Another AC question
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
Another AC question
A couple weeks ago I posted here and asked about my AC because it didn't feel like it was blowing very cold. I was told the system was probably low and it probably just needed recharged.
I bought a bottle of R-134a that came with a hose and gauge on it and hooked it up last night.
For one thing (which I forgot to mention in the last post) the compressor was kicking on and off all the time while I had it running. I hooked up the hose, the gauge was reading like everything was fine.
I noticed that when the compressor kicked on, the pressure would build up to 45 PSI, then when it shut off it would bleed back down to 25 psi in 10-15 seconds and the compressor would kick back on again.
I added the contents of the bottle I got, and it goes longer between the compressor kicking on and off now but it still doesn't feel any colder.
What's the problem?
I bought a bottle of R-134a that came with a hose and gauge on it and hooked it up last night.
For one thing (which I forgot to mention in the last post) the compressor was kicking on and off all the time while I had it running. I hooked up the hose, the gauge was reading like everything was fine.
I noticed that when the compressor kicked on, the pressure would build up to 45 PSI, then when it shut off it would bleed back down to 25 psi in 10-15 seconds and the compressor would kick back on again.
I added the contents of the bottle I got, and it goes longer between the compressor kicking on and off now but it still doesn't feel any colder.
What's the problem?
Lead Driver
Joined: Feb 2002
Posts: 7,970
Likes: 595
From: Greater Austin, Texas
If your gauge was going up when the compressor was on then you hooked it up to the wrong line, the high (pressure) side goes up when the compressor is on and the low (suction) side goes DOWN when the compressor is on. If you for sure have it hooked up to the suction side and it is going up then you have a restriction, most likely a plugged orifice tube.
Senior User
Joined: Jun 2004
Posts: 205
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From: Florida
ok for one those guages are fubar. I had one yesterday that said i was at 50psi with little coolant in there. One way to determine if you are low on freon is to feel the accululator, it should be getting cool or cold when running for awhile. Also listen to the low pressure switch on the accumulator. If it clicks and the compressor shut off, u definately have low pressure
This is of course assuming your compressor is working ok. My recommendation is if you want to add refrigerant use a hose without the guage and use small 12oz cans. This way u know how much u are adding. Some of these "big" cans are way too much for your system. Also add it slowly and be patient.
You really should have the system put on real guages and see if it is blockage, compressor or refrigerant
This is of course assuming your compressor is working ok. My recommendation is if you want to add refrigerant use a hose without the guage and use small 12oz cans. This way u know how much u are adding. Some of these "big" cans are way too much for your system. Also add it slowly and be patient.
You really should have the system put on real guages and see if it is blockage, compressor or refrigerant
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
Well the instructions on the thing told me the low pressure line was the one between the compressor and the evaporator (in the dashboard, as it said)...so I figured it was the fitting on the passenger side. Is is actually the one on the driver's side, between the compressor and...whatever the hell the thing in the front of the truck is, the accumulator or whatever?
Posting Guru
Joined: May 2007
Posts: 1,208
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From: North Reading Mass
It sounds like the compressor is cycling. The low pressure cutout will cycle on when the suction pressure reaches about 45 psi and cycle off when it drops to about 25 psi. If the pressure is dropping rapidy when the comp kicks on it might be still low on r 134a. As stated above it cold also be a restriction in the system. Get a gauge manifold set with the proper hoses for r134a auto fittings, or bring it to a shop. I work on commercial HVAC systems and would never add refrigerant unless I can see both the high and low side pressures. The accumulator is located near the firewall on the pass side.
regards
rikard
regards
rikard
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
So again...which side is low pressure? Drivers side or passenger side?
Also, I may have found part of the problem just a little while ago...I pulled out my blower motor resistor because I had been getting a burning smell on anything but high. When I pulled it out I found a bunch of crap up inside the box, apparently some little furry buggers got up in there and made a nest, and a bunch of stuff was up against the evaporator.
I pulled the blower motor out and removed a bunch of that stuff, so next time I have the truck out I'll have to try the AC again and see if it's any better. I do still wonder about the compressor cycling so frequently though.
Also, I may have found part of the problem just a little while ago...I pulled out my blower motor resistor because I had been getting a burning smell on anything but high. When I pulled it out I found a bunch of crap up inside the box, apparently some little furry buggers got up in there and made a nest, and a bunch of stuff was up against the evaporator.
I pulled the blower motor out and removed a bunch of that stuff, so next time I have the truck out I'll have to try the AC again and see if it's any better. I do still wonder about the compressor cycling so frequently though.
Fleet Owner
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From: Easton,Ks
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Posting Guru
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From: Cottage Grove, WI
having your evap core plugged up was one problem, but ill almost guarantee that it is not 100% fixed. You need to take it in and have someone who knows what theyre looking at see whats going on.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
A couple weeks ago I posted here and asked about my AC because it didn't feel like it was blowing very cold. I was told the system was probably low and it probably just needed recharged.
I bought a bottle of R-134a that came with a hose and gauge on it and hooked it up last night.
For one thing (which I forgot to mention in the last post) the compressor was kicking on and off all the time while I had it running. I hooked up the hose, the gauge was reading like everything was fine.
I noticed that when the compressor kicked on, the pressure would build up to 45 PSI, then when it shut off it would bleed back down to 25 psi in 10-15 seconds and the compressor would kick back on again.
I added the contents of the bottle I got, and it goes longer between the compressor kicking on and off now but it still doesn't feel any colder.
What's the problem?
I bought a bottle of R-134a that came with a hose and gauge on it and hooked it up last night.
For one thing (which I forgot to mention in the last post) the compressor was kicking on and off all the time while I had it running. I hooked up the hose, the gauge was reading like everything was fine.
I noticed that when the compressor kicked on, the pressure would build up to 45 PSI, then when it shut off it would bleed back down to 25 psi in 10-15 seconds and the compressor would kick back on again.
I added the contents of the bottle I got, and it goes longer between the compressor kicking on and off now but it still doesn't feel any colder.
What's the problem?
With the system off and at rest the pressure on both the low and high side should be about 80-95 PSI on a charged system.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
There is not anyway he saw what he said he saw unless the compressor was pumping backwards. And that is not possible.
Elder User
Joined: Feb 2007
Posts: 601
Likes: 1
From: Chicagoland
With the 134a systems the high-side connector is bigger than the low-side so you would need to work very hard to get connected backwards.
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