Flapping AC Belt when AC on?

[MPDano]

Now that I figured out my Heat issue, now it's time to move on to my AC.

When I turn my AC on, I can hear the belt flapping against the Oil Pan (so it's looks like). I also get a short squeal when I turn on the AC. I am pretty sure my belt tension is correct, but will check again when I get home.

Rjm65 and I Evac'd the System of R12 a couple months back and I fitted it with an R134 Kit and filled it up with that R134/Oil Cans to Spec. I believe it was 32 ounces.

I am getting cold air now inside the car

Can a bad compressor or low oil be the problem? Or something else?

[psychII]

fix one thing and another pops up.

maybe the compressor is seizing? Did you pull the compressor and put oil in it? I'm not sure if that will help, but when I did my AC, I pulled it and put about 4 or 6 oz in.

[dr bob]

Check the belt tension. You should be able to get one belt-thickness of deflection at the middle of the span with firm thumb pressure. No more. Inspect the belt that's on there, and replace if the drive surfaces (the sides of the V) are polished/glazed or if you see any cracks. If this one is bad it's not a bad idea to just replace all of them at the same time. New belts get a bit more initial tension, then a retension after some driving stretches/wears them just a little.

Most belts, especially the flat ribbed alternator belt on the later cars, tend to be under-tensioned by less experienced owners or technicians. IIRC the factory WSM gives a proper reading if you happen to be using the Porsche tension gauge, but meanwhile the popular Kempf tool is not adapted well for this with just one tension window supplied. The rule-of-thumb method above applies to the ribbed belt too.

[MPDano]

Originally Posted by dr bob

Check the belt tension. You should be able to get one belt-thickness of deflection at the middle of the span with firm thumb pressure. No more. Inspect the belt that's on there, and replace if the drive surfaces (the sides of the V) are polished/glazed or if you see any cracks. If this one is bad it's not a bad idea to just replace all of them at the same time. New belts get a bit more initial tension, then a retension after some driving stretches/wears them just a little.

Most belts, especially the flat ribbed alternator belt on the later cars, tend to be under-tensioned by less experienced owners or technicians. IIRC the factory WSM gives a proper reading if you happen to be using the Porsche tension gauge, but meanwhile the popular Kempf tool is not adapted well for this with just one tension window supplied. The rule-of-thumb method above applies to the ribbed belt too.

I will try this "one belt thickness" method when i get home. Belt is new as is ALL my belts when i put this engine in this year. Pretty sure it's still good to go.

If tension is good, then I will add more oil as psychII states.

Will report back.

[MPDano]

I checked the tension as Dr Bob explained and it's right on. It's "one belt thick" as you push down on it. I will try adding a little bit of oil and see if that helps it.

[MPDano]

Ok, it finally cooled off just before dark. Friggin 101 here in El Cajon. Anyways, decided to recheck tension and it did feel like I could tighten it up a little bit more. I went and tried the AC again, no more flapping. I had it running for a good 10 minutes when I started to hear a humming noise. I could see the belt starting to slightly flap enough to make it hum. Revved it up to 3K for a minute and back down, hum still there. I guess I will try to put oil as I said before and see if that cures it.

[MPDano]

Ok, saw this chart on Oils to use. Which type is the correct one to use in our compressors? And how much?

Recommended Lubricants for R-134a Import Compressors:

* Behr/Bosch rotary compressors - Ester 100;
* Behr/Bosch piston compressors - PAG 46;
* Calsonic V5 - PAG 150;
* Calsonic V6 - PAG 46;
* Diesel/Kiki (Zexel) DKS, DKV & DCW - PAG 46;
* Hitachi (all) - PAG 46;
* Keihin (all) - PAG 46;
* Matsu****a (all) - Ester 100;
* Mitsubishi FX80 - PAG 100;
* Mitsubishi FX105 - PAG 46;
* Nihon (all) - Ester 100;
* Nippondenso 6P, 10P, 10PA, 10P08E - PAG 46;
* Nippondenso SP127, SP134 and 6E171 - PAG 46;
* Nippondenso TV series - PAG 125;
* Panasonic (all) - PAG 46;
* Sanden SD500 and SD700 - PAG 100;
* Sanden SD710, SDB, TV and TRS - PAG 46; and
* Seik-Seiki (all) - Ester 100.

[dr bob]

The compressor is lubricated by an oil mist carried by the refrigerant. While there's a possibilty that you are in fact low on oil, there's a simialr possibility that adding oil wil do more damage than good if you add too much. Also interested in how you add oil to a chantged system, especially if you still have R-12.

