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68 Chrysler A/C problem...question.

Posted By: StrokerPost

68 Chrysler A/C problem...question. - 07/02/13 07:10 AM

What is on the other side of the firewall from these 2 a/c lines? The a/c is not blowing cold, but the compressor, dryer and expansion valve have been replaced and the smaller of these 2 lines is very cold when engine is running but the other is not cold at all. Should they both be cold? Is there a control valve on the other side that maybe isn't working or is something plugged up? Any help/suggestions would be great. Thanks. If it matters, I noticed that the heater isn't blowing hot either.

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Posted By: BDW

Re: 68 Chrysler A/C problem...question. - 07/02/13 11:33 AM

The evaporator coil is inside the dash.

Posted By: therocks

Re: 68 Chrysler A/C problem...question. - 07/02/13 02:31 PM

One line will be cold the other hot.Thats how A/C works.The evaporator is on the other side of the fire wall and the heater core and box.Sounds like you have a blend door problem.Some use vacuum some cables.get a flashlight and look under the dash as you change modes.I hope its not an auto air syatem.if you dont have a factory manual its pretty much hopeless.even with it its a pain as they had a setup to check the auto air setup.Rocky
Posted By: Ply72rr

Re: 68 Chrysler A/C problem...question. - 07/02/13 07:03 PM

The smaller line going to the expasion valve is the high pressure side and should be warm. The larger hose which leaves the evaporator and goes to the suction side of the compressor should be cool.
Posted By: StrokerPost

Re: 68 Chrysler A/C problem...question. - 07/03/13 02:48 AM

Quote:

The smaller line going to the expasion valve is the high pressure side and should be warm. The larger hose which leaves the evaporator and goes to the suction side of the compressor should be cool.


I have just the opposite of that. I don't know how that can be cuz the lines can only be installed one way and the compressor can only turn in one direction. Can you think of any condition that would have the "hot line" "cold line" thing backwards?
Posted By: NITROUSN

Re: 68 Chrysler A/C problem...question. - 07/03/13 04:35 AM

What are your high and low pressure readings?
Posted By: StrokerPost

Re: 68 Chrysler A/C problem...question. - 07/03/13 05:12 AM

Quote:

What are your high and low pressure readings?


I'll have to ask the guy that was workin on it.
Posted By: Ply72rr

Re: 68 Chrysler A/C problem...question. - 07/03/13 07:19 PM

Quote:

Quote:

The smaller line going to the expasion valve is the high pressure side and should be warm. The larger hose which leaves the evaporator and goes to the suction side of the compressor should be cool.


I have just the opposite of that. I don't know how that can be cuz the lines can only be installed one way and the compressor can only turn in one direction. Can you think of any condition that would have the "hot line" "cold line" thing backwards?



You could have a restriction somewhere on the high pressure side.You could start at the compressor and feel the high pressure side of the system to see if the temp drops off at a certain place. The high side leaves the compressor and goes to the condensor in front of the radiator,then to the receiver dryer,then the expansion valve. The temp will drop after a restriction. You really should have gauges hooked up so you can see the pressures on both sides. I was wondering if you had a aftermarket compressor that could have the high and low hoses reversed.
Posted By: StrokerPost

Re: 68 Chrysler A/C problem...question. - 07/03/13 09:20 PM

Quote:

Quote:

Quote:

The smaller line going to the expasion valve is the high pressure side and should be warm. The larger hose which leaves the evaporator and goes to the suction side of the compressor should be cool.


I have just the opposite of that. I don't know how that can be cuz the lines can only be installed one way and the compressor can only turn in one direction. Can you think of any condition that would have the "hot line" "cold line" thing backwards?



You could have a restriction somewhere on the high pressure side.You could start at the compressor and feel the high pressure side of the system to see if the temp drops off at a certain place. The high side leaves the compressor and goes to the condensor in front of the radiator,then to the receiver dryer,then the expansion valve. The temp will drop after a restriction. You really should have gauges hooked up so you can see the pressures on both sides. I was wondering if you had a aftermarket compressor that could have the high and low hoses reversed.


Nope, all factory, newly rebuilt comp, new dryer and exp valve. I'll get as much info as I can then post what I find. Thanks.

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Posted By: StrokerPost

Re: 68 Chrysler A/C problem...question. - 07/03/13 10:01 PM

Ok, I have the pressure numbers, he said the high side was 150 and the low side was about 50 I think he said. He said his concern was the low reading on the high side, said it should be 200-250...sound right? I asked what he would attribute the low reading to and he said prolly a blockage. Whats your thoughts on the numbers?
Posted By: NITROUSN

Re: 68 Chrysler A/C problem...question. - 07/03/13 11:28 PM

Replace the expansion valve.
Posted By: StrokerPost

Re: 68 Chrysler A/C problem...question. - 07/04/13 02:44 AM

Quote:

Replace the expansion valve.

He did that, its on its second new one.
Posted By: a12rag

Re: 68 Chrysler A/C problem...question. - 07/04/13 03:54 AM

Just my two cents worth . . . if you have converted over to the 134 stuff, then according to Classic Auto Air (and other A/C places I have talked with), you have to remove the EPR and install a thermostat switch instead, because of the different pressure that the 134 vs the R12 operates at :


Mopar Upgrades
CONVERTING to 134a

Classic Auto Air

Until 1995, most cars with air conditioning used R-12 Freon refrigerant that is said to have a negative side effect of damaging the ozone layer and is no longer produced in most countries. Now, the industry standard is R-134a, which is an efficient absorber and carrier of heat without the ozone layer damaging issues of R-12. Contrary to popular belief, most cars originally equipped with R-12 can be converted to 134a and still keep you just as cool.

Recommended steps to converting your Ford R12 air conditioning system to 134a.
1962 & Newer Systems

Minimum Requirements:

Change or restore the filter-drier.
Drain the compressor oil and recharge with 134a compatible oil. (PAG or Ester Oil)
Insure that the system is clean and free of contaminants (Depending on component condition, this may be a simple matter of blowing out with compressed air or liquid flushing with an air-conditioning flushing agent)
Replace or restore all rubber hoses with barrier hose.
Remove EPR valve from compressor’s suction port
Install thermostat.
Charge with 134a between 70-80% of the original R12 charge amount.
Replace any o-rings with 134a compatible.

HELPFUL HINTS

Ignore the sight-glass. A properly charged 134a system will likely show bubbles in the sight-glass.
Typical 134a charge rate will be approximately 70-80% of the factory R12 charge amount.

Hope that helps. . .

Cheers

Mark
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