134a pressures

134a pressures

Postby justinf89 [OP] » July 8th 2011, 10:46pm

Ok I need some help. I recently replaced the compressor, front evaporator, and accumulator. I added the right amount of oil(I think), 48oz of freon like specd, and within a couple of days, the ac temp kept rising so I knew I had a leak. It wasn't enough to kick out the low pressure switch but I didn't know how much I had lost. To remedy the leak, I stuck on the high and low valves that come with the gauges and just closed them. Since then, the temps have been a steady 60 degree at idle, and about 52 on the interstate is the lowest I've seen for the past 2 months.

Anyway, today I decided to add some more freon. The problem is I don't know how much to add. My problem is I don't really know everything about reading the pressures. Am I supposed to get the low and high pressure reading at idle or at 2k rpm? Before I added the freon, at idle, both front and rear fans at max(well front on 3/4 due to faulty resistor pack), ac on max, the low side pressure was about 35 so I decided to add some freon. The chart that came with my gauges from interdynamics says 50-55(low)/275-300(hi) for an ambient temp of 90-100 but it doesn't say at what speed. I added about half a can(small one), and at idle the pressure jumped up to 56(low)/235(hi). I also took the reading at 2k rpm - 49(low)/285(hi). I know 285 is a bit high but the condenser was probably pretty hot by now, with really no air moving across it sitting in the driveway. Maybe I could hose it down while taking the readings?

Did I put too much freon in? I don't want to ruin the new compressor but the temps are still not as cold as my other 2 vehicles. I jumped on the interstate and it only got down to 48. I think I'm going to try and clean the condenser now with some de-greaser and see if it helps cool it down. Another thought I have is maybe the blend door's aren't working right. The accumulator is sweating pretty good too so I know it's working alright. Should i look into another problem and just assume the freon is fine?

Any help would be greatly appreciated. Thanks!
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Re: 134a pressures

Postby chevymaher » July 8th 2011, 11:22pm

Any air conditioner actually works better with a lower amount of refrigerant in the system.If pressure is to high(level of refrigerant to great)It stays liquid within the evaporator.If it staying liquid halfway through the evaporator then that half is not absorbing BTUs(cooling).The liquid vaporizing is what absorbs the BTUs.So optimally it starts at beginning of evaporator and has completed at the end.The idling and not moving,warmer air temp out of vents, is due to the poor air flow through the condenser thats why temps lower when moving.If your accumulator is having condensation system is getting cold enough inside.Check your blend door to see if you are getting heat mixed with it.Other concern would be dirty evaporator.Lint and dust build up blocking flow through it.I have went on air conditioning calls where 2 things were all that were wrong.Plants ivy being worst offender growing over condenser.Pull the plants off clean it with condenser cleaner.And two just like the lint trap in your dryer.A layer of wet lint over the evaporator both blocking air flow.On the evaporator I just blow it out with compressed air ,spray it with cleaner and blow it off again.In the van getting to the evaporator thats the trick.
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Re: 134a pressures

Postby justinf89 [OP] » July 8th 2011, 11:38pm

I'm going to try to clean out the condenser. How can I check the blend doors? Do my pressure's look too high? Thanks!
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Re: 134a pressures

Postby chevymaher » July 9th 2011, 12:00am

I have a 94 safari no rear air all original equipment.mine is ICE cold driving.Still better out the vents than most at idle.I just went and checked what I got.I dont check high side on cars just low.According to my gauge 25-45 is filled 45-65 is yellow warning zone.I have 30 oz of refrigerant in mine.At 70 degree ambient temp in the basement van cool.I have 45 lbs low side pressure under these conditions with air on max.At idle it took 30 seconds to go from 55 lbs at initial start-up to a steady 45 lbs on the low side.
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Re: 134a pressures

Postby sfeaver » July 9th 2011, 12:07am

When you first replaced your parts did you add only the oil that came out plus a couple ounces? or the entire capacity. Did you vacuum out system before filling?

As for temps at idle, with a good clutch it should be moving tons of air over that condenser. You need to figure out your lo and high side pressures, and at what ambient. Pressures will be higher if van is hot inside versus already cooled off.

A good rule of thumb is about 2.2 to 2.5 times the Ambient for a high side. It will cool better at 1500rpm than at idle. But like I said it should be roaring like a jet engine!