Refrigeration systems will in fact have some compressor vibration at low RPM's as a normal condition. The belt does absorb the uneven load from the compressor as it relates to th uneven idle speed of the engine.

My point is that you should see how it operates at normal (>1500) RPM's before you decide you have a problem. If the compressor was low enough on oil to have a valve stuck open or a piston coming apart, adding oil now won't do anything beyond giving yourself more oil to flush out of the condenser loop.

[MPDano]

Hi Dr Bob,

Rjm65 and I evacuated the system of R12 before fitting the R134 Kit. I do remember charging the system with that R134 Freon/Oil Mix with the amount in specs. Maybe you need more oil that what is in those mix cans?

So by your reply, our compressors are Piston. Behr/Bosch? If so, Ester 100 is the proper oil. Correct?

[Dozman]

If you do not correctly flush out the low side, high side lines or not completely flush out the condensor or not replace the receiver drier, oil that is entrained in refrigearnt can be laden in these areas after evacuation of refrigerant. Thus, if oil is here and you add oil you might over fill the oil capacity. Which is detrimental to the a/c system.

[MPDano]

Can anyone answer what oil to use? Ester 100? Or ???

[neil30076]

My 81 had a Nippondenso originally, and thats what i replaced it with, so presumably PAG 46, i haven't got that far yet, though :-)

[MPDano]

Hmm, Nippondenso can't be original to the car, is it? I guess I should go out there and see if there are marks on the compressor just to be sure.

[neil30076]

My mistake, yes, a bosch came out and nippo went back in, they are form fit and function identical. Manufacturers plate is on end of pump, so its not easy to see !

[MPDano]

Ok, climbed under my car and wrote all that was there.

Bosch
Made in Japan
0 140 904 507
ETB 12V Oil 280CC

Now, is this Piston or Rotary?

[dr bob]

I used the Ester oil when I did my R-134a conversion. Mine is N-D compressor in the later car. The polyolester oil has the advantage of compaitibility with both R-12 and R-134a.

Use a stethoscope to see if the rumbling/humming is coming from the compressor, and see if it's rod knok or piston slap (too-late indication of running with low oil) or a bearing noise. The nature of the noise may help you decide a repair path. Bearing can be replaced, although finding a seal kit for that Bosch compressor isn't as simple as it is for the N-D units. If it is metal parts slapping inside from low oil, you'll want to replace the compressor as a unit before it grenades and contaminates a bunch of stuff.


----
When doing a conversion, it's pretty important to get as much of the old oil out as possible. The mineral oil used in the R-12 systems turns to jelly in R-134a, and particularly when PAG oil is ued in the conversion. It truly escapes me why most popular consumer-level "conversion kits" have PAG oil in them, but they do. Anyway, the oil as jelly does tend to interfere with the expansion valve, and can cause issues in the compressor if valves or oil passages are even partially blocked. Most of the oil in the system seems to reside in the drier and the compressor, so replacement of the drier is mandatory. Drain/flush/fill the compressor with polyolester oil as part of the reseal and re-hose effort during the conversion process. There will still be traces of the old oil in the evaporator, but usually not eough to worry about. A real system flush removes all doubt of course, but doing a good flush is generally beyond DIY capabilities.

[MPDano]

Too late, grenaded it last night. Put some Pag 46, 4 oz can. AC was feeling mighty nice and cold. I could hear the flapping coming back again, so I decided to take it for a drive and see if I can get it colder. Just left the driveway and smoked it. Turned AC off and looked under hood and the Clutch looks like it exploded. I can see melted plastic around the clutch area. It was dark out so I just drove it around the block and parked it. Compressor still turns so at least I didn't seize it and break something else.

I believe this means I need another Compressor and Drier. Whats a good replacement brand and less expensive?

Pics to follow.

[neil30076]

You can have the bosch i took out of mine - maybe make a good one out of 2, and mine may actually not be defective at all.
LMK

[MPDano]

Originally Posted by neil30076

You can have the bosch i took out of mine - maybe make a good one out of 2, and mine may actually not be defective at all.
LMK

I will totally take you up on that offer. Maybe this weekend pick up? Got wifes BDay Party on Sunday but I can probably sneak out and bring with Raymond (rjm65) with me. I am free Sat too.

[neil30076]

it's yours, email sent with my phone number, etc.