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88GT A/C compressor high and low pressure switches by Carrolles
Started on: 09-03-2013 11:00 AM
Replies: 8 (446 views)
Last post by: Marvin McInnis on 09-07-2013 01:42 AM
Carrolles
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Report this Post09-03-2013 11:00 AM Click Here to See the Profile for CarrollesClick Here to Email CarrollesSend a Private Message to CarrollesEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am converting my 88GT from R12 to R134A while I have the engine/cradle out of the car. The low pressure switch on the compressor (the white mushroom looking one) still works but the white plastic keeper shattered. I bought a new 2 pin switch to replace it per another write-up on the forum (thanks for the info).

One Forum posting discussed the fact that after installing one of these switches per the instructions (one wire connects to the harnes wire, the other wire goes to ground) the radiator fan runs all the time that the key is in the on or ACC position whether the A/C is on or off. It suggested that if the ground wire is not be connected on the switch the fan works properly.

Does this render the switch useless altogether? This switch is sometimes called the Low Pressure Cut-out Switch. What is the purpose of the switch? Does it simply turn the radiator fan on when the slystem comes up to pressure? My understanding is that the radiator fan will turn on whenever the A/C is switched on (possibly not when it is in defrost mode).

On my 85GT both the high pressure and the low pressure switches have 2 pins and are wired per the instructions (meaning the second wire is connected to ground). The radiator fan runs allt he time.

If I remove the ground wire connection the fan works properly but will the switch serve whatever other function it is intended to do?
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Phil
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Report this Post09-03-2013 11:55 AM Click Here to See the Profile for PhilClick Here to Email PhilSend a Private Message to PhilEdit/Delete MessageReply w/QuoteDirect Link to This Post
The high and low pressure switches on the A/C compressor control the compressor clutch.
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masospaghetti
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Report this Post09-03-2013 12:12 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
One of the switches is a safety cutoff for the clutch. The other controls the radiator fan as a backup AND to provide cooling when the a/c controls are set to defrost.

In defrost, the a/c head unit does not turn on the radiator fan, unlike the other control positions (presumably because in defrost maximum cooling isn't usually needed). If the refrigerant gets too hot, the switch will turn on the fan.
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Carrolles
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Report this Post09-03-2013 01:49 PM Click Here to See the Profile for CarrollesClick Here to Email CarrollesSend a Private Message to CarrollesEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the replies.

Any idea on the validity of the recommendation to not connect both ground wires to prevent the fan from running all the time?

One curious thing is that when the O'Reilly salesperson called up the Santech part number it crossed over to their switch which had a 25 psi set point. If my 85GT has this incorrect switch that would explain why the fan runs all the time. The correct low pressure switch closes at 283 psi and re-opens at 210 psi.

[This message has been edited by Carrolles (edited 09-03-2013).]

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Carrolles
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Report this Post09-05-2013 04:30 PM Click Here to See the Profile for CarrollesClick Here to Email CarrollesSend a Private Message to CarrollesEdit/Delete MessageReply w/QuoteDirect Link to This Post
TTT
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RWDPLZ
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Report this Post09-05-2013 06:24 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 Carrolles:

Thanks for the replies.

Any idea on the validity of the recommendation to not connect both ground wires to prevent the fan from running all the time?



Complete crap. It will only cause the fan to run all the time if you use the wrong switch, or there's a wiring problem.

Here are the switches:

http://www.fiero.nl/forum/Forum2/HTML/117640.html

The switch with the 25psi set point is probably the switch for the V5 compressor, used on 86-88 4 cylinder cars. Can't tell without the part numbers.
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hdryder
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Report this Post09-05-2013 09:27 PM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
Has anyone had to adjust the Clutch air gap on a new rebuilt compressor by 4 SEASONS, or another company?

Thanks for the help.
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Carrolles
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Report this Post09-07-2013 01:33 AM Click Here to See the Profile for CarrollesClick Here to Email CarrollesSend a Private Message to CarrollesEdit/Delete MessageReply w/QuoteDirect Link to This Post
Rwdplz
I used your post for reference when I bought the new low pressure switch. I installed it and connected the second wire to ground. I'm hoping the pressure setpoints are correct. There was a sticker on the switch listing the on and off setpoints as 20 and 15 kn which is around 430 psi. The original should be around 283 on and 200 off.
It just didn't sound right not connecting the ground. I was afraid the switch would not function at all that way.
Once I'm finished with the 88 I'll look at the switch on the 85. I'm hoping to find the wrong low pressure switch was installed.
Thanks for the input.
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Marvin McInnis
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Report this Post09-07-2013 01:42 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
For reference, both of the switches mounted on the DA6/HR6 compressor (as used on your V6) are high-pressure switches. The first switch is normally open, and it closes to turn on the radiator fan when the high-side pressure goes too high. The second switch is normally closed, and it opens to disengage the compressor clutch when the pressure goes even higher. The only low-pressure switch in a DA6/HR6 system is mounted in front, on the accumulator.

[This message has been edited by Marvin McInnis (edited 09-07-2013).]

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