Automotive Air Conditioning Information Forum (Archives)

Edfiero on Tue August 05, 2014 9:34 AM

Year: 1984
Make: Pontiac
Model: Fiero
Engine Size: 2.5
Refrigerant Type: 134a

I've had my 84 Fiero converted to 134a and I'm not happy. I wonder if I have a problem, or if my experience is something 'normal' with a conversion.

I replaced the compressor with an HR6 from Autozone, changed the oil, the O rings, Orifice tube, Accumulator, and pulled a vacumn before refilling with 2lbs of 134a.
The A/C is nice and cold. However my problem is related to the cycling of the compressor.

1. At highway speeds, (engine running 3000+RPM) whenever the compressor cycles on, I can feel a noticable 'drag' on the engine. Granted the car has only 90hp on a good day, I don't remember such a hit back in the R12 days. Also the belt 'chirps' on the compressor when it cycles on. This is a new Gates belt, pulled very tight. Also I scuffed the pulley grove to ruff it up, to minimize the belt slipage.

2. My other concern/question relates to the cycling itself. How much time should I expect the compressor to be disenaged during each cycle? When it disengages, it is 'off' for only about 3 seconds before it comes back on. Then after 'on' for 20 seconds or so it cycles off again. So I'm seeing 3 complete cycles a minute. This combined with my issue #1 above, makes for a jerky/annoying ride. 3 cycles a minute may be normal, but in any other car, the belt chirps and engine drag isn't there so the cycling is not noticable.

At slow speed/low RPM, the compressor doesn't cycle very often so the problem isn't noticable then.

Thoughts?

wptski on Tue August 05, 2014 9:54 AM

The capacity chart at this site show the 86-88 Fiero, all engines on R12 as 40oz. Conversion to R134A, they say start at 90% of R12 capacity so you are a bit undercharged which may be part of your problem.

Edited: Tue August 05, 2014 at 9:55 AM by wptski

webbch on Tue August 05, 2014 1:32 PM

Was the compressor replaced due to problems, or just because you were converting? Just want to make sure the old one didn't die and leave it's guts behind to destroy the new compressor. Were the lines flushed of the old oil then, or did you just dump out what you could?

I'd get a set of gauges on it to see if the compressor is actually under heavy load. Assuming you put in the correct quantity of compressor oil, that ought to rule out lubrication issues I'd think...especially if you're within about 4 oz of recommended charge level.

Dougflas on Tue August 05, 2014 1:37 PM

As stated, you're slightly low on refrigerant. Take a temp reading on the input and output lines of the evaporator. The output should be a few degrees colder than the input. GM used to stae when adding refrigerant to a partially charged system, after the evap lines are equal temps, add 2 oz of regrigerant.

Edfiero on Tue August 05, 2014 8:49 PM

Quote
Originally posted by: webbch
Was the compressor replaced due to problems, or just because you were converting? Just want to make sure the old one didn't die and leave it's guts behind to destroy the new compressor. Were the lines flushed of the old oil then, or did you just dump out what you could?



I'd get a set of gauges on it to see if the compressor is actually under heavy load. Assuming you put in the correct quantity of compressor oil, that ought to rule out lubrication issues I'd think...especially if you're within about 4 oz of recommended charge level.

The old system worked fine, there was NO trash in the Orfice when it was replaced. The only issue is it was constantly leaking. Ran the leak detector on several times and couldnt find a leak, but every spring I would find it was completely out of Freon. Got tired of paying for a recharge, so bit the bullet and did the conversion.

Yes new oil was added at time of conversion.

Edfiero on Tue August 05, 2014 9:02 PM

Quote
Originally posted by: wptski
The capacity chart at this site show the 86-88 Fiero, all engines on R12 as 40oz. Conversion to R134A, they say start at 90% of R12 capacity so you are a bit undercharged which may be part of your problem.

I don't disagree it could probably take a couple more ounces, but I don't see how that would help with my problem. Wouldn't adding more only raise the pressure, causing the compressor to be even harder to turn, making the problem even worse?

Air temp at the vent is around 40 degrees, so cooling doesn't seem to be a problem.

TRB on Tue August 05, 2014 10:38 PM

What are the pressure readings?

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HECAT on Wed August 06, 2014 7:05 AM

Is it cycling on high pressure or low pressure? Lugging the compressor makes me think high pressure. Low charge is what some other comments have indicated. "Changed the oil" and "recharge every spring" makes me think the compressor may be trying to compress too much oil. Did the system get flushed clean and dry before installing new compressor? Was the new compressor drained? How much fresh oil was added?

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