No 4WD or heat/ac/fan

[BirchyBoy]

I've done some searching and can't find my symptoms. Everything was OK 1.5 weeks ago, but then it just stopped. Here's what's happening:

1) I started the truck a week ago for a trip to the airport and no heat or fan control. That was a fun 30 minute ride at 40 degrees. The controls light up when the lights are on but nothing happens. The rear defrost doesn't light up when pushed, nor does the recirc light. No heat change when running either.
2) When I turn the fan speed from off to different on positions, the "Service 4wd" light comes on in the dash. It doesn't stay on for all positions, but when it comes on it stays on until the fan switch is changed.
3) The push button 4wd isn't lighting up or working. That was OK previous to this.
4) I've checked all the fuses in the dash and under the hood. No luck.
5) I've removed the radio, 4wd control and heat control and reseated the connectors. No luck.
6) I went to the salvage yard in hopes of finding a heater control. No luck.
7) When I got back from my trip I checked the fuse. When I first started the truck, I think the recirc light came on but I could have been seeing things.

I thought that I had read elsewhere on this site that the 4wd controls and heat controls were somehow interconnected but I could be wrong. The "Service 4wd" light is off when the fan switch is off.

It might be unrelated but it's worth noting: the "Check ABS" light came on about a 3 weeks ago but I haven't troubleshot that yet. I took it to an auto parts store which tried to read the error log but none came up.

Before I order a new/used heater control, can anyone offer any ideas?

'99 Yukon SLT, AutoTrac 4wd

 

[BirchyBoy]

I pulled the heater control out again and am checking the continuity between posts on the fan switch. I'm getting fluctuating resistance on speeds "LO" but that's it. Will a faulty fan switch stop the entire heater panel from working?

 

[BirchyBoy]

I replaced the blower switch but no change. The "Service 4wd" light is lighting up when the fan position is changed. No recirc light, no a/c light, no fan. No 4wd, either.

I put the old switch back in. Any help would be appreciated.

 

[BirchyBoy]

I took it into the shop for diagnostics and the have determined that it is the ignition switch assembly, part #D1414D, is bad and needs replacement. They are quoting $180 for the part and $160 for the labor. I know the part is available on Amazon for around $90. How difficult is the installation?

 

[xanatost]

It's not hard to switch out but it's kind of a pain to get in there. You will need some small screw drivers. Just take you time and try not to get too mad lol

 

[BirchyBoy]

Thanks. I let them take care of it and it's done. The technician said that everything that wasn't working is now 100% again. It resolved the heat/ac issue, no 4wd and even the ABS light being on.

Since I had taken the heat/ac control out a couple of time, some of the tabs broke off, including the two on the far right side that holds the vertical flex harness in. Is it safe for me to run a piece of electrical tape over that connector to the top and bottom of the plastic where the tabs used to be? I'll plan on replacing that panel later this winter but need to recover a bit before putting more into it.

 

[BirchyBoy]

The truck is 100% better now. Here's a synopsis for those that care:

1. ABS light came on and stayed on most of the time.
2. AutoTrac panel was dead.
3. Heater controls were dead except for the fan. When that control was changed, the "Service 4wd" light came on but the fan didn't.
4. Rear air controls were dead.

The ABS light came on about 3 weeks prior to the other issues so I didn't mentally connect them as a single issue. The system did not throw any codes readable by the OBD system. The technician found 3 dead leads in the fuse panel. He troubleshot the issue to the ignition switch wiring harness.