97 suburban squealing problem

[ccarlson]

Ok, I've tried everything I can think of and need some input. Here's the long details in hopes someone can help.

1997 Chev Surburban parked most of the time just used for towing about 6k miles per year. 146K miles on the vehicle. Runs and drives great except for this problem.

Last summer it would squeal when I started it if the A/C was on. Would stop the sound once I gave it a little gas or shut the A/C off.

This fall I blew a couple fuses when using the turn signal both with and without a trailer attached. Put in a real heavy fuse and noticed the battery voltage guage would dip way down when I used turn signal and squealing would start. Problem stopped once I shut off turn signal. Took it to a mechanic who did some searching and said he found a loose ground for the turn signals. He also replaced the Serpantine belt. Problem was mostly better for a while. The battery was due for a new one so I replaced the battery.

Now the voltage drop and squealing has reared up worse than ever with several other things triggering it, namely the defrost is on and any extra draw from anti lock brakes etc. happens. When the anti lock brakes kicked in at icy intersections, it starts squealing and continues squealing even after I let off the brake and give it gas as if the fuel pump extra demand from accelerating is causing too much draw as well. As I said, it is worse if the defrost is on but sometimes it will do it even with the defrost off. When the squealing and voltage drop occur, I have to drive about a half mile, shut off the defrost and heater fans and still wait for the squealing to stop even after those items are off.

The squealing does not look to be from belt slippage from what I can see and I've checked the temp of the belt and all roller wheels for hot spots right after an occurence with nothing noticeable.

Today I replaced the alternator thinking it had to be the beginning of alternator failure. New Alt installed and it still does all of the same things. Checked the battery terminals and the ground connection to the vehicle sidewall right next to the (-) battery terminal.

Any ideas? In my mind the main triggers seem to be the defrost/AC and the antilock brakes although accelerating from a stop seems to make the squeal even worse for a while. My concern is that the squealing/voltage drop doesn't stop once I am off the brake and shut off the defrost/AC.

Voltage is good at all other times.

Thanks for the help and sorry for the long post. Hoping to avoid another $150 of shop time spent searching for a short.

ccarlson

[Macgyver55]

Does the tensioner have good pressure on the belt?

Seems like any large draw is causing it to squeal and the lights were a different problem.

Also, if the pulleys have rust or corrosion on them from sitting a lot, the belt tends to slip easier so make sure they are clean.

[ccarlson]

The pressure felt pretty good when I released the belt to replace the alternator but I can't say for sure it is enough. But, I did notice a little vibration in the short distance of belt between the tensioner and the alternator. I wish the fan blades weren't so close to the tensioner. I would add a little pressure to it with a wrench to see if the problem stopped. Might see if I can make that work.

Thanks. Any other ideas?

ccarlson

[BoxMN]

Sounds like maybe the a/c bearing (or something like that, can't recall the exact name my mech called it, but not a big job, and he said I could do it myself, but I let him do it). I had similar thing in my 98 malibu. My fav neighborhood mechanic said he knew right away what it was by the description (squealed if defrost or a/c was off, no squeal when it was on), and he said just run it with a/c or defrost and it won't squeal, his Mom was doing it for about 5 years! I did that for awhile but then had him fix it since wifey was complaining Not sure if that is what yours is, but sounds like it.

[Jeremy airjer W]

Put in a real heavy fuse and noticed the battery voltage guage would dip way down when I used turn signal and squealing would start.

[ccarlson]

Thanks for the tips. I'll start with these.

Box - mine is the opposite problem it sounds like, Mine squeals when I use the AC/defrost. I'll still use that as an option to check though. I first thought it was something to do with the AC/defrost components going bad. Still might be.

Airjer - I will try the di-electric trick and report back. I assume a little on each side of the belt since it uses both surfaces at different wheel's? I'm thinking the slight wobble I see in the belt between the tensioner and the alternator could be the issue since as you say, just a little loose play in the tensioner wheel might cause a little belt slippage on the alternator wheel and therefore a loss of electric power when needed the most??

Thanks all.

ccarlson

[mnscruff]

sounds like a dry tensioner bearing