Check charging system warning and battery light

[Underdog66]

Hi all!

My 2005 Expy is displaying the check charging system warning along with the red battery dash light. It doesn’t come on until the engine has been running for a few minutes. It goes off after 10 minutes or so of driving and comes back on after another 10 minutes or so. They cycle repeats until I get home. I only drive a short distance to and from work, about 30 minutes one way.

I usually keep a battery tender on the truck as I hadn’t been driving it regularly up until 2 weeks ago.

The following are the steps/tests I performed today to determine the issue.

1. I ensured the battery was fully charged by leaving it on the charger while I was at work. I drove a different vehicle to work today.
2. When I disconnected the charger I measured the battery voltage with the truck OFF. It seemed a bit overcharged at 13.1 volts, so I leveled it off, per Eric The Car Guy, by turning the headlights on until it dropped to 12.5 volts.
3. When I turned the headlights on there was a noise that sounded like air leaking or a motor winding, coming from the area near the windshield washer reservoir and battery. The sound just faded away. I turned the headlights off for a few minutes, then turned them back on and the sound did not repeat itself.
4. I turned the headlights off, started the truck and measured the voltage at the battery. The meter indicated 14 volts. I idled the truck for about 5 minutes WITH the headlights on and then the dash warning came back on.
5. I turned the headlights off and left the truck running. I measured the voltage again to find it had dropped to 12 volts.

Is it possible that it's the serpentine belt? Once the engine was off, I tried to pull the belt off WITHOUT releasing the tension. I was almost able to pull it over the pulley on the alternator. My thinking(which might be flawed) is that when the belt gets warm, it stretches and no longer turns the alternator efficiently.

Also I replaced the power steering pump last month with I changed the rack and pinion. Is it possible I put the belt back on wrong?

I’m not too familiar with how alternators work. Maybe that’s how a failing alternator works too. Good and strong at the start, but weak once its warmed up?

Any input is valued. I have been able to keep this 20 year old truck running with help from you all here.

Thanks!

 

[whtbronco]

The battery voltage seems okay to me. I would think you'd hear the belt slipping(squealing or chirping), but maybe it's slipping and not loud enough to hear it. If the belt can be moved that easily I would start there and it would fit with your intermittent symptoms. At this age your belt tensioner spring is likely not as strong as it was 20yrs ago. The belt could have stretched out too.

One thing I do to test battery voltage is put a multimeter on the battery while having someone start it. With a bad battery voltage usually drops to 9v or lower. I don't like to see below 10v. The alternator should put out 13.5-14.5v.

This may help with identifying if the belt has stretched too much, assuming you have a the factory belt tensioner.



Here's the belt routing:

 

[Underdog66]

Thank you for the input. I ordered the belt, tensioner and alternator last night. I suspected the belt and was going to replace that first. Amazon suggested replacing the tensioner at the same time, as did a coworker and yourself. The alternator was only 90 bucks free shipping and returns. I figured it be good to have it on hand just in case. The other item I'm going to check is the new power steering pump, since the issue showed up after replacing it.

I appreciate the images of the tensioner and the belt routing.

 

[Underdog66]

@whtbronco Its fixed. I tried the belt and tensioner first. My neighbor, who's a diesel mechanic, 'helped' by giving me advice and standing next to me. LOL. He was just getting over pneumonia and didn't want me to get it. But I digress. Once I started the truck he held the meter leads on the battery. It read 14.5 volts for 2 seconds. Just as he told me that I saw the warning on the dash and the battery icon.

I shut it down and removed the belt. As I unloosened the alternator bracket bolts one SNAPPED. Luckily it was one in the dead alternator. When I tried the lower bolts they were stuck. Since I had broken the bracket bolt, I was gun shy to reef on them. I soaked them with P'Blaster for two days and applied heat. I tried the first day but still felt the bolts would break. The second day my wife STRONGLY encouraged me to use the breaker bar. We discussed the possibility of one or both breaking and decided it was worth the risk. I was able to turn both bolts a little bit. My neighbor suggested tightening the bolts back up and then loosening them. I did this back and forth until there was enough clearance to lift the alternator up and out.

Once I got it all back together (or so I thought) I started it back up, only to have the warnings come back on the dash. OH CRAP! My wife immediately said, oh no, it was the battery after all. I got back under the hood to remove the battery only to see that I hadn't reconnected the alternator cable!
Its all good now!
Thanks again for your help and encouragement.

 

[whtbronco]

Outstanding and well done.

Thanks for following up too.