SOLVED Volvo 850 a/c system only takes 17 oz. refrigerant? Topic is solved

Post by **JimBee** » 05 Jul 2017, 14:16

All the o-rings had been leaking on this a/c system so I cleaned up the connections and installed new o-rings. I pumped it down for about 7 hours and it held max -30 vacuum for two days.

Also removed a clutch shim to get exactly to .3 mm, and replaced the dryer. Dryer got about 3 oz. PAG 46 oil and about 2.5 oz. in the compressor after draining the little that was in it.

At 17 oz. of R134 (most of the 18 oz. can), I had 65 degrees at dash vent (a/c and fan fully on). Can was cold so I disconnected to warm it up. When I touched the high pressure line it was very hot. When I reattached the refrigerant hose coupling there was pressure showing on the refrig't gauge in the middle red zone. The dash temp had gone back up to around 90 degrees which was the temp before I added the R134. I shut it down. Which is where I am now. The gauge is touching the "overfilled" zone.

On my other 850, did similar dryer, o-ring refurb, PAG, etc, and on that one I got about 20 oz. in for IIRC around 45 degrees at the dash.

I'm confused about how much R134 should be in the system starting from none. Or what to do next.

Comments?

Post by **abscate** » 05 Jul 2017, 15:17

It should be on the sticker under the hood - AC charge. I suspect its about 750g or 750/28 = 27 ounces R134A

You are about half charged.

25C of temperature delta with car running at 1500rpm, high fan, recirce mode, 15 minutes isnt great performance.

Post by **JimBee** » 05 Jul 2017, 16:27

The problem is the filler port was showing high pressure ~ 130 psi when I reconnected the R134 hose and the gauge needle was touching "overfilled" when I squeezed the trigger. Plus the dash temp went from ~65 F (with ~16 oz. of R134) back up to ~90 F as I added more, but that's where it was when I started.

Engine has been off for around two hours.
I just reattached the R134 hose to get a pressure reading, it's ~115 psi.

What should be the pressure on that low side line when fully charged?

Post by **sleddriver** » 05 Jul 2017, 19:10

What type of gauge are you using JB? Is it a real quality A/C pressure gauge or a cheapy on top of a can?

You haven't filled in your location, thus I don't have any clues about your climate. If hot & humid, the supply line should be sweating downstream of the cap tube/flow rater. Likewise so should the suction line. If you've only 'installed' 17 oz. as previously suggested, that isn't enough for a system that was completely evacuated.

Post by **abscate** » 05 Jul 2017, 19:24

The temperature went up because the compressor cycled off, probably due to low refrigerant.

The gauges on the cans are not accurate, but moreover the reading of low pressure side is only meaningful when the system is running.

If you out the gauge on the car shut off , you will measure anywhere from 20-130 psi depending on where the refrigerant is sitting.

You can put the can into warm water to speed loading of the charge.

I'll try to find and link to jimmys AC thread, he is the expert on this stuff

Post by **JimBee** » 05 Jul 2017, 21:47

Today, in Minneapolis, MN, ambient temp was around 90 F and it was quite humid.

abscate: The R134 flowed quite freely for about 12 oz., then I warmed it in the sun and added some more. The clutch had stopped cycling and was fully engaged when the dash temp came down to ~ 65 F. When I got about 5 more oz. in I think the clutch was engaged, but with can warmed it wouldn't take any more AND the dash temp went back up to ambient, ~ 90F.

That's when I noticed the high pressure line was very hot and I'm pretty sure the clutch was engaged, but it wasn't taking refrignt so I quit there and turned turned off the engine. I haven't tried it again. I'd like to better understand it first.

I'm wondering if the high pressure switch is bad. What would that do?

Post by **abscate** » 06 Jul 2017, 04:18

Is the clutch dropping out or is it still engaged ? I'm sure you are still low charge at only 17 ounces

Hot high pressure side is ok.

It can take 30 minutes to get the full charge in with cans , even 45 minutes

Post by **JimBee** » 06 Jul 2017, 06:24

What concerned me is I think the clutch was engaged. Initially, it clicked on and off, but at about 16 oz. it was holding engaged. As I said, I got a little more in but it wouldn't take the final oz. from the 18 oz. can and the temp at the dash that had been cooling down from the initial ~ 90 F, stopped cooling and shot back up to ambient temp ~ 90F.

Since there's some question about gauge accuracy, I still have the gauge set I used to pump it down. A little later this a.m. I'll attach that and get a pressure reading.

This thread doesn't resolve anything but does mention a condition that might explain what's happening to mine. If the evaporator freezes b/c the pressostat isn't working, it will block flow. That could explain why my dash temp that had cooled to 65 F stopped cooling and the temp went back to ambient, ~90F.
http://volvospeed.com/vs_forum/topic/21 ... ressostat/

Tobster · Post by **Tobster** » 06 Jul 2017, 07:05

The information I got is you should use .29 oz. or .85kgs. ,I use kgs. but when systems wont take Freon because they are to low I will jump pressure switch to get compressor going to pull more in. If you start it up and it works for few minutes and stops and the pressures went way up so high pressure switch shuts it down, the cooling fans have to be on or pressure will sky rocket, or you said freezing up, air in system will cause freeze up, or stuck expantion valve sticking, or plugged orifice tube, pressure line should always be pretty warm. Not sure if any of this helps , got to have ac its to hot out.

Post by **JimBee** » 06 Jul 2017, 09:49

Tobster: Thanks for the pointers.

My engine cooling fan was coming on, so I think that's okay.

I didn't change the orifice tube only b/c it's so hard to access on the 850. That could be a suspect.

I pumped it down for 7 hours so I feel pretty sure there's no air or moisture in the system.

I do suspect the high pressure switch.

I'll start it up again. Theoretically, with the a/c activated, I should at least be getting cool air b/c it was cool (~ 65F) before it went back to cabin temp which was around 90 F. No R134 was lost when it got hot again. If all the controls are working properly, and the clutch stays engaged, it should at least be consistently cool like it had been. If it starts cool and suddenly gets warm again and the clutch is still engaged, then I'm thinking that a blockage would seem likely—most likely a freeze-up and not the orifice tube.

I assume that if the orifice tube was blocked, there would be no cool air at all.

Comments?