So I have been driving my H3 for a few months now and now have a few questions. First off is the traction button. If I press the button nothing happens, or so it seems. No extra lights on the dash and nothing on the information center. If I press and hold the button the traction light comes on and the stability disabled shows up on the information center. Is it possible to only turn the traction off? Next is when driving at night and I come up to a stop and hit the brakes, the headlights dim for a moment and then go back to normal. Would this be the electric brake booster (Thank You Isuzu) or is something actually wrong here? I know Doc Olds will say something about the battery cables. Next is heated mirrors. Not sure if that is even on my truck. Is there a switch for the heated mirrors or is it integrated with something else? I had a Nissan Pathfinder and the heated mirrors came on with the rear defrost. Last is the blower motor. I know something is wrong here. It was on high the other day for a few minutes and cut out a couple of times and has been working fine ever since. Can't find the problem if it is working fine. Possible relay or heater fan resistor?

 

The lights are normal, you guessed it correctly. Heated mirrors were not an option, but would be a good one! Check the connector for the blower motor resistor behind the glove box, they give trouble and there is a recall on it (but no parts yet for a fix).

The stability and traction controls are complex. I do not believe that traction control can be turned off completely as you can feel that there is always something working in the background when offroad.

 

Thanks rsc. The info will be put to good use. I will probably get a new resistor and pigtail, if available.

 

If your lights really go dim also look at your rpms. If they dip down below 500 then it might be time to clean your MAF and throttlebody.

 

Thanks chooch. Those items, as well as a new set of spark plugs, are on my to do list. The RPM's do occasionally drop to 500 and pick back up quickly. it does not seem to affect the light dimming situation, which I will say is normal at this time.

 

The headlights should not dim when the engine is running. Hitting the brakes takes electrical for the brake lights, but if the charging system is working correctly, the brake lights should not affect the headlights. As Chooch said, if the RPMs are dropping real low, that COULD affect the alternator output, but no, it is not normal.

 

Hitting the brakes also takes electrical current for the brake booster. Not much, but as the vehicle comes to a stop and the engine makes it back down to idle the voltage dips until the alternator gets the signal to up the voltage slightly to compensate.

 

I guess we're gonna have to agree to disagree. If the system is working correctly, the voltage should never dip low enough to noticeably dim the headlights. The alternator/voltage regulator should never be outputting less voltage than the battery has, and even when you turn the vehicle off and the RPM/alternator output goes to zero, the battery should be at full charge (12.6 VDC) to compensate and cover 100% of the electrical needs (BTW, most people don't realize this, but a 12 volt battery at 12.0 VDC is at less than 50% state of charge).

If headlights are dimming noticeably when you hit the brakes, there is a weak link somewhere in the system that is not performing as it should; alternator/voltage regulator, alternator belt, brake booster, battery, battery terminals, wiring...something is not quite at 100%

I have an older (1988) 27' motorhome, that I pull a 20' enclosed trailer with electric brakes. Between the MH brake lights, the trailer brake lights, the electric trailer brake controller, and the electric brakes on the trailer, it pulls significantly more amperage when I hit the brakes than a Hummer H3 does, yet the headlights do not dim.

 

This is an old issue that has been discussed and resolved many, many years ago while the H3 was still in production. I don't care about what another vehicle does, the H3 is the system in question. The alternator in the H3 is not like they were back in the good old days, output is based on load/demand for fuel savings. Here are a few threads for you.

https://www.hummerforums.com/forum/h...-lights-23475/
https://www.hummerforums.com/forum/h...problem-13976/

 

Well, it may be somewhat common on the H3, but I still maintain that it is not "normal", as evidenced by the fact that only some do it. Mine does not. Many others' who posted also do not. Even the link you provided showed an owner that did extensive testing, while driving, under varied conditions, and saw only a 0.1 volt variation; not enough to cause dimming. THAT is normal behavior.

My Alpha has the same engine and trans as my wife's '06 4wd Tahoe LT. The computerized systems are no more or less complex on either vehicle. Neither exhibits dimming behavior, nor has any vehicle I've ever owned in nearly 40 years of driving, from a 1967 VW Baja Bug to a 2015 Corolla, unless there was a problem.

And the claim (in one of those posts) that the H3 alternator "turns off" during low demand periods is also wrong; output dips, but never stops. NO vehicle is designed to run off the battery only; a battery is there for starting. Once running, 100% of any vehicle's electrical needs are provided by the alternator, and if anything, a newer vehicle should be more consistent with providing the required voltage than an older vehicle. Computers react much faster than the human eye can discern.

If the headlights are dimming noticeably, something is not quite at 100%. Will it cause problems (other than minor annoyance)? Maybe not, but it is not right.

Failing battery terminals on the H3 are common, but they are not "normal". TRACTION FAILED/SERVICE STABILITRAC errors are common, but not " normal ". PO651 CEL codes are common, but... So unless you can point me to a printed response from GM saying it's normal, I guess we'll still have to agree to disagree.