Problems after converting to R134a

Hey guys,
I just had Ms. Roadie converted from R12 to R134a due to the fact that she was 1 pound low on R12 and the cost to put a pound in was a few buck cheaper than converting. Anyway. It appears that the compressor is short cycling now (even more frequently than when it was low on R12, like it stays on for 5 seconds then turns off for 5 seconds, then turns back on. . .the cycle never ends when the ac is on), and really bogs down the motor while idling/driving that I notice a difference performance wise.

I was reading over buickwagons A/C post on the other forum, which got me to wondering. . . do you think it's short cycling because the low pressure switch needs to be adjusted to have it kick off at a higher psi? I would hope it's not due to the system being low on freon considering I just had it converted yesterday.

The mechanic did mention that what he pulled out of my system was really black, and he had to clean his filters after evacuating my system.

I'm just hoping there wasn't any damage done to the compressor and such during this conversion.

It's low. Hope he used the correct oil, and a new accumulator. If there was black, he should have flushed, and replaced your orifice tube, too.

as jay said the orifice tube could be plugged,. if it,s full of black "stuff" the compressor is dying,.

why didn't you use the duracool 12a?

He did flush the system, and replaced the orifice tube, it's still using the original accumulator though. We discussed the issue over the phone and he explained that the low pressure switch is setup for an R12 system (30psi) and I would need to replace the low pressure switch, with one that works with R134a (21psi). I asked him if we could adjust the switch already in there, he stated he didn't think it couldn't be adjusted. I told him I did some searching on the way back machine and found that my switch can be adjusted. So. . .Today at 4:30pm (stupid job) we will be adjusting the low pressure switch to cut off the compressor at 21-22psi.

I figured converting to the R134a would be the cheaper option in the long run.

JMHO, of course, but... the accumulator should be changed.

Adjusted the low pressure switch and everything is working good/normally now. Time to invest in a set of gauges and a vacuum pump, so's I can do this stuff myself in the future.

One thing to think of - if you are buying junkyard compressors and putting them in, it's worth getting a good two-stage vacuum pump.

BUT - if you are buying a parts store compressor with a warranty, read the warranty very carefully as they will only honor a compressor warranty when certain conditions are met.

When I replaced the leaking compressor on my 9C1, I bought the compressor, dryer (accumulator), orifice tube, new Dorman compressor lines (my high side valve was leaking and the Dorman lines are slightly shorter which eliminates the control arm rubbing problem the stock lines had) and all o-rings directly from Advance. Since the system had already leaked out I replaced everything myself, then took it to a shop WITH THE OLD PARTS in hand and had them vacuum out and refill the system, and write down on the receipt that they inspected the old parts and there was no debris in them. I then kept that receipt and the Advance receipts as proof in case the compressor failed.

Because of this reason, I have not purchased a vacuum pump.

scoffman wrote:

I asked him if we could adjust the switch already in there, he stated he didn't think it couldn't be adjusted. I told him I did some searching on the way back machine and found that my switch can be adjusted. So. . .Today at 4:30pm (stupid job) we will be adjusting the low pressure switch to cut off the compressor at 21-22psi.

Tee hee hee. Gotta love it.

Jay's right though -- change the accumulator. For one thing, all the desiccant is in the accumulator. For another, the accumulator accumulates -- contaminants as well as refrigerant. If your system was full of black death, then your desiccant is done and your accumulator is a full of goo. If someone tried to flush the accumulator with anything other than refrigerant, then it is contaminated with the flush chemical(s).

As for the vacuum pump, a two stage pump will draw down a vacuum faster, but not necessarily lower. The single stage is fine for the shadetree mechanic who uses it only occasionally. The two stage is worth it for a shop that has to crank them through. Do not bother with one of those air-powered vacuum pumps though, they do not draw a low enough vacuum to properly boil the moisture out of the oil.

Leave the vacuum on the system for several hours if possible. Even at a near-perfect vacuum, it takes time for the moisture to boil out of the oil. Run the pump at least 30 minutes to start, then 5 - 10 minutes every 30 - 60 minutes thereafter, to remove the traces of moisture that boiled out since the last time you ran it and to maintain the vacuum (pressure will rise slightly as vapour accumulates). Signs that vapour is still present (or the system is leaking) include a slight mist from the pump exhaust and a sound like shaking some loose gravel in a tin can (vapour bubbles imploding in the pump oil).

Speaking of pump oil, make sure it's reasonably clean and fresh. The ability of the pump to draw an effective vacuum depends in part on having uncontaminated pump oil. Some even recommend changing the pump oil every use, but I think that's overkill. I change the oil if the pump has sat unused for a month or more, and that seems to be fine.