my wiring is a mess thus the reason for me trying to fix it. Looks like the harness I picked up from the donor should work perfect! The wiring currently in the truck is plugged into the wrong terminals.

Now on to the installation, you mentioned the “bad medicine” butt splices, I have no choice but to splice the donor harness at the firewall where the current splice is. What do u recommend other than butt splice?

Jeez, I hope you haven't cut your new harness! If you didn't (cut it), use some WD-40 and a screwdriver to release the two hole grommet by pushing it back into the cab. Chuck your butchered harness. Pass the engine side wiring on the new one through the opening. IIRC, all the connectors will fit if you do them one by one. That grommet is actually made of three parts. There is the common main one with two holes. The RH hole accepts the "sub-grommet" containing the electrical wiring and the LH one is for the single vacuum hose (that goes to the intake manifold). The RH sub-grommet (I just made that term up and it's definitely wrong - so don't use it with any confidence) for the wiring is split and held together with a clamp. The clamp can be removed and the grommet opens up to make it easier to pass the wires through.

But if you have already cut it...you'll have to do like Roger suggests and solder/heat shrink each lead. If you have to, it's not that bad - there's only 5 wires.

 

[Marcos]

I got the wire harness in and all speeds are working however I blow a fuse under the dash whenever I switch to high speed. I’m assuming the bigger red wire that goes to the junction box might be the culprit?

 

[Snoots]

First go back to chengnys' post #12 and double check your wiring before you burn up a harness.

 

[Marcos]

just a quick update on this. Haven't really worked on the Blazer over the winter. I did have to solder in the splices, ended up using some self soldering butt connectors which seem to work great! Still blowing a fuse when I turn on the high speed so im going to check both ends of the main red wire that feds from the junction box. I have an extra one if I need to replace. From what ive read this red wire controls the high speed directly so I shouldn't have any other areas to check other than this correct?