Charging system issues & ???

[89GMCK5]

This morning on the way to work I noticed my voltmeter dropped from it's normal rock solid 14.5+ volts to right at 13.0 volts. '89 GMC Jimmy bone stock.

As I drove and was thinking about pulling over to check it out, it came back up to it's normal position. I continued on my way, as I pulled into work it dropped again. By the time I pulled in and parked, it was back up about 14.5. I got out, put a meter on it at the battery. Running at idle, 14.25- 14.4 volts at the battery on the line from the alternator, and ground on the neg bat post. Let it sit at idle for about 25 minutes, no change.

I cut it off, kept the meter on it. Voltage on the battery reads 12.7-12.8.

Any ideas why the voltmeter would drop like that? I'm thinking possibly my alternator is on it's way, bad ground somewhere, dunno??

Thanks,

 

[lectric80]

Grounds would be the first thing to check, next would be to start turning on loads. I would guess either the engine ground is on it's way out, or something kicked on and dropped it momentarily. It should compensate for a drop like that, but if the voltage regulator in the alternator is going out it could cause this. These are the hardest to diagnose because if you take the alternator to be tested it is most likely going to work fine, unless they test with multiple loads.

 

[89GMCK5]

Loaded

Yeah, I loaded it with headlights, interior, turn signals, brake lights, etc. everything I could think of, not much change maybe 14.2 or so. I had everything on except the A/C (which doesn't work anyhow, have a leak and compressor needs rebuilt / replaced).

The way it dropped and came back I am also thinking either the internal reg. or a ground is on it's way. I guess I can check the grounds real good and see how it goes. If it keeps up after that, I'm guessing an alternator is in my future.

The ground off of the alternator runs to the back of the block?? I know I have one at the radiator support by the battery.

Thanks,

 

[lectric80]

The ground from the battery should run to the alternator or real close to it on the block. Just remember, the main cables tend to rot from the inside out, so it might be worth it to replace the ground from the battery to be safe. I have seen ground cables that appeared ok from the outside, but the center area of the wire was badly corroded.

 

[diesel4me]

I'd suspect the dash gauge,few GM ones are accurate or reliable!...

I replaced an altenator in my 80 El-Camino once,and the dash gauge showed 12V,not the 13+ you should see if its charging properly...the altenator was a "good used" one I had kept from a parts truck that I knew was OK,so I started doing some investigation...I found the battery was indeed getting 14+ volts,even when the gauge refused to go much above 12V...I did a lot of wire checking,cleaned all the connections,battery terminals,checked for fried fusible links,nothing showed any trouble..

Then a friend came by one day,and I asked for his opinion,and he said "start it up,I bet its not your altenator--its probably the gauge"...I started it,the gauge goes up to 12V,and no higher--until my friend reaches in the window,and pushed firmly on the plastic cover over the fdash cluster--and I see the voltmeter's needle swing another 1/4" over towards 14 volts!...I "fixed" it by stuffing a penny between the dash cluster clear plastic cover and the dash itself,to hold some pressure on the cluster...all it was,was the printed curcuit behind the dash cluster wasn't making good contact with the pins on the voltmeter...

Most of the voltmeters in my other trucks always read on the "low" side--I just ignored the low readings as long as my tests showed the altenator WAS in fact charging...its just something you learned to live with,like the DIM dash cluster lights that seem to be 2 watts at night and you cant even SEE the gauges after sunset!.

 

[89GMCK5]

Thanks. Worth a shot anyhow, on the dash guage. I am going to try and trace everything this weekend anyhow and see what I can find. It's an '89 and could probably use a little tlc over that area anyhow. I plan on going over it all, just a little area at a time I guess we are going to start with the charging system this weekend.

Thanks again guys.

 

[Fordum]

Any idea how many miles on the alt?
I have seen them do that when the brushes get worn down and start cocking sideways in the holders.

Also, was it raining? Being a Ford guy, I'm not up on GM, but I'm pretty sure that you have the serpentine belt. If so, then its probably not slipping since you would lose power steering too.
But I have seen worn V-belts slip briefly when water splashed on them.

Otherwise check all the wires. Grounds certainly, but don't forget the big one on the back that goes to the battery.
It can get loose too.

