Gremlins?? or not?

[Johnboy555]

I've been turning a wrench on my own cars/trucks for 50+ years but this has me totally scratching my head.

2005 Express 2500 extended wheelbase, 4.8L, 4 speed automatic. Basic utility setup.

Randomly.. the "anti-lock" light will come on. When this happens the A/C/heater blower motor shuts off. I can see no relation of heater/A/C and anti-lock brake sensor. It will last up to 10 min. or so and then back to normal operation.

Anybody ever hear of something like this?? Makes me nuts when it's 90+ degrees out. Any ideas as to where to start looking for solution?

Thanks!

[Blue Bowtie]

I had that on an Astro. The power distribution is suspicious. If the EBCM main power relay drops the warning light will illuminate. That same power interruption could be affecting the blower.

I've found several GM vehicles with problems in the UEC, including the power bussing and its connections.

The IGN-E fuse and ABS fuse in the UEC, and BRKS fuse on the body fuse block could be involved.

On the body fuse block, the BRKS fuse and HVAC control head fuse are both supplied by the ignition switch, Terminal J, to the fuse panel. If the switch or that wiring is failing, that could explain it too.

[Stealthee]

A poorly charging alternator can cause funky electrical problems. On some vehicles the ABS light will illuminate with the battery light letting you know there is a problem.

GM's of that era are notorious or ignition issues too.