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TB Electrical System On The Fritz

1476 Views 3 Replies 3 Participants Last post by  rbarrios
Okay... I'm driving a 2005 TrailBlazer LS/EXT, 6-cyl, 4WD. Has performed pretty much flawlessly since I bought it new in 2005.

HOWEVER... In the last month, there have been some peculiar problems. First of all, my air conditioning fan control suddenly lost its maximum setting (setting 5). Just stopped blowing altogether on 5. About a week later, it lost setting 4. So now my maximum fan setting is 3.

Aside from the AC control, everything else seemed fine.

Then, three weeks ago, I drove down to fill up the tank, and when I tried to start the truck afterwards, nothing happened. Absolutely nothing. Like it didn't even have a battery in it. I had to get it towed (for the first time ever) to the shop, where they quickly diagnosed...a completely dead battery.

HOW does a battery go from cranking instantly on one bump to completely dead in less than 10 minutes?

Anyway, I had a new battery installed, and everything seemed to be fine (except for the AC controls, which were still screwed).

Then, about a week after the battery incident, I drove the TB to near empty and got a low fuel warning. No prob, I filled up the tank, cranked the truck afterwards, and the gas gauge went haywire on me. It showed the tank was still empty (warning chime and everything), but a few minutes later the gauge jumped up to a quarter-tank. Thirty minutes later it jumped up to full. It's been jumping up and down ever since, so I have to rely on the odometer.

This sounds to me like several electrical problems with a common source, possibly.

Any ideas?
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All separate issues. Sorry.

Batteries can spontaneously go dead from a broken internal connection to the post. Usually from a bump. Rare, but it happens.

The fan speed control issue is without a doubt your blower resistor pack. Run a search and you'll find a thread with pics of how to change it. Under $50 from the aftermarket parts stores - it's up under the dash behind your glove box.

The gas gauge level is an unreliable design of the sending unit, inside the tank. Lots of labor to drop the tank and replace it, but again, there are members here who have done it, with pictures. Search.

Are you a DIY kind of person? You'll save a lot of $$ if you are. Or if you have a trusted non-dealer mechanic.

Thanks for checking here, though. We owners know the platform a lot better than most mechanics who don't work on them as much.
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Are you a DIY kind of person? You'll save a lot of $$ if you are.
Yeah, I'm a DIY agent. I hoped somebody out there could diagnose these symptoms before I had to take 'er in for a real diagnostic.

Okay, cool, I'm totally down with whatever you say, man. If these are all separate electrical issues, good deal. Pick 'em off like fleas.
the Roadie is right... these are all SEPARATE issues- and not connected to each other in any way--- they just happened to occur close toghether.

the fan- the resistor module is bad- its about $25 and takes about 15 minutes to change- theres a HOW TO on here somewhere.
No need for a mechanic on this one......

My battery died on me suddenly. was working fine- Cranked fine
I did notice my voltmeter needle moving a little back and forth...
I parked- went inside for 5 min. came out-- crank-- nothing- totally dead.
Went to get new battery-- VroooooM...

As for your fuel level sender....
There is a REMOTE possibility that running a bottle of Techron will help clean sulfur buildup on the contact points. A few have reported this works.. most say it does not- the side effect is that it cleans your injectors too.
If you know what your TB gets- MPG... then you can live with the bad sender..
just fill up--- reset trip meter- and use that to judge when youre running low.
If not- then depending on how many miles are on your TB-- you may want to replace the entire fuel pump/level sender.. (are you 100,000+)?
if not then you may want to do what others on here have done and do the work themselves.
Ill thell you-- that My sender was not bad- nor was my fuel pump--- but at about 134,000 I decided to drop my tank and replace the fuel pump/level sender.
the price was about $350 to do it myself.
I called dealer out of curiosity- and they quoted me $1200.
If you do plan on doing this yourself- or mechanic--- drive the vehicle till its practically running on fumes... dropping a tank that is full of gas is not fun.
I drove mine for about 35 miles AFTER the light went on...
sure enough I dropped a tank that had very little fuel in it... this made for easier manipulation of the tank...

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