Service 4wd message comes on when I turn on AC??

Discussion in 'General Chevy & GM Tech Questions' started by steelfoxdesign, Aug 11, 2012.

  1. steelfoxdesign

    steelfoxdesign New Member

    I can't figure it out.. I feel like there is an electrical nightmare going on in the truck and many searches have turned up nothing exactly like what I'm experiencing. First off, the voltage meter is always dropping whenever you use the power windows, brakes, ac (especially! from like 14 to 10), and all the interior lights dim and if you use the windows, and the dash will display the ABS light and cause some other lights to come on when the voltage drops too low. The AC works fine when its on and while you are driving, but at idle, it slows down and will sometimes blow warm air.. The service 4wd message comes on only when I use the AC and it engages fine when its not on, I haven't tried to engage it when the message is on, but I assume it would work anyway. I've checked the battery connections and alternator ground but I'm not convinced that's it. I also believe that its not the alternator, because they usually work or they don't, and mine's working for the most part. There is an aftermarket radio installed (with a wire that goes into the drivers side fuse box jumped off of a fuse? which I think is weird) and the whole dash cluster was replaced with a new one right before I got the truck. Any thoughts on what might be happening here? I'm pretty mechanically inclined and do most work myself, but I'm not an expert, especially when it comes to electrical stuff. Thanks for any insight!
  2. Kady

    Kady Epic Member 5+ Years GMTC Chick 100 Posts

    Firstly, You should post what year, model, trim, engine size and if its 2x4, or 4x4 in your sig just to help us know what you're driving... Have you tested your battery lately? Local auto parts store should be able to do that for you. Or maybe your alternator is junk, sometimes they do crazy things up until the time they kick it. Or maybe the Serpentine belt? As far as the Service 4wd, my truck has been doing the same thing. I just haven't gotten around to checking on it.. I've heard the switches were just poorly made, You can either get a new one, or clean up and resolder the wires in the old one to save some money and try to eliminate the problem.. How long have you had the truck? Has it always done this? Does the Service light come on immediately when you turn the A/C on?
  3. steelfoxdesign

    steelfoxdesign New Member

    I put all that in my profile, didn't realize it doesn't show up if not in the sig. I'll add it there too. I haven't checked the battery but I will, I want to get this fixed! The truck is very drivable but this problem has been aggravating me for some time now. The alternator has to be removed to be tested, kind of a pain in the a**. I've heard the switches are bad too, but the all the lights function, and it will put it in 4wd. I got the truck in February of this year, and it has 130K on it. The service light comes on within 30sec of the AC being turned on. I think I need to do a load test on the electrical system but the auto parts store doesn't do it and says I have to pay for it somewhere.. Would like to believe that it is just the switches but with everything else going on, I doubt it somewhat. Thanks for your reply.

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