2000 Denali slowly losing power while driving

[Skweez]

I've been recently having starting issues with my 2000 Denali. At first I thought it was the starter so I replaced the starter. It continued to have starting problems sounding like it wasn't getting enough power. So I charged my optima battery overnight and it started fine. As we drive the gauge shows that we are losing power as we are driving. So I figure alternator replace that and the wires for starter and battery. Then I do a parasitic drain test and it shows that I have a draw of 0.04 when my multimeter is set to 10A. Any ideas I'm at the end of my rope with the electrical issues with this truck. Had major BCM for a while finally that was resolved now this.

[Jsdirt]

What's the battery voltage when running? Should be between 13 - 15v with everything on - lights, heater, wipers, ect.

 

New alt. could be bad - wouldn't be the first time I've seen that ...

[O_J_Simpson]

Where did the new alternator come from?

[Skweez]

Had the alternator tested it's good. It came from autozone but I had it tested 2 different places. When running it's shows about 14-14.5. Haven't tried with everything will now. I'll post results. Do you think it could be the voltage regulator?

Oh yeah and my gauges on my dash are bouncing around a lot like vibrating

[Skweez]

It's reading 14.2 - 14.5 with everything on and runningo

[Jsdirt]

Sounds like you've got a bad connection somewhere. Double check battery connections - make sure everything is tight, then double check the alternator wiring - maybe something was left loose.

[Skweez]

Pulled all the wiring replaced it all checked all connections and everything looks good. Going to drive around and see how it runs will post results when I get back.

[O_J_Simpson]

Had the alternator tested it's good. It came from autozone but I had it tested 2 different places. When running it's shows about 14-14.5. Haven't tried with everything will now. I'll post results. Do you think it could be the voltage regulator?

Oh yeah and my gauges on my dash are bouncing around a lot like vibrating

The Vatozone alternators are some of the worst on the market. They will test good at times but as soon as they get warm start causing issues.

[Skweez]

Just picked up a power probe 3 master combo kit. This should definitely help me find the problem. I just don't want to make anything worse. I've worked mostly on older vehicles and my Denali has different modules that I don't want to accidently run power through and mess up. This power probe tool set is hooked up. Power Probe 3, ect2000 wire harness probe and smart signal transmitter, with all the hook ups. Anyone familiar with these tools and have any suggestions on how I should go about diagnosing my problem? Thanx

[Jsdirt]

You have to know circuit design when using one of those, especially if you need to feed power to a wire to check operation. If you feed full 12v to a pull-down design circuit, you'll smoke the computer driver for that circuit. BAD news bears ...

 

Before you go crazy testing all kinds of things, I would load test that battery. Could just be the battery has a dead or shorted cell that isn't showing up until the vehicle has been running a while. You can have perfect voltage, but if the battery cannot supply it's rated amperage, all kinds of crazy things will happen on modern vehicles. Maybe just running the starter to fire it up is enough to start the downward spiral of the battery when it's running.

 

I'm willing to bet after re-reading this entire thread that you've got a bum battery.

Edited February 7, 2017 by Jsdirt

[Black02Silverado]

Go back over your grounds, take them off clean them up and put some dielectric grease on them and put them back on.

 

I also always rebuild my alternators and starters. It usually cost less and at least you know it fits properly. I had to have mine rebuilt, cost me $75 and a new one from Car Quest was $180.

[Skweez]

At first I thought it was the battery but then we had a friend who bought a brand new battery and let us drive around with it. After about 2 days her battery started having the same issue. Our original battery is an optima red top and we've had issues since we bought it. We have a 3 year replaceable warranty but O'Reillys won't replace it. It's never really held a charge but maybe that's because of what's going on now. Thanks for the help.

[Jsdirt]

Go back over your grounds, take them off clean them up and put some dielectric grease on them and put them back on.

 

I also always rebuild my alternators and starters. It usually cost less and at least you know it fits properly. I had to have mine rebuilt, cost me $75 and a new one from Car Quest was $180.

That's the best way to ensure a failure free alternator or starter these days.

 

In 2007 I bought an alternator for our '86 Grand Marquis. Should've kept that OEM one instead of buying this reman in hindsight ... but I got over 7 years out of it (OEM lasted 21 years). I still had the receipt when it failed, so I brought it, and the battery back to AutoZone - got a new alt., and got a few prorated dollars back on the battery. Bought a new battery from Interstate, and headed home. Not 2 weeks later, battery is FLAT. Not even 1 volt! So I charge it back up, and notice the battery light is on in the dash - key off, engine off! Had a bad diode in the regulator.

 

Tried to return it, but the dummies at AutoZone couldn't get the concept that just because an alternator CHARGES, doesn't mean it's GOOD. Excessive AC ripple will cause all kinds of problems on new vehicles today. Mine was just flat shorted.

 

Bought a used regulator on eBay for $14, and it's been fine ever since (3 or so years now).

Edited February 7, 2017 by Jsdirt

[Black02Silverado]

I understand that some do not have the option of getting their alternator or starter rebuilt but I feel it is the best route to take.

 

The place I go to has been in business for over 45yrs and the gentleman that own and operate it know their stuff. So if you have a place like I do, find it, ask around and go there. Well worth it.

[Skweez]

So now I'm pretty sure the problem was because of my BCM shorting out again. This will be the third one in 4 years. I put dielectric grease on it replaced relay on one of them also and it worked for almost 2 years. I just got used to it working and forgot to check on it regularly and now the circuit board is fried. My new question. As long as I have wire diagrams and or pin layouts, how difficult, if possible at all, would it be to wire in a BCM from a 2001 chevy suburban? When I was online looking for replacement BCM's for my 2000 Denali it brings up the same one I just picked up from a suburban is the exact same one. But the connectors are different more wires on the new one. And does anyone have a link for the diagrams or know where I can find one? Thanks

[Skweez]

Oops forgot to add anything when I hit post

Edited February 13, 2017 by Skweez