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Posted: 5/9/2007 3:05:07 PM EST
[Last Edit: 6/19/2007 8:11:09 PM EST by superdav]

My A/C started blowing hot air so i got some 134a with the little guage on it and charged until it said it was good (almost a pound) it blew cold for about 5 minutes then went hot again, It says it has a full charge and the compressor is kicking in. So WTF do i need to check now?
Link Posted: 5/9/2007 3:10:04 PM EST

Originally Posted By superdav:

My A/C started blowing hot air so i got some 134a with the little guage on it and charged until it said it was good (almost a pound) it blew cold for about 5 minutes then went hot again, It says it has a full charge and the compressor is kicking in. So WTF do i need to check now?

What vehicle are we working on?

Those cans with the dinky little gauges on them are bullshit, BTW; gauge readings even with a set of manifold gauges are no accurate way of telling how much (if any) refrigerant the system needs. It's a good chance you may have overcharged it, and an overcharged system won't cool any better than one that's undercharged.
Link Posted: 5/9/2007 3:30:12 PM EST
It's a 96 nissan truck, sticker says it holds 2 pounds, the guage showed low until the charge opened and after opening the charge the clutch engaged
Link Posted: 5/9/2007 3:36:34 PM EST
Evacuate, vacuum, properly charge system then go from there.
Link Posted: 5/9/2007 4:48:45 PM EST

Originally Posted By superdav:
It's a 96 nissan truck, sticker says it holds 2 pounds, the guage showed low until the charge opened and after opening the charge the clutch engaged

Evacuating and recharging the system would be the best thing to do for starters, so we can make sure that the proper amount of refrigerant is in there.
Link Posted: 5/9/2007 5:10:37 PM EST

Originally Posted By Quintin:

Originally Posted By superdav:
It's a 96 nissan truck, sticker says it holds 2 pounds, the guage showed low until the charge opened and after opening the charge the clutch engaged

Evacuating and recharging the system would be the best thing to do for starters, so we can make sure that the proper amount of refrigerant is in there.

Don't forget the PAG oil! Make sure you have a proper amount in the system.
Link Posted: 5/9/2007 6:12:24 PM EST
Evacuate and charging the system is useless without repairing the leak first. It could be one of two things, first have you attemped any sort of leak checking? The leak may be so large that it is leaking out very quickly. Shut the car off and listen for leaks, or use soap bubbles on all refrigerant fittings.
It could still be low on refrigerant, holds two pounds and you only added one. Now adding more refrigerant could cause problems because you don't want to overcharge it. You could start from scratch and add two pounds and see what happens. What you do with the refrigerant already in the system is up to you, remember it is illegal to vent refrigerant to the atmosphere.
With the compressor running, the large refrigerant line should be cold at the compressor and you should see around 55-75 psi at the suction line (large cold pipe).
If it still does not work you have other problems and at this point I would take it to somebody who knows how.
Link Posted: 5/31/2007 8:36:12 PM EST
Back at square 1
Ran vacuum pump for an hour, shut off pump left the guages hooked up for 4 hours while i went to kids baseball games when i got back the vacuum was holding at 25inHg after 4 hours I think its safe to assume there is no leak. I then connected the first can of 134a and it sucked it down like a hoover, high side 100 psi, low side 28inHg,
second can went down like the prom queen, high side 145 psi, low side 30inHg
The manual i have on the truck says with 2 pounds of 134a, 28inHg on the low and 2.2 times the current air temp for the high, its 70 degrees outside so 154psi
and it still blows hot air!
Link Posted: 6/1/2007 3:28:24 AM EST

Originally Posted By superdav:
Back at square 1
Ran vacuum pump for an hour, shut off pump left the guages hooked up for 4 hours while i went to kids baseball games when i got back the vacuum was holding at 25inHg after 4 hours I think its safe to assume there is no leak. I then connected the first can of 134a and it sucked it down like a hoover, high side 100 psi, low side 28inHg,
second can went down like the prom queen, high side 145 psi, low side 30inHg
The manual i have on the truck says with 2 pounds of 134a, 28inHg on the low and 2.2 times the current air temp for the high, its 70 degrees outside so 154psi
and it still blows hot air!

in/hg? The low side is pulling into a vacuum? Um, no, that's not the way it should be.

Rough rule of thumb, at hot idle with the compressor running, take the ambient temp and divide by two. That should be your low side pressure. Take the ambient temp and multiply by two. That should be your high side pressure.

If the low side is pulling into a vacuum, you've got a restriction somewhere. If I was to take a swag, I'd say at the expansion valve. Maybe the receiver/dryer came apart and threw desiccant through the system, stopping the expansion valve up.
Link Posted: 6/1/2007 8:39:51 AM EST

Originally Posted By Quintin:

Originally Posted By superdav:
Back at square 1
Ran vacuum pump for an hour, shut off pump left the guages hooked up for 4 hours while i went to kids baseball games when i got back the vacuum was holding at 25inHg after 4 hours I think its safe to assume there is no leak. I then connected the first can of 134a and it sucked it down like a hoover, high side 100 psi, low side 28inHg,
second can went down like the prom queen, high side 145 psi, low side 30inHg
The manual i have on the truck says with 2 pounds of 134a, 28inHg on the low and 2.2 times the current air temp for the high, its 70 degrees outside so 154psi
and it still blows hot air!

in/hg? The low side is pulling into a vacuum? Um, no, that's not the way it should be.

Rough rule of thumb, at hot idle with the compressor running, take the ambient temp and divide by two. That should be your low side pressure. Take the ambient temp and multiply by two. That should be your high side pressure.

If the low side is pulling into a vacuum, you've got a restriction somewhere. If I was to take a swag, I'd say at the expansion valve. Maybe the receiver/dryer came apart and threw desiccant through the system, stopping the expansion valve up.


You're right i was looking at the wrong numbers
So if i change the expasion valve is this going to happen again if that is the culprit? Any way to flush the system and make sure it is clean?
Link Posted: 6/19/2007 8:08:53 PM EST
new exspansion valve, complete flush, vacuumed, charged with 12 oz AN I GOT COLD FREAKIN AIR!!! There was alot of shit that came out of the condensor, The manufacturer calls for 2 pounds of 134a I put in 1 pound and got cold air, 220psi on the high 30psi on the low should i be satisfied or put in the other pound? I dont have a thermometer.
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