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The Primered Panther
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313 Posts
Discussion Starter · #1 ·
So I've managed to get my hands on this 2004 ZR5 with only 62,xxx miles. It originally came from NY (so road salt, yay! 馃槖), made it's way to GA, and now home to LA. It was very well taken care of and, other than the aforementioned road salt issues, looks to be in very good shape. It even still had the original battery jacket around an AC Delco battery. It's actually kinda freaky, how original it was. Since I got it about 6 months ago, I've had the occasional, random electrical issues pop up. Like one day, the radio and overhead console appeared to have lost power during a hour-long drive. After a cycle of the key, and maybe a battery disconnect IIRC, they started working again - haven't done it since (FYI, that was a few days after I installed an aftermarket headunit). The wipers also pretty much wipe at whatever speed they want most times. And typically, if you hit the mist feature, they will wipe for eternity on low. That is unless you hit the washer fluid sprayer one time; then it'll wipe 3 times and quit, as it should. I've read about the circuit board issue on the wipers, and the possibility of the multi-function switch also being the culprit. So, up until now, I've assumed one of those two things is causing the issue with them. But there are no outstanding recalls on it, according to a VIN search on GM's recall site. So I'm assuming the wiper board fix was done years ago?

Well now, the factory alarm (theft deterrent system, etc.) has randomly gone off three times in the past week, once during the day and twice in the middle of the night (fun times). When I was backing out of my driveway the morning after, the dome light was sort of flickered on and off like the door wasn't shut all the way, though it was. That all led me to believe it was the door jamb switch(es) - But I tested both of them and both tested fine. I read over on Blazer Forum that there is (probably?) also a switch in the door latches that sends a signal to the alarm as well. From what I can tell, that one is part of the latch. So I'm assuming the whole latch assembly would have to be replaced to find out if it's the problem.

After explaining all of this to a few people more 'experienced' than I, all said the BCM is bad and/or going bad. That possibility had occurred to me as well. But the fact that most of these issues (all but the wipers) show up for a short period then go away 1: makes it almost impossible to troubleshoot and, 2: If it was the BCM causing these issues, wouldn't it be one or the other...good or bad, on or off? I know some switches or sensors can sometimes cause intermittent issues. But I just didn't think something as complex as a BCM would do the same thing. Any helpful thoughts on the problem? Directions to go to next? Wires to chase? Thanks!
 

94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
Joined
1,466 Posts
Grounds.... check them all for corrosion.Take the battery and REALLY clean the contacts. And the wipers... it is most likely the board- look up the repair- its easy. All your fixes can be found thru a quick search here.
 

The Primered Panther
Joined
313 Posts
Discussion Starter · #3 ·
Thanks for the quick reply! Searching and researching is what I've done for 3 days now, on here, Blazer Forum, and general Google searches. I have 15 tabs open right now, including wiring schematics! :cautious: I found the wiper board repair several weeks ago, long before the alarm/dome light issue. I just haven't had time to take it apart and solder or replace it. And now that I've got another weird electrical issue that has popped up, I wanted to confirm/invalidate the bad BCM possibility. Also, I know I mentioned road salt a couple of times. But this thing is surprisingly clean on the underside for the most part. It's mostly a few body panels that have corroded, where you'd expect to see corrosion. A lot of it still has factory coating on it, albeit 16 years old.

As you pointed out @Jayhawke , all of the info I've found points at a variety of causes: loose/corroded ground(s), ground faults, loose wires not pinned all the way in a plug, unplugged switches, bad BCM, door jamb switches, door latch switches, the list goes on. I'm just trying to get other opinions on the most likely culprit (i.e. where to start looking). I don't want to go drop $$$ on a new BCM (plus programming labor) if it might just be a faulty door latch or a specific ground.
 

Registered
98 2.2 Extended cab, 2001 V6 Extended cab Sport Suspension, 2001 V6 Extended Cab 4x4
Joined
1,345 Posts
The 4th Gen Camaros had this same issue too. Well at least the 98+ models did and the culprit was a poor solder joint on a relay in the BCM. This relay would break off the board due to it's weight and would cause all sorts of weird things to happen just as you describe (other than the wipers). The fix was pretty easy and it just meant reflowing the solder. I have not had my BCM apart to see if this is a common construction method and issue as my truck doesn't do this. I have issues with the PRNDL and ODO screens turning on and off and that is usually a broken solder joint there as well so... I am going to put my vote in on broken solder joint in the BCM.

Oh and if I got a second vote... Grounds.
 
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