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87 gt ac trouble by John MacDonald
Started on: 06-29-2013 01:41 PM
Replies: 8 (207 views)
Last post by: John MacDonald on 07-02-2013 10:03 PM
John MacDonald
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Report this Post06-29-2013 01:41 PM Click Here to See the Profile for John MacDonaldClick Here to Email John MacDonaldSend a Private Message to John MacDonaldEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hello, I am new to the forum and recently bought my first fiero.
I am having a hell of a time trying to trouble shoot my ac.
I have replaced the relay and charged the system. The compressor now turns on and works, but when the pressure reaches 48 psi the pressure drops to 25 psi within a second and shuts the compressor off.( so the compressor runs for 1 second every minute or so)
If I jump the compressor directly from the battery the pressure drops to 0 within 3 seconds.
Any and I do mean ANY help would be much appreciated.
Thanks,
John

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GreenPlatypus
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Report this Post06-29-2013 08:19 PM Click Here to See the Profile for GreenPlatypusClick Here to Email GreenPlatypusSend a Private Message to GreenPlatypusEdit/Delete MessageReply w/QuoteDirect Link to This Post
Are you using R134a or R12 or something else entirely? Which pressure, high or low? I assume it is the low side. Sounds like something is either plugged or restricted. When was the last time the a/c worked? Did you replace the orifice tube? How about the accumulator? Did you flush the lines, condenser, evaporator? Was the system properly evacuated, put under a vacuum and recharged? Know for sure it is a good compressor? This may be something you may have to take to a specialist for diagnosis. Doing the work is the easy part. Figuring out what is wrong, that is the fun part.
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ltlfrari
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Report this Post06-30-2013 12:14 AM Click Here to See the Profile for ltlfrariClick Here to visit ltlfrari's HomePageClick Here to Email ltlfrariSend a Private Message to ltlfrariEdit/Delete MessageReply w/QuoteDirect Link to This Post
It's supposed to cycle like that, that's normal. If you have cold air and no other issues it's fine.
There's loads of ac related info on here, just use search. Every summer a/c topics sprout like weeds LOL!

P.S. Welcome to the madness.

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Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

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[This message has been edited by ltlfrari (edited 06-30-2013).]

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RWDPLZ
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Report this Post06-30-2013 01:02 AM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
If it's cycling that quickly it sounds like the system is low on refrigerant. 25 psi cut-out is perfect for R-12 systems, but you'll want to adjust it down to 21 if you've converted to R-134A. R-12 capacity is 2.5lbs, R-134A is 80-90% of that, usually 3 12oz cans.

What are the static pressures and outside temperature, and the pressures when the car is on?
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John MacDonald
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Report this Post06-30-2013 01:00 PM Click Here to See the Profile for John MacDonaldClick Here to Email John MacDonaldSend a Private Message to John MacDonaldEdit/Delete MessageReply w/QuoteDirect Link to This Post
The system is 134a.
I did not flush the system. When I bought the car there was no belt on the compressor so I figured it was seized.
It turns out the compressor works fine.
I also had to replace a relay and that is working now.
I put 34 oz of 134 in the system.
I have been trying to use the gm service manual and a Haynes to trouble shoot it and here is what I have so far.
static pressure when car has been sitting is almost 100 psi (outside temp 75), The second I start the car and turn the ac on, the compressor starts and runs for 1/2 a second and drops the pressure to 25 and shuts off. It then takes a couple minutes to build back up to 55 or so and runs for 1/2 a second again instantly dropping pressure to 25 psi.
I jumped the compressor and it will take the pressure all the way to 0. This does give me cool air but It runs it down to 0 psi.
As I said before, I am at a complete lose here...
Thanks a ton for the responses, I feel like a complete moron here and im starting to get frustrated.
Love the site and thanks for the help.
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KY87fierogt
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Report this Post06-30-2013 02:57 PM Click Here to See the Profile for KY87fierogtClick Here to Email KY87fierogtSend a Private Message to KY87fierogtEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by ltlfrari:

It's supposed to cycle like that, that's normal. If you have cold air and no other issues it's fine.
There's loads of ac related info on here, just use search. Every summer a/c topics sprout like weeds LOL!

P.S. Welcome to the madness.


I agree! I have had the same issue on different vehicles(cycling on and off without cooling effectively). I would add a little more freon. Don't over do it.

Edit: after thinking about it a little,....you could have a overcharge situation. What is the high side reading when it cuts out? It will most likely cut out at 400-450. Did you add oil? (Adding oil to the system without purging it first would, I believe, reduce the amount of freon you could put into the system. Did you put a vacuum on the system prior to charging?

[This message has been edited by KY87fierogt (edited 07-01-2013).]

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Rodrv6
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Report this Post06-30-2013 03:43 PM Click Here to See the Profile for Rodrv6Click Here to Email Rodrv6Send a Private Message to Rodrv6Edit/Delete MessageReply w/QuoteDirect Link to This Post
Sounds like a plugged orifice tube. What does the high side pressure do?

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Rod Schneider, Ball Ground, Ga.
"You can't have too many toys!"
1988 Fiero GT
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ltlfrari
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Report this Post07-01-2013 08:25 AM Click Here to See the Profile for ltlfrariClick Here to visit ltlfrari's HomePageClick Here to Email ltlfrariSend a Private Message to ltlfrariEdit/Delete MessageReply w/QuoteDirect Link to This Post
It does sound like the orifice tube is blocked. With a full charge it should not drop to 25 psi so quickly and you should not be able to get it to go to 0 psi. Sounds to me like once the compressor turns off the pressure is mainly equalizing back through the compressor.
If you get it to 0 psi and then turn off the engine, can you hear a hissing from the orifice tube area. That's the pressure equalizing through the tube once the vacuum is removed. If not then that would again indicate a blocked tube.
Only way to really tell is to pull the orifice tube and take a look at it.

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Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

www.ltlfrari.com

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John MacDonald
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Report this Post07-02-2013 10:03 PM Click Here to See the Profile for John MacDonaldClick Here to Email John MacDonaldSend a Private Message to John MacDonaldEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks guys. I will see if I can check it out this weekend.
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