new compressor pumps but doesn't suck
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new compressor pumps but doesn't suck
Sounds weird I know. '99 4.6, put in a new compressor, accumulator and orifice tube. (Old fluid was clean, orifice tube was clean, old compressor was leaking, I did not flush system.) Vacuumed system and put maybe 6 oz. of R134 in the low side. Low pressure about 100, high 0--static. Compressor clutch wouldn't engage so jumped the low pressure switch and it does. Low side pressure DOES NOT GO DOWN with compressor running. High side does not come up.
Put enough R134 gas in the high side to get pressure to about 50. Tried again. Now High side pumps up to about 100 but low side still does not drop from about 90.
Wonder if I need to get more gas, or liquid, into the low side. Or, do I have a suction problem? Or.......
I've done compressors, repairs, etc. before but not run into this. Appreciate any help or advice you have.
Thanks!
Put enough R134 gas in the high side to get pressure to about 50. Tried again. Now High side pumps up to about 100 but low side still does not drop from about 90.
Wonder if I need to get more gas, or liquid, into the low side. Or, do I have a suction problem? Or.......
I've done compressors, repairs, etc. before but not run into this. Appreciate any help or advice you have.
Thanks!
Hotshot
Joined: Jan 2004
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From: St Louis
It's impossible for a compressor to "pump" but not "suck". In order for pressure to be built on the output side, refrigerant has to be sucked in the input side which is how it creates a pressure differential.
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
Please tell me you're not opening the high side valve with an R134a can attached!
BTW, you need at least 2 can installed to even begin to see the compressor start to work like it should.
BTW, you need at least 2 can installed to even begin to see the compressor start to work like it should.
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Thanks.
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Now, with the compressor engaged (jumpered), the low side is 55 and the high side is about 100. Low side does NOT drop at all when the compressor is engaged. High goes up from 55 to 100. No R134 is drawn from can. So, I guess it's pumping what's in there, but not drawing in any more? Possible Schrader valve problem, can problem, hose problem?? It did take 'some' 134 through this set-up.
Thanks.
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Hmmm, unless this compressor/set-up is different than all the other systems I've worked on, I'd think it should "work" with considerably less than 2 cans, if forced to engage.
Thanks.
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Hotshot
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you may have additional problems, I don't know at this point....... to START, you don't start the motor, but you put one can of R134 into the low port.. You add a second on larger systems... You should have a STATIC pressure of 90- 100 psi on the LOW and HI sides at this point... When you have a balance of about 90-100 psi, THEN you start the truck and engage the compressor... The LOW side will get sucked down to the 30-40 range and the HI will build up over 200 psi ........ depending on the ambient temp. ................... if you FORCE the compressor to run, the low side should suck down VERY LOW if your low on gas.
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That's pretty much the way I've always done it, and tried to do it this time. The problem is--I think--I probably got less then 1/2 a can to go in, at the outset. And can't seem to get more in. The question is why?
Thanks.
Thanks.
Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
You pulled a vacuum? Did you break the vacuum with refrigerant? Are you weighing the charge? I always start by liquid charging the high side with at least 50 percent of the charge. Then vapor charge the low, go off the refrigerant charge sticker.
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yes, yes, yes.
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I started over: Tried different manifold set, different charging hose, different can. Vacuumed the system, put in about 16 oz of 134 as a liquid, in the high side, which gave me a static pressure of about 85 on the high side. Jumpered the low pressure switch and started it up. Compressor engaged and high side went up to about 140 then slowly dropped to about 125. Low side started at about 82 and never dropped. Might have even gone up 1 or 2.
Talked to the compressor manufacturer--again--and though he wasn't the sharpest sounding tech I've talked to, his opinion was bad compressor. I hope it's that easy, but I still have a nagging feeling about an obstruction somewhere. Thoughts?
Thanks.
Talked to the compressor manufacturer--again--and though he wasn't the sharpest sounding tech I've talked to, his opinion was bad compressor. I hope it's that easy, but I still have a nagging feeling about an obstruction somewhere. Thoughts?
Thanks.
Hotshot
Joined: Jul 2005
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when you take the lines off the compressor, blow thru the lines and dryer and orifice to see that you have flow... You can use 1 can of R134 to push thru the system and see that you have no restriction............. the suction port is close to the compressor. If it will not drop to 30 psi, it would appear your compressor is not working........ I think the suction port is out the compressor side of the dryer ? So the dryer should not be plugged.