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ac not blowing as cold...r12 system using r134a freon

lv6l on Sat April 19, 2008 3:28 AM User is offline

Year: 1994
Make: honda
Model: civic
Engine Size: 1.6L
Refrigerant Type: r134a
Ambient Temp: 80F

i have a 94 honda civic. i put in a ac system off a 92 civic. my 94 civic originally suppose to be r134a but the 92 is the older r12 system. so now pretty much to make a long story short my 94 is running r12 ac system. i vacuum the system out. charge it with r134a freon but it's not blowing as cold. i have no leak. my compressor turns on and off a lot though, causing my car to not drive correctly. i would like to know does the pressure sensor have to do with anything? why is my compressor turning on and off a lot. thanks.

mhamilton on Sat April 19, 2008 12:34 PM User is offlineView users profile

Well, first need to know what the high and low pressures are.

Changing to an R12 system is taking a step backward. The R134 condenser needs to be more efficient.

NickD on Sat April 19, 2008 5:36 PM User is offline

If your high side is >390 psi, your dual function switch will kill the compressor causing cycling, only other thing that kills the compressor besides the switch is the evaporator sensor and that is if that temperature drops below 33*F.

Have a feeling your system is near popping the cork, and you may also have air in the system, happens very easily when switching from vacuum to charging if you have to change hose connections.

mk378 on Sat April 19, 2008 7:14 PM User is offline

Measure that high side pressure it sounds like that's what's making it cycle off. It is remotely possible the pressure is normal but the switch is cutting out early.

But you're probably running too high. Is the condenser fan OK? These systems don't need a lot of refrigerant, about 18 oz. Also too much oil will get in the way and run pressures up. I thought they all had a PF condenser starting with '92 even though still using R-12 that year.

lv6l on Sun April 20, 2008 3:24 PM User is offline

well first off, is it okay to use r134a freon in a r12 ac system? i will check my high and low side and tell you guys what i see. should i check high and low when car is on with ac max? or car motor off? thanks.

mhamilton on Sun April 20, 2008 4:00 PM User is offlineView users profile

If the R12 system had the parallel flow condenser as mk378 said, then it should be okay. I don't know if there is any adjustment needed to the control valve that keeps your evaporator at the correct temp.

You need to take pressure readings with the compressor running, control set on max, doors open, with the engine around 1500 rpm.

lv6l on Tue April 22, 2008 6:43 PM User is offline

Ok, I got out to my car and start it up on a cold start. Idle was at 1.5k rpm. I put on the low side and high size nozzle. Open both side and wrote down the reading. On my gauge it read Low = MAX (estimate to be around 45-50) It has no numbers beyond 40 so that is what I got. on High = 47.5. My gauge has a lot of number, the number i wrote down is on the furthest outside of the gauge, it's marked "R134a". My AC feels cold when my car is warming up and I'm parked in one spot. I took it out for a drive and the AC feels like it was not as cold compared to when I was parked. When I parked it again, the AC seems to get a bit colder. This is all felt by my hand and I am unsure of the temperature, I will try to get a thermostat reading to get more of an accurate reading. But his is what's going on so far. My clutch on my compressor seems to be working normal. It runs constant with a few stops here and there. Before it was turning on and off constantly. What's up now? Is there something I was suppose to adjust when putting in R134a freon in a R12 AC system? Could my drier be bad? Can this cause not cold air? Thanks in advance for any inputs.

EDIT* I went out and look at my gauge and converted from my readings to the most inner numbers. Now on my gauge the most inner numbers says "inHg PSI" Low = 350psi (max) High = 165psi

Edited: Tue April 22, 2008 at 6:56 PM by lv6l

mhamilton on Tue April 22, 2008 7:56 PM User is offlineView users profile

Low side of 350 psi is not correct, should see 20-30 psi on the low side on a working system. Don't want to say "always," but you won't see a low side pressure higher than the high side. What kind of gauges are you using?

High side of 165 psi could be undercharged, but that greatly depends on ambient temperature.

If your system was originally R134a, then you should charge the factory amount, you won't need to adjust the charge level.

mk378 on Tue April 22, 2008 11:58 PM User is offline

Not sure what kind of gauge you're using. It's well worth it to spend the about $75.00 for a basic manifold set.

Check your water valve. This is a very common issue on Civics, if it is not closing fully the heater will start fighting the A/C when the engine warms up.

Does the low side pipeline under the hood get cold?

These cars cool good with R-134a. You don't have to modify anything except change the oil, and as part of that process, install a new drier which needs to be 134a compatible. Any recently manufactured one will be.

Edited: Wed April 23, 2008 at 12:00 AM by mk378

lv6l on Wed April 23, 2008 3:46 AM User is offline

I am using the 75.00 one. How do I check my water valve?. Yes, my low side pipe gets cold. So cold that it starts to have it's own cold water vapor condense on there like a cold glass of ice on a hot day.

I will get a picture of my gauge up by tomorrow hopefully for you guys to see.

Edited: Wed April 23, 2008 at 3:52 AM by lv6l

mk378 on Wed April 23, 2008 10:06 AM User is offline

That cold pipe indicates the refrigeration system is working fairly well. It sounds like there is cold air coming out of the evaporator but you never feel it because it gets reheated on the way to the vents.

The water valve is mounted on the firewall behind the engine and it controls the water flow thru one of the heater hoses. There is a push-wire going (indirectly) to the temperature slider on the dash. When you put the slider to full cold, the wire should come all the way out and push the lever on the valve until it stops. If you can move the lever further at the valve the cable needs to be adjusted. Unhook the clip holding the outer housing of the cable to the valve and pull the housing forward so the lever will move further. Then reclip the housing. Move the temperature slider back and forth and check again.

lv6l on Wed April 23, 2008 8:36 PM User is offline

Thanks. Will try this. Hope it works.

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