The A/C in my 87 has been converted over to R134a, a few years back, and then it was fixed after it had been converted, because it had a leak (I guess). Now, it blows like a supercharger! but the air just really isn't cold. Could it be that I just need to have it charged, or do I have another problem? Thanks!

 

134a isn't as efficient as R12

Get a guage and check your pressure. It probably just needs a few ounces and you'll be good to go.


[Modified by Glock'94, 12:33 PM 4/15/2002]

 

Hopefully. I don't think that one line that's supposed to be HELLA cold...is even really cold at all. (Doesn't that mean it just needs to be charged?)

 

Usually, if you're low on coolant .. you will see ice on the lines going into the evaporator. This is more so with home A/C systems since they don't have a 200+ degree engine sitting right next to them to melt off the ice.

The reason behind the ice is because the lower pressure is allowing the high pressure gas to turn to liquid in the low pressure system too early and not where you want it to be (where air is blowing across coils making your air cold). It should occur after the expansion valve, but it's occuring before then.

Basically too low of a pressure of refridgerant will make the entire sytem the "low pressure" part of the system and cause the ice.

I think that's a good enough explaination... but anyway, go get a guage and check it :jester


[Modified by Glock'94, 1:26 PM 4/15/2002]

 

When I switched my ac from R12 to 134a I changed all a/c parts.Its blows COLD!

 

Actually, you have this backwards. The compressor takes the gas returning from the evap. (big line) compresses it, sends it into the condenser, as a hot gas, which then condenses it back to a liquid, at high pressure. This is then sent to the evap. as a liquid (small line) and when it passes through the metering device, it drops its pressure, boiling off inside the evap. absorbing heat to be taken back to the compressor and started all over again.

But back to your orig. question, is the compressor cycling on and off a lot? This to, is a sign of a low charge. IMO the two main problems people run into with the 134a conversion, or for that matter any refrigerant conversion is, They had a problem to begin with, ie: a leak etc. which needs to be fixed first. Secondly it is important that the correct amount of refrigerant be added to a system. To little and it will start boiling off in the line before the metering device, to much and it wont boil off in the evap. coil. The reason this is important is, the refrigerant absorbs its heat when it changes states from liquid to gas, and this needs to happen inside the evapator. Oh, and while im off on a tangent, let me tell you the defenation of a BTU. 1 BTU is the amount of energy (heat) it takes to raise 1lb of water 1 degree without changing its state. It takes 963? BTU's to change 1lb of 212degree water to 1lb of 212degree steam. This is the principle that is behind all refrigerant systems. The most heat is absorbed during the changing of the state of the refrigerent. That is why it needs to boil off in the evap.

 

Oops.. sorry :) ... yes, your right. I wrote that in a hurry and haven't been able to think clearly lately.

 

86 coupe steel heads/stock----a/c compressor won't kick in---service manual procedure leads me to the blower control module-Again!!--any ideas why module would fail?

 

Tim, when you get your car back come see me and we will look at your ac.