 

[4xcrazy]

The '05 Avalanche here does this all the time, one time I'll look at the gauge it's reading a touch under the 14v mark, a few minutes later it's up in the 14.7 range. I've had everything checked out and even replaced the battery cause it left us stranded twice. Haven't really had any issues with anything NOT working, just weird. I would probably guess it's like Fordum says, an older alternator just giving weird voltages from old internal components.

 

[DizturbedOne]

Probably the gauge

Chevy electric gauges are... Not the best.

My Camaro is so jacked up. Every needle is all over the place lately. The gas gauge goes crazy in the 3/4 full range but is fine everywhere else. The oil pressure gauge reads MAX at all times. The temperature gauge reads 40 degrees higher than it actually is (that was scary first time it happened, LOL). The tach is about 200 rpm off at idle, and about 1000 rpm off by the time I get to around 5500 rpm... uugghh. I hate doing electrical work too.

I'm going to ride it until I absolutely can't get by anymore (don't know what anything is reading) and then just replace the whole cluster and the sensors with aftermarket stuff

 

[89GMCK5]

Well the truck has 155,000 on it, and if it's like everything else, probably original.

Yeah I thought about the slip, was damp but not raining. Belt is brand new, or 6,000 at the most on it. Didn't notice any other symptoms at all.

Looking around, advance $120 Remy Gold. Rockauto same price with no core charge, but shipping costs. Napa, Oreilly's, and autozone are all higher for off brand stuff. Anyone have other suggestions? Experience with the Remy's?

If I don't find any concrete explanaition I am going to replace the alt. and tensioner together. I've been looking into rebuilding it, and I do have the factory manuals but I can't find parts or a kit for it. Ideas here?

 

[89GMCK5]

Solved?

After just watching things with the voltmeter and doing some checking, basically waiting for something to either get worse or fail completely, I noticed a little bit of moisture around the power steering pressure line crimp at the pump. This is in very close proximity to the serp. belt. Not spraying out everywhere, but I could definitely see where the entire crimp was wet, and some of the drivers side of the pump / reservoir was also wet.

Long story short, I replaced the pressure and return hoses and 2 days of driving no fluctuation in the voltmeter. Was doing it every trip out until I changed the hoses. Could be a coincidence, but I'm thinking that the crimp would spray at certain times / pressures and wet the belt, cause some slipping, and the voltmeter would reflect such.

One thing I did learn along the way, troubleshooting with a flashlight in the dark at 4:30 a.m. sucks. You don't see the big picture.

We'll see if that was it.

Thanks for the help.

 

[Fordum]

One thing I did learn along the way, troubleshooting with a flashlight in the dark at 4:30 a.m. sucks. You don't see the big picture.

Doing most things under those circumstances sucks. Like walking out when you're stuck and not in your own truck with the big hydraulic winch..........

Told that idiot not to go down that road, but noooooooooooooo!!

 

[89GMCK5]

Well while my voltmeter has been holding steady for about a week now give or take a day or two, this afternoon I get in and start it up. Hear this clicking noise faintly from the tailgate, drivers side.

Turn the radio down and listen some more. While I'm listening I am watching the voltmeter, with every "click" at the rear the voltmeter drops to about 13 volts. WTF.

Just about to get out or climb to the back and take the access panel down when I look at the effin rear window switch. That mf'r is just sitting there staring at me STUCK half way over like it's engaged (depressed)to the passenger side.

Now the rest of the story, my tailgate has not worked since I bought the rig last May. Someone did a number on it. Visually it looks okay, glass is good, but someone either got rear ended by a high bumpered rig, or more liekly they backed into a tree. Regardless the outer skin is pushed into the window basically. It used to go down about half way but stopped late last summer. Oh, and also because of the damage the hinges are fubared to the point I haven't dealt with it yet. I am afraid that once I get it open I'll need to fix it or it will not stay shut again.

So what's been happening all this time, is the tailgate and it's messed up hinges have been bouncing on and off the safety switch, which is completeing the circuit for the power window motor (because the switch was stuck), the heavy load due to the bad motor was loading up the system.

So this weekend I guess she (K5) has decided I will start the tailgate project.

Thanks for all the help though guys. I appreciate it.