AC accumulator draining too fast, high hi side

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gman4dx266
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Joined: Mon May 07, 2018 4:10 pm

AC accumulator draining too fast, high hi side

Postby gman4dx266 » Mon May 07, 2018 4:17 pm

Hello all. Novice AC tinkerer, so go easy on me.

I have an 05 Saab 9-7x 5.3L. (A Chevrolet trailblazer in different trim). To make it short, I had an inclination that the system was low on refrigerant, would cool at idle but kick out above 1200rpm or so. My gauge set indicated about 45psi on the low side, but the high side at idle (about 92° outside) was about 225. This is at idle. When at 1500 or anything higher, the high side shoots up to 3 or 400psi and the low side dimishes to single digits. I vacuumed and recharged with a new orifice tube and accumulator and the issue persists. The truck has dual electric fans that are on 100% and flowing well. The accumulator is sweaty, and I don't see any obvious indications of a broken or crimped line. Jumping the low pressure switch out helps to keep the compressor on until the high pressure transducer kills the clutch from high head pressure. This last go-around I tried a Variable orifice tube as a shot in the dark versus the standard .072 fixed orifice tube size. The system holds a great vacuum and both needles are equal with the system off. My high side needle flickers/flutters when idling if that helps. I don't know if that's typical or not. Thanks for any and all help!
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bohica2xo
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Re: AC accumulator draining too fast, high hi side

Postby bohica2xo » Thu May 17, 2018 5:47 pm

Hitting the HPCO is a Condenser problem.

You say the fans are on 100%. Does it do the same thing when driving down the road above 40 mph?

What is the history of the vehicle? New to you?
gman4dx266
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Re: AC accumulator draining too fast, high hi side

Postby gman4dx266 » Thu May 17, 2018 7:16 pm

bohica2xo wrote:Hitting the HPCO is a Condenser problem.

You say the fans are on 100%. Does it do the same thing when driving down the road above 40 mph?

What is the history of the vehicle? New to you?


Unknown history. AC has never worked correctly since I e owned it. I have replaced the condenser, oriface tube, and accumulator, as well as flushed the lines and added the correct oil amount. Vacuumed down, left under vacuum over night, and recharged. The high side pressures still seem a bit high to me, about 225, and 40 on the low side, at idle. When revved to 1500rpm, the low side drops to about 25 or 20, high side goes to 300-315 and by this point the low side is under the cutoff and the clutch disengages. If I jump the low side switch it cools very well but Ice's up. If I charge it more to where it doesn't suck down too low it doesn't cool well at all. Almost a trade off. It doesn't seem like it's straining as much on the high side as it was before. Going down the road is the same behavior. It just seems like both sides are quick to react when compressor volume goes up. The only things left original besides the lines which are clean and clear, is the evap coil and the compressor and it's hard for me to bet either of those are at fault. I'd especially hate to have to tear the dash out but oh well.
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bohica2xo
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Re: AC accumulator draining too fast, high hi side

Postby bohica2xo » Thu May 17, 2018 8:12 pm

It is doubtful the evaporator is the issue.

To diagnose it correctly you need to charge the correct weight in to the system. You can't determine the charge level by pressure.

We also need temperatures to relate to the pressures. If your ambient temperature is 72f, 315 on the high side is bad indeed. Not so much at 104f

Vent temps help too.

Normally on a properly charged system it takes a lot of heat load to keep a CCOT system from cycling. Your description of icing up with the cycling switch shorted is a normal condition.

Once you have weighed in a charge, do a full load test.

Doors open, cabin fan on highest speed. Raise engine RPM to 2500+, and hold for 90 seconds. While engine is at 2500+ record the High & low side pressures as well as both the ambient temperature and the vent temperature.

Post the results here.
ice-n-tropics
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Re: AC accumulator draining too fast, high hi side

Postby ice-n-tropics » Sat May 19, 2018 9:32 am

Think you have a TRSA105 scroll compressor which normally causes gage indicator bouncing on the high pressure gage due to one discharge pulsation per revolution. Pressure data could be normal if ambient temps align. TPS (compressor thermal protection switch) seems ok becuse neuisance cycling seems to be caused by premature low side cycling not high temp discharge.
Restrictive accumulator or orifice tube fault was eliminated by parts replacement.
Restrictive internal evaporator or trash covered external evap surface or low side circuit with blocked circuit remains a potential, but rate of suction drop resulting in low side cycling becoumes an analysis tool.
Once had a similar problem due to dove feathers sucked up from passanger floorboard into evap inlet,
hotrodac
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bohica2xo
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Re: AC accumulator draining too fast, high hi side

Postby bohica2xo » Sun May 20, 2018 8:18 am

Yeah Ice it is a TRSA12B - still say there is an H missing there someplace...

Feathers? I guess Texans pluck chickens in their rigs. Mostly I see dog hair in evaporators around here.

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