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2002 Bonneville SLE 170,000 miles.

I have noticed that when I idle with my A/C running, specifically when the compressor clutch kicks in, I lose oil pressure (just below 40) AND my battery gauge moves down briefly. It seems as if the clutch is sticking and causing the belt to stop for a minute, thus not running the altenators, oil pump, etc. Also when the A/C is on and idling there is a terrible rattling sound. None of these symptoms exist when the A/C is off.

Should I look into replacing the A/C clutch, or have you guys had similar problems and it was something else? I think it has to be something that is belt powered that is causing the brief loss of power.

Toyfare wrote:2002 Bonneville SLE 170,000 miles.

I have noticed that when I idle with my A/C running, specifically when the compressor clutch kicks in, I lose oil pressure (just below 40) AND my battery gauge moves down briefly. It seems as if the clutch is sticking and causing the belt to stop for a minute, thus not running the altenators, oil pump, etc.

Always hoping for the simplest explanation for a problem, I'd suggest to check the wear on your belt. Look at the marks ont he tensior pulley hub. The belt should be on the middle mark. Mine is at the mark for the longest the belt can stretch/wear to. That means there's less tension on the belt against the pulleys for the AC, Power Steering, alternator, so it is more likely to slip. My belt makes a squawking sound when it slips at the AC. It's a replacement belt and is the soft surface type by Dayco. Was around $40 $45.

The tensioner at 170,000 and 11 years may have lost some tension in the spring besides the belt having lengthened. On my car at 160,000 mi, I'm considering replacing the tensioner when I take it off to replace the plastic elbows for the heater coolant.

Also some contaminant may have gotten on the belt such as coolant if you had a leak or blown hose? Also something from the road? I get a squawk after driving through water puddles at 30 mph because the splashed water ends up on the lower engine and belt.

You can try spraying water on the belt while it's moving from a hose to see if that affects the noise you're getting and determine that it is the belt.

The oil pump is internal: it's not run by the belt. If the engine slows with the load of the AC and the electrical load for the clutch magnet, that may drop your oil pressure due to wear normal in the engine at 170K.

You can try loading up the alternator with rear window and running a power window up and down along with the blower motor on high and see if that aggravates the slipping at the alternator pulley.

Happens to my car sometimes too, and when I turn the AC off. The voltage gauge will drop for a couple of seconds and slowly build back up. A quick rev will bring back up to normal too. This has been happening to my car for probably 2-3 years now.

I checked out the noise from under the hood this morning. The A/C clutch is off balance while the air conditioning is running. That is what makes the terrible rattling noise. The belt looks in good condition (no cracks) and I hear no other noises coming from other pulleys. When I turn off the A/C the clutches disengages and the noise/wobbling stops. Should I attempt to fix the A/C clutch or will it be OK out of balance?

Anything rotating an out of balance on anything will lead to further issues. It will probably cause the shaft seals to go bad and leak out the coolant. You could try to repair it yourself or put in a new compressor. I have never worked on the clutches or compressors, but some here have.

Just remember if you replace the compressor yourself, you will need to have someone evacuate the coolant before removing it.