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AC pressure specs?

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, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Red-Arrow
Posts: 449
Joined: 26 Aug 2010, 01:07
Year and Model: 850 T5 1995
Location: Scotland.

AC pressure specs?

Post by Red-Arrow »

Hi guys, does anybody know the correct pressure setting for the AC on the 850?

I was thinking about buying a gauge set from Ebay with hoses and all but what good are they if I don't know the specs right.

Does Pepboys check the AC pressure for free? No I don't want to use them but I don't want to buy AC gauges just for one job.
Life would be enjoyable if it wasn't so painful to live.

jblackburn
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Year and Model: 1998 S70 T5
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Post by jblackburn »

It's dependent on the ambient temperature. The readings are on the back side of a can of R-134. I always aim for the low end of the values they show there. I try to fill the system when it's cooler out just so you make sure that it's got enough of a charge to keep the compressor from cycling in and out when the pressure is lower.
'98 S70 T5
2016 Chevy Cruze Premier


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

C@lvin
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Post by C@lvin »

There is no high side port on these cars to connect a gauge to. I picked up a single gauge for the low side port at Harbor Freight for around $10 but rarely use it. When the system gets low and stops cooling or the compressor starts cycling too much, I put in a can and it will start cooling again, sometimes but no very often it will take two cans. I've had my S70 (202K) for three years and each summer I have had to put in a can about April/May, another about July, and another in September. The can drains better if it's warm but be careful not to get it too hot (boom! :o ). Some people suggest putting it in warm water before hooking it up.
Calvin
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jblackburn
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Posts: 14050
Joined: 08 Jun 2008, 15:54
Year and Model: 1998 S70 T5
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Post by jblackburn »

I had to fill mine about every month last year...very annoying.

I put a can of this stuff in my S70 in April, and haven't had to fill it since!
'98 S70 T5
2016 Chevy Cruze Premier


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

Red-Arrow
Posts: 449
Joined: 26 Aug 2010, 01:07
Year and Model: 850 T5 1995
Location: Scotland.

Post by Red-Arrow »

I read that the only way to measure the AC system is by weight of freon?

I only have an Autozone and Pepboys locally. Would they sell the AC gauge? Should I just buy a can of the Gas with a gauge on it?
Life would be enjoyable if it wasn't so painful to live.

jblackburn
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Posts: 14050
Joined: 08 Jun 2008, 15:54
Year and Model: 1998 S70 T5
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Post by jblackburn »

They should sell both. Several cans of the stuff have a gauge attached like mine - that's ultimately the cheapest option as you can buy just replacement cans after the fact.
'98 S70 T5
2016 Chevy Cruze Premier


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

rsavin
Posts: 11
Joined: 11 Oct 2010, 15:21
Year and Model: 1994 850 Sed
Location: Canton, Michigan

Post by rsavin »

A 94 850 Sed, Manual AC. Typing on a phone. Akward at best.
I have a good basic knowledge of how ac works. My compressor was cycling often with slight cooling indicating low freon. I connected to the low side but had trouble getting the connector to snap on, loosing freon each attempt. Finally it snapped on and read 20psi but the compressor stopped and will not run. The dash light comes on at the switch that's it. Is 20 psi too low for it to start. No AC work done in 17 yrs. It sat for a year and the low freon was due to just time and dried seals I think. Seem odd that it would suddenly stop just ike that. Ideas anybody?

jblackburn
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Posts: 14050
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Post by jblackburn »

Yes - 20 psi static pressure is too low for it to cycle on.

Jumper the pressure switch at the back of the engine compartment, which will let the compressor run to take in refrigerant. Make sure to add it quickly, and once you get above 25 psi remove the jumper and re-connect the switch so the compressor won't burn up. Then just add it normally.

Image

You're going to need another can to fill that up if it's that low.
'98 S70 T5
2016 Chevy Cruze Premier


A learning experience is one of those things that says, "You know that thing you just did? Don't do that."

mercuic: Long live the tractor motor!

rsavin
Posts: 11
Joined: 11 Oct 2010, 15:21
Year and Model: 1994 850 Sed
Location: Canton, Michigan

Post by rsavin »

Thanks very much for your info and esp the pic, helps a lot. Just getting back to this post, too busy these days. Have not done the refill yet but no worries, sure it will go smoooth. Thanks again, this is the best site out there,barr none! Heading to the donate page...Cheers.

rsavin
Posts: 11
Joined: 11 Oct 2010, 15:21
Year and Model: 1994 850 Sed
Location: Canton, Michigan

Post by rsavin »

Well I'm sorry to say that I jumped the low pressure switch you showed me and it still wouldn't start (clutch would not engage). But like I said the light on the dash comes on when I push the compressor switch to on. So to test the clutch, I ran a hot lead (+) directly from the battery to the clutch wire after I disconnected it and sure enough it clicked in very firmly. I did not have the engine running when I did this and of course the key was off. I didn't want to take the chance of smoking something. I engaged the clutch for only a second a couple of times and it sounded very strong. So back to the original question and like I said at the beginning, (for a refresher of the problem)....Before all this it was cycling perfectly when I turned on the dash switch but very frequently with only very slight, but noticeable cooling. After several tries I got the freon connected. Turned on the switch and nothing happened. Okay 20 psi is too low...I jump the low pressure safety switch but still nothing. I'm thinking of going back to the direct wire to the clutch thing, only this time I'll start and run the engine, hook up the freon and direct connect the the compressor clutch so it will take a charge. I'll do a manual cycle of the compressor during filling. After a decent psi is achieved I'll reconnect the compressor to it's proper control wire and see if it works. Wadoyathink???

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