49 low side works out to 53 degrees, 285 is 158. To me I think your overcharged. But a bad fan clutch will do this too. Try spraying water and cool it down. If you have thermocouples you can see condensor in and out and see your drop.

If you didnt vacuum out before filling up, then the air and moisture is causing your problems! Another thing to keep in mind, with both evaporators on you have a huge heat load! If you have the rear off, when it cycles it will take a long time to cycle back on as you still have cold vapor coming from the back and keeping the pressure lower.

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Re: 134a pressures

Postby justinf89 [OP] » July 9th 2011, 2:01am

chevymaher, I really appreciate you checking that for me. I guess that means the chart I'm trying to go by is good for something because your's is dead in the zone for the temp.

Sfeaver, I didn't measure the oil I drained from the old compressor because it actually was a replacement for my original. I took it out of my parts van and the seals inside leaked so I didn't bother measuring it and I didn't have my original. I bought a 8oz bottle of oil and probably spilled 3oz pouring it in the new(3rd) compressor, so between the large front evap, the accumulator, and the compressor, I figured 5oz was good enough lol. I poured half in the compressor and the other half in the accumulator, which I spilled more. And of course I vacuumed it out haha. I did check the fan clutch and it was pretty tough to turn the fan at 95 out so I guess it's fine, unless it's slipping a lot when it gets up to speed. I'm sure it's original and at 180k miles, it's probably overdue. I know when the ac's on, and I'm sitting in traffic and it's 95 outside, the temps will slowly rise to over 220 and it keeps going up so I'll need to address that issue one day.

Ok so I cleaned the condenser, hosed it down while the ac was on, the pressure's plummeted of course. After I hosed off the condenser and got the high speed on the front fan working, the outside temp dropped to about 80-82. I rode up the street and back to dry it all off so I would get a good reading. I checked the pressure's again after the ac running in my driveway for about 5 min and the low was 40, and the high was 130. Sweat was all over the accumulator so I guess it's fine.

Earlier I actually called up interdynamics to ask about their chart and they said the pressure's listed for each ambient temperature are at idle.
At 80 degrees, the chart says 45-50 low, 225-250 high; so why is mine now so low? What gives? I know there's a lot of variables but it was steady at 40/130. I know I didn't lose any freon in 2 miles of driving. Maybe I cleaned the condenser soooo good lol. Now i'm rambling. I'm going to try it again tomorrow when the temps are back up in the 90's and post back. Right now I'm just worried about the pressure's, not the vent temp which I'll address later. Thanks for the help guys.
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Re: 134a pressures

Postby chevymaher » July 9th 2011, 2:08am

Cleaning the condenser will cause pressure to drop.It is working more efficiently and that means refrigerant temps are lower in the system.Thus lower pressures.
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Re: 134a pressures

Postby redfury » July 9th 2011, 2:10am

Nope there's a reading for low high side readings. I think you are a little low on coolant still. I'd add enough to bring the low side up to 45 @ 80 and see what the high side readings are. Are you using a gauge or just a depressor style checker? If you have a gauge and the needle is vibrating some, you may have failing reed valves in the compressor, which would account for low high side readings.
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Re: 134a pressures

Postby justinf89 [OP] » July 9th 2011, 2:21am

I've got a complete gauge set, tomorrow when it's hot, I'll check it again. If the readings are still low, I'll add some more. Thanks again guys.
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Re: 134a pressures

Postby justinf89 [OP] » July 9th 2011, 8:58pm

Ok well I haven't had time to check the pressure's again today but maybe tonight. I just wanted to let everybody know what an amazing difference it has been today, I actually had to turn the fan speed down from high because I was TOO COLD! On the interstate, it got down to 45 and it was 90 out so I'm pretty happy with that. I guess between the extra freon and cleaning the condenser, it really helped. It also cools down much faster now.
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Re: 134a pressures

Postby redfury » July 10th 2011, 3:42am

justinf89 wrote:Ok well I haven't had time to check the pressure's again today but maybe tonight. I just wanted to let everybody know what an amazing difference it has been today, I actually had to turn the fan speed down from high because I was TOO COLD! On the interstate, it got down to 45 and it was 90 out so I'm pretty happy with that. I guess between the extra freon and cleaning the condenser, it really helped. It also cools down much faster now.


Well, I'd say you're good to go then!
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