I've been down this road before and it was always the module after testing every wire there is under the dash - under the air bag actually - and inside the vehicle which might sound all nice and cozy except it's on a 2000 Chevy Astro. Remember if you will that an Astro has NO foot room on the passenger's side.
I pulled it out, found out the warranty had been exceeded and figured 'Hey - I can bypass this High blower circuit and add some wire, a relay and a fuse holder'.
I found the command line from the blower switch on the dashboard and cut it off and added the relay and some associated wiring including an inline fuse holder.
"It's fixed" I said as I called my wife to try it for herself.
"No it's not - it's just as broken as it was before" as she was looking at me with that face that I bet gets stuck that way some day.
"Oh [email protected]! - I'll get back to it in a bit" I said and the truth be told - I totally forgot about it until every time I drove the van and I complained about the blower not running fast enough.
A year went by.
Just yesterday I decided that once and for all, I was gonna 'look into it' now before the first snows hit and I needed the fast defrost to work.
- I pulled the module and checked if it was any worse for wear since last time I saw it. it wasn't.
I checked to see that my fantastic bypass circuit was still the way I left it. It was.
I put the module back in and started probing the power to it in High mode.
Aha! There was no power going to the relay I had wired in. Doh!
Get ready for it.....................
I'll tell you .........
Here it is: The fuse holder that I bought had a 10 Amp fuse in it. The blower needs at least 20 Amps.
I put a 25 Amp fuse in it just for extra scrim. It's running - and all this after a year of not having High Blower mode at all.
Anyone else want to volunteer for Big Dummy Awards?