S70 1998 with 166k mi A/C stopped working

Second attempt to join group.
The A/C was working fine. Then I replaced the alternator and
installed a new cabin filter.
When the A/C stopped, I assumed I had pinched a wire installing
the ALT. Visual inspection dismissed the possibility. Neither
the A/C nor the Recirc Light light or flash. There are two
wires feeding into the inboard side of the compressor. With
all the requirements met (fan on, A/C button in, hot cabin,
knob set to maximum cooling) there is zero voltage input to
both of these wire to the compressor. Jumping the two pressure
switches on the refridgerant lines had no effect. Nothing
seem to make the clutch engage. This appears link a blown
fuse or fusible link, Please advise.
Do I need a Control Panel? Can a control panel be

 

Can you confirm that with the AC button pressed that the green light does
NOT come on?

If that is the case, then you have lost power to the switch for some reason-
initially check the multiplug at the rear of the HVAC controls. (I assume
you have manual AC , rather than climate??)

I can check and tell you which fuse the a/c is supplied from if you like.

The ECU has ultimate control of the compressor clutch and condensor fan, but
the green light should still come on.

Tim..

 

Tim,
Thanks for your reply. The Green Light does not come on ever(since AC
stopped) I have disconnected and reconnected the two multiplugs at
back of Control Panel. I do NOT have automatic climate control,
but have single switches for both A/C and Recirculation. Temp control
knobs are surrounded by red and blue "arrows". Fan is manually
controlled. I have checked the two fuses that seemed related,
- Climate diagnostics
- Fuse 31
I wish I had a pinout for the two multicables on the Multicable.
I think the CP must have gone bad. I hate to buy one before
I can check the expected voltage at the CP. I find plenty
of used CPs with automatic climate control, but none without
on Ebay.
Do I understand it correctly? If the fuse for the CP is good,
the light will come on. Is there anything else that could stop
power getting to the green light? I need a pinout to check for a ground
connection. Perhaps I can assume that a brown cable is ground.
I am finding no OBD II error codes.
There are two pressure sensors on the refridgerant lines that stop
the clutch engaging --- any other things that do this outside the ECU?

 

Thanks so much for your reply.
The green light on the A/C switch does not come on
when pushed in,ever . I have checked fuses, including #31 Climate
and one labelled "Climate diagnostics" #5? I have removed
and reseated the two multicables at the back of the Control
Panel. A/C is not automatic. There is a single button each
for the A/C and Recirc and the Temp Control buttons are surrounded
by red and blue "arrows". The Fan is manually set. I am
seeing plenty of CPs with automatic climate control
at Ebay, but none without. I think I need a pinout for the
two multicables to see what is arriving and what is leaving.
I hate to buy a CP without knowing for sure it is bad.
I can not do that without a pinout, as I see it. I have
a Haynes Manual , but it does not have an AC wiring map.

At the back of the Control Panel there are two multicable
connectors. My finding with car idling
Connector #1 Gray Body with six wires
Reading directly from connector wires,disconnected from CP
-----------------------------------
Volts
Blue/Orange 0
Blue/White 0
Blue 0

Grey/Green 0
Blue/Brown 0
Yellow/Purple 13.7

Connector #2 Green Body with 22 positions but 15 wires
There is a 12 position and a 10 position side
My finding with car key in position 2, not running.
Reading directly from connector wires,disconnected from CP
-----------------------------------
10 position side
Volts
1 - Gray 0.06
2 - Gray/orang 0.06
3 - Grey/Red 0.06
4 - Grey/Black 0.06
5 - Grey/White 0.06
middle break here
6 - Yellow/Purp 12.71
7 - 10 empty

12 position side
1 - Gray/Brown 0.04
2 - Brown/Orange 0.04
3 - Brown/Pink 0.03
4 - Brown/Green 0.03
5 - Brown/White 0.04
6 - Black (Grnd) 0.0
middle break here
7 - Red 12.4
8 - Pink 0.03
9 - empty
10 - empty
11 - empty
12 - Gray/Blue 0.006

 

http://pliki.volvo.techno.org.pl/vo...70coupe_1998_wiring_diagrams_section_3_39.pdf

 

Without looking at the wiring diags (its 3am!) i am fairly sure that the AC
switch takes power from the Fan switch- i.e. if the fan switch is in
position 1 or greater, then the ac switch gets power. I can let you know
which wire should have the ac signal on it when the switch is pressed. This
goes straight to the ecu. You may be lacking an earth at the CP which is
preventing the green light coming on, but this will not affect the ecu
engaging the compressor.

This is not as simple as it first appears.

There is a low pressure switch (on the central bulkhead- 2 wire) which will
open when the low side has insufficient pressure caused by a low charge- its
there to protect the compressor.

The second 3 wire sensor by the slam panel is a variable pressure transducer
which the ecu monitors to control the condensor fan, and compressor clutch
to balance what the evap temp sensor tells it.

There is also a super heat switch on the back of the compressor.

Hope this helps so far.

Tim..