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A/C High/Low pressure switches by zap
Started on: 05-30-2013 07:35 AM
Replies: 11 (2193 views)
Last post by: Tom Slick on 07-19-2013 09:20 PM
zap
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Report this Post05-30-2013 07:35 AM Click Here to See the Profile for zapClick Here to Email zapSend a Private Message to zapEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hi Guys,

I had the A/C Compressor replaced on my 88GT but I have a question. What will happen if the High pressure switch and the low pressure switch on the compressor are reversed as to the location on the compressor?l

Currently the A/C runs cold and there are no leaks.

Please respond as quickly as possible as I'm picking up the car this afternoon from the A/C shop. The shop owner told me he put the new switches in the new compressor in the same locations as the one he took out but he feels the swithcs are reversed based on the color coding (Red?White)

Thank 's
Zap

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masospaghetti
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Report this Post05-30-2013 12:16 PM Click Here to See the Profile for masospaghettiClick Here to Email masospaghettiSend a Private Message to masospaghettiEdit/Delete MessageReply w/QuoteDirect Link to This Post
I believe the two switches are connected internally on the compressor and therefore it doesn't matter which one goes where. They both operate on the high pressure side of the system.

Quoted from this thread http://www.fiero.nl/forum/Forum2/HTML/117640.html (thanks to RWDPLZ):

Switch Functions

The low pressure cut-off switch is normally open. This can be tested by using a multimeter set to continuity mode. There should be no continuity between the large round metal body, and the contact on top of the switch. When pressures inside the compressor reach a certain point, the switch will close, and turn on the radiator fan. This is designed to increase airflow over the condenser, and lower the system pressure. The switch closes at approximately 280 psi.

The high-pressure cut-off switch is normally closed. This can be tested by using a multimeter set to continuity mode. There should be continuity between the large round metal body, and the contact on top of the switch. When pressures inside the compressor reach a certain point, the switch will open, turning off the compressor, disengaging the compressor clutch plate. The switch opens at approximately 425 psi, and closes at approximately 200 psi.

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Joseph Upson
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Report this Post05-30-2013 12:36 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by zap:
The shop owner told me he put the new switches in the new compressor in the same locations as the one he took out but he feels the swithcs are reversed based on the color coding (Red?White)

Thank 's
Zap


Sorry Zap, but unless this is being done on the side by a novice, or for free, that's scary. I'm not an A/C tech and have no formal training in refrigeration but I know diagnosing a simple open/close pressure switch is only an ohm meter and attention to detail away. Maybe I expect too much from professionals these days but I certainly don't think you should be the one researching to find the answer to a problem for someone else that is providing a service on a stock arrangement that you're paying them to perform.

Make sure you do a thorough function check before you pay and run it all the way home and for the next few days.
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RWDPLZ
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Report this Post05-30-2013 05:44 PM 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
It doesn't matter which holes the switches go into, they both get their pressure reference from the same part of the compressor.

Compressor teardown:

http://www.fiero.nl/forum/Forum2/HTML/124630.html

Note the holes in the back of the compressor casting



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sricka01
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Report this Post05-30-2013 09:16 PM Click Here to See the Profile for sricka01Send a Private Message to sricka01Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by zap:

Hi Guys,

I had the A/C Compressor replaced on my 88GT but I have a question. What will happen if the High pressure switch and the low pressure switch on the compressor are reversed as to the location on the compressor?l

Currently the A/C runs cold and there are no leaks.

Please respond as quickly as possible as I'm picking up the car this afternoon from the A/C shop. The shop owner told me he put the new switches in the new compressor in the same locations as the one he took out but he feels the swithcs are reversed based on the color coding (Red?White)

Thank 's
Zap


Please have your installer pay attention to the new switches and whether he grounded out the high pressure switch. For whatever reason, grounding out this switch will cause your radiator fan to run full time regardless of engine temp or if A/C is turned off. You don't want that. http://www.fiero.nl/forum/Forum2/HTML/128461.html
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RWDPLZ
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Report this Post05-30-2013 10:06 PM 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
The switches need to be grounded to work properly. If grounding the switches is causing the fan to run all the time, there's something wrong with the wiring, or the fan switch. If the high pressure cut-out switch isn't grounded, the system will never switch on, and won't cool.
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lemon87
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Report this Post05-30-2013 10:59 PM Click Here to See the Profile for lemon87Send a Private Message to lemon87Edit/Delete MessageReply w/QuoteDirect Link to This Post
What do these two switches in the compressor look like? I believe I only have one.
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RWDPLZ
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Report this Post05-31-2013 04:34 PM 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
 
quote
Originally posted by lemon87:

What do these two switches in the compressor look like? I believe I only have one.


They're the red and white things here:

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Marvin McInnis
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Report this Post06-01-2013 01:37 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by sricka01:

For whatever reason, grounding out this switch will cause your radiator fan to run full time regardless of engine temp or if A/C is turned off.



No.


 
quote
Originally posted by RWDPLZ:

The switches need to be grounded to work properly. If grounding the switches is causing the fan to run all the time, there's something wrong with the wiring, or the fan switch.



If the fan runs all the time, either you used the wrong switch or it's wired incorrectly. The compressor high-pressure cutoff switch is normally closed; the high-pressure fan switch is normally open.
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sricka01
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Report this Post06-01-2013 01:55 AM Click Here to See the Profile for sricka01Send a Private Message to sricka01Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Marvin McInnis:


If the fan runs all the time, either you used the wrong switch or it's wired incorrectly. The compressor high-pressure cutoff switch is normally closed; the high-pressure fan switch is normally open.


I apologize. My switches were wired backwards after all. The fan no longer runs after connecting it to the right switch. Thanks for the confirmation!
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Marvin McInnis
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Report this Post06-02-2013 01:37 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
No need to apologize. I'm glad you got it fixed.
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Tom Slick
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Report this Post07-19-2013 09:20 PM Click Here to See the Profile for Tom SlickClick Here to Email Tom SlickSend a Private Message to Tom SlickEdit/Delete MessageReply w/QuoteDirect Link to This Post
nvm...

[This message has been edited by Tom Slick (edited 07-20-2013).]

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