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98 S70 A/C clutch engagement

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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McKennaR
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Year and Model: S70 Base, 1998
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98 S70 A/C clutch engagement

Post by McKennaR » Tue Sep 18, 2012 12:36 pm

Preface:
I've been lurking around the forums for the better part of this morning researching, testing, failing, and researching again trying to troubleshoot the A/C in the S70. The car is a 1998 S70 Base n/a with 280,XXX and likely the original A/C compressor. I don't know when the last time the A/C worked. I extracted the car from a field in front of my Parent's house last November. It had been there for a few years, so I'd imagine it has been more than a few years since the A/C worked.

I'm fully aware of the fact that there's a higher than average chance that the system has moisture in it and is thusly trashed, but I need to get a baseline and figure out what exactly is gone before I start throwing parts at it. I can only assume it needs an evap, receiver/drier, etc.

I figured the compressor was a logical place to start. My methodology is that I'm going to feed the system some dye-laced refrigerant and run it for a week or so before going further... but in order to feed it some refrigerant, the compressor needs to work.

I can turn the center-portion of the compressor pulley by hand (with the engine off, naturally). It turns freely and isn't stuck. This leads me to believe A: there's zero pressure in the system and B: the compressor itself isn't seized.

Anyways,

Conditions:
Ambient temp of 73f, vehicle running, manual climate control switched to blower setting 4, A/C button depressed (green light on button illuminated), recirc depressed and illuminated.

I've tried in sequence:

1. Jumping the leads on the AC line that goes to the firewall.
-Results: This was the first thing I did, and I heard a "click" (louder than a relay) but no compressor engagement the first time I turned the A/C on via the switch inside. Subsequent attempts resulted in no more noises. As of this writing, it is noise-free.

2. Thinking the above might have hosed a relay or a fuse, I went through all of the fuses and relays associated with the A/C system. All good.
-Results: no change.

3. Reading about broomstick and bread-clip methods, I tried the former. If that worked, I was going to try the latter.
-Results: One chipped up broomstick handle but no compressor engagement.

4. With the switch illuminated on the MCC panel inside the car and the lead mentioned in # 1 jumpered, I'm receiving voltage to the bullet connector on the back of the compressor, in-line with the thermal switch and clutch. With the compressor still in the car, I can't snake my hands up and around to see if the clutch is receiving power.

5. One thing I noticed recurring in the threads on this topic throughout the internets, is that many posters indicate their engine fan relay would click and their engine fan would operate the instant the A/C button was pressed with the vehicle running. This does NOT occur on my car, though the engine fan works flawlessly when the temp-switch tells it to do so.

I'm at the stage where the next logical thing to do would be to snip the wires and bypass the thermal switch on the compressor to see if this completes the circuit.

Before I go hacking at wires, is there anything I've overlooked or perhaps something at which I should look closer?

Thanks

Ryan


Current: 89 745 turbo, 98 S70 Base 300k mi, 98 4Runner 351k mi.

jimmy57
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Re: 98 S70 A/C clutch engagement

Post by jimmy57 » Tue Sep 18, 2012 1:38 pm

Get a can of refrigerant and add some. The a/c high pressure sensor that signals the engine computer (ECM) about pressure for its control of the fan also inhibits compressor when the pressure is very low. When you get a 1/2 pound or so in it then the jumper at low pressure cycling switch will make it run without the rapid on-off cycling until it has closer to the right amount in it.



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kcodyjr
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Re: 98 S70 A/C clutch engagement

Post by kcodyjr » Tue Sep 18, 2012 1:49 pm

Not sure if it's still there in the S70, but my 850 has a dangling lead up near the fuse box that, when jumpered to (hot? ground? don't remember) will force the compressor to turn on.


