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A/C compressor control

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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greg850r
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A/C compressor control

Post by greg850r » Wed Jul 10, 2019 10:22 am

I have a 96 850T and I can't get the compressor to kick on. I tested it with a jumper wire and it does work. I jumped the high pressure switch to no avail. Rather than figure out which wires to jump on the low side (because there are 3) I just changed out the switch with a known good one.

I vacuumed the system down and it held 29 inches of vacuum for half an hour, then added one can of freon. I usually fire it up at this point and turn on high defrost to suck the 2nd can in. The blower in the car runs, but there is no compressor engagement. The climate control is giving me the 20 second flashing lights indicating a fault. Is there by chance a relay next to the fuse box I should look at? Pulling the A/C fuse (31) kills the blower and it runs again when I re-insert the fuse.


05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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abscate
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Re: A/C compressor control

Post by abscate » Wed Jul 10, 2019 10:47 am

One can should be enough to close the low pressure switch and cycle the compressor. Something is fishy in Sweden.


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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW

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greg850r
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Re: A/C compressor control

Post by greg850r » Wed Jul 10, 2019 12:18 pm

I know, right? I'm starting to suspect the little solid state thing on top the compressor. I hope not because that will mean a compressor change.


05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

Ozark Lee
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Re: A/C compressor control

Post by Ozark Lee » Wed Jul 10, 2019 1:13 pm

Some of the compressors have a thermal limit switch in series with the control line to the compressor. It is not mission critical and it can be bypassed as most of them have been since they are problematic.

That may be a simple solution.

...Lee


'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

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Re: A/C compressor control

Post by greg850r » Wed Jul 10, 2019 1:22 pm

Is the thermal limit switch the little box on top the compressor?


05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

Ozark Lee
MVS Moderator
Posts: 14793
Joined: Thu Sep 07, 2006 8:24 am
Year and Model: Many Volvos
Location: USA Midwest
Has thanked: 4 times
Been thanked: 45 times
United States of America
Ozark Lee

Re: A/C compressor control

Post by Ozark Lee » Wed Jul 10, 2019 1:55 pm

If it has a wire in and a wire out then yes. There were a couple of different styles.

...Lee


'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

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abscate
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Posts: 18194
Joined: Sun Feb 17, 2013 5:54 pm
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Trinidad & Tobago
abscate

Re: A/C compressor control

Post by abscate » Wed Jul 10, 2019 1:55 pm

You can test that by just putting 12V on the compressor directly.

Two cans will be 680g charge, pretty close to the 750gram fill spec.

The limit switch is in series with the 12V wire going to the clutch - Ive seen many types on Volvos so its best to follow the wires.

i have dilsiked wasps and Hornets since I got 36 Hornet stings on a 3 story ladder painting a barn in college.


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW

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Re: A/C compressor control

Post by greg850r » Wed Jul 10, 2019 3:37 pm

comp pic.jpg
Here's the type I have. I don't think bypassing the box as indicated will solve anything as it works wired to power now.
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05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

User avatar
abscate
MVS Moderator
Posts: 18194
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 200 times
Been thanked: 647 times
Trinidad & Tobago
abscate

Re: A/C compressor control

Post by abscate » Wed Jul 10, 2019 3:49 pm

You haven’t put a tune or swapped ECMs on this have you? There are issues between non stock software and AC


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW

User avatar
greg850r
Posts: 206
Joined: Thu May 03, 2012 5:06 pm
Year and Model: a long list
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Re: A/C compressor control

Post by greg850r » Wed Jul 10, 2019 4:05 pm

No, this is a one owner I bought with a burnt valve. I have not learned the whole custom tune thing yet. I do have a 97R someone swapped a 5 spd in and there's no trans control in it anymore. I need to find out if it is running the original ECM and what to do about it. That's next :)

I'm on a mission to get all these lingering projects done this year if you haven't guessed. :lol:


05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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