NEED HELP Alternator or something else?

PProph

Original poster
Member
Dec 7, 2011
220
'03 Trailblazer LTZ, 272,000km. Routine maintenance though I haven't been as vigilant in recent ages. Have done plenty of work on it over the years though as evidenced in other threads of mine.

About a month ago when we first dipped into frigid temps (-20 C) I had it sitting for a couple of days and when I went to use it again it wouldn't start. Boosted it with a back up booster pack and off she went. I made a note that it might be time to change the battery, it had a 5-year warranty when I bought it in 2012. Being the proactive person that I am, I forgot about it and went on about my daily life. Fast forward to a week ago, we had -30 plus windchill. I had it plugged in (block heater + interior warmer), started it and it fired up. Was warming it up and brushing snow/loading up when I noticed that the interior light was off. I thought it had timed out because I left the door ajar but when I tried to turn the interior lights on, nothing. Then realized that the headlights had gone out as well as the instrument panel. Figuring that I did have a weak battery I tried running higher RPMs to get the alternator running a little higher. Lasted about 30 seconds and the whole thing up and died. Wouldn't start again.

We put a bigger charger on it for the allotted time, still wouldn't start after that.

Luckily I was at the in-law's farm and he had a vehicle to loan me and said he would put a new battery on it. Fast forward the next day he picked up a new battery, started right up but battery light was on and warning said battery not charging. He tested voltage and it said there wasn't any charge. So our thought process here is battery and alternator should both be replaced, I've been pricing out waiting for the holiday season to be finished/warmer weather which we finally have.

So today it's up to -7 C, and wouldn't you know it he started up the TB and says the alternator seems to be working today.

Is this an alternator on the way out? Bad connection or ground somewhere?

I don't really want to replace it if it's not the problem. I did have it out about a year ago to replace the T-Stat, as far as I know everything was reconnected properly.

Looking for some feedback on this, seems to run/charge fine except in extreme temperatures. We've replaced the battery regardless.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
If it's the original alternator, I think you're on borrowed time. Cold makes things work harder and that probably was beyond its current ability. I'd replace it.

BTW, if you can wait a few days, check out the prices on Rock Auto and Amazon compared to local. Even with shipping, prices are pretty good. And if you get a new one instead of a rebuilt, you won't have to return the core.
 
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Reprise

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Jul 22, 2015
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Mooseman is likely right - extreme cold stresses parts, and your alternator is probably feeling it, w/ 272K on the clock.

When you put in the new one, charge up the battery (if needed) before starting up the truck. Making an alternator charge up a nearly dead battery also stresses it - and sad to say, I don't think the new one will be built to last another 272K. Although I'd certainly look at another AC Delco / Delphi - I'm surprised it lasted that long, TBH.
 

PProph

Original poster
Member
Dec 7, 2011
220
It's a Delphi and I assume it's the original, at least I've never changed it, but I'm not the original owner, bought it around 150k.

Thanks Mooseman, and I'm well versed in RockAuto, I'll pay half of what it costs local, even with shipping from US. The father in-law has an 02 Envoy on the farm that we might borrow the Alternator out of, although it might be even older lol, pretty sure that one's well over 300. I suppose if the Blazer's running and we've got a warm spell here I might take it to PartSource and have them do a bench test on the Alternator.

Also the battery is new so won't need a charge.

In any case, thanks for the feedback, I'm fine with changing it out (even that stupid bottom bolt) I just didn't want to be doing it for nothing.

Been driving the in-law's Explorer, fun gadgets but I'm really not familiar with/a fan of Fords it would seem. I know most of it is preference but I can't say I'll ever head down that direction.
 

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