1997 850 GLT sedan, 152K and WHOOHOO!
RIP 1996 850 wagon, 201K, hit by a runaway 4-wheeler
RIP 1996 850 GLT sedan 5spd, 260K, rearended someone
RIP 1986 245 boring, 200K, rusted beyond inspectability
RIP 1981 242 turbo 5spd, 300K, serious teenage crash

McKennaR
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Year and Model: S70 Base, 1998
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Re: 98 S70 A/C clutch engagement

Post by McKennaR » Tue Sep 18, 2012 2:11 pm

jimmy57 wrote:Get a can of refrigerant and add some. The a/c high pressure sensor that signals the engine computer (ECM) about pressure for its control of the fan also inhibits compressor when the pressure is very low. When you get a 1/2 pound or so in it then the jumper at low pressure cycling switch will make it run without the rapid on-off cycling until it has closer to the right amount in it.
I'd be happy to get any cycling at this point.

I was under the impression that that jumper up near the firewall would force the compressor on, regardless of what any of the other sensors or switches were saying?

I'll hit the auto place down the street and grab a few cans and see what happens.


Current: 89 745 turbo, 98 S70 Base 300k mi, 98 4Runner 351k mi.

jimmy57
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Re: 98 S70 A/C clutch engagement

Post by jimmy57 » Tue Sep 18, 2012 2:30 pm

On models w/o high pressure that is true but with that sensor in place the ECM can control compressor. Prior to 98 the pressure cycling switch could be jumped to battery but with 98's that switch is a signal to ECM and not in the circuit for clutch coil power.



McKennaR
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Joined: Sat Dec 31, 2011 4:09 pm
Year and Model: S70 Base, 1998
Location: XNA
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Re: 98 S70 A/C clutch engagement

Post by McKennaR » Tue Sep 18, 2012 3:12 pm

Cool, appreciate the info. Went to AutoZone and picked up a can of UV leak detector which turned out to be a waste of time (the UV part, not the refrigerant part)...

No sooner had the refrigerant started to flow than I heard a hissing noise from the condenser. Turns out buried between some bent fins was a decent sized hole.

So... anyone have a condenser (and while I'm at it, an accumulator) they'd be willing to part with?


Current: 89 745 turbo, 98 S70 Base 300k mi, 98 4Runner 351k mi.

Ozark Lee
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Re: 98 S70 A/C clutch engagement

Post by Ozark Lee » Tue Sep 18, 2012 3:17 pm

kcodyjr wrote:Not sure if it's still there in the S70, but my 850 has a dangling lead up near the fuse box that, when jumpered to (hot? ground? don't remember) will force the compressor to turn on.
That is the service starter lead. It is a convenient way to start the car from under the hood. The service starter lead is activated by jumpering it to + battery voltage. It is a great way to diagnose no crank situations since the only thing it sees on the way to the starter solenoid is the PNP switch - it bypasses the ignition switch and the immobilizer.

...Lee


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

jimmy57
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Re: 98 S70 A/C clutch engagement

Post by jimmy57 » Tue Sep 18, 2012 4:49 pm

If you look around you'll find new, no question it's good condensers for $100.
Accumulators can be had for $30.



McKennaR
Posts: 44
Joined: Sat Dec 31, 2011 4:09 pm
Year and Model: S70 Base, 1998
Location: XNA
United States of America

Re: 98 S70 A/C clutch engagement

Post by McKennaR » Tue Sep 18, 2012 5:59 pm

Roger that. I'm ordering a metric s**t ton of A/C stuff from some forum sponsors tomorrow afternoon for the Volvo. This just puts a boot in my behind to finish the 20g, AVO TMIC and Inlet hose install on my Legacy GT M/T car this week to free up garage space. I have a feeling being a winter beater in Maine for 280,000 miles is going to equal good times with the P'Blaster and a breaker bar.

I appreciate the info, as always, MVS & the forum contributors have saved me a decent chunk of change.

Thanks.


Current: 89 745 turbo, 98 S70 Base 300k mi, 98 4Runner 351k mi.

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