Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

68 SS 396 El Camino A/C issues

RHinkel764 on Sun June 29, 2008 10:01 AM User is offline

Year: 1968
Make: Chevrolet
Model: El Camino
Engine Size: 396
Refrigerant Type: r-12
Ambient Temp: 90
Pressure Low: 30
Pressure High: 200
Country of Origin: United States

Hey Partners:

Looking for anyone that might be able to help troubleshoot the issue I have with my A/C. My system is for a 68 El Camino SS with factory A/C and everything is brand new- Compressor, evaporator, condenser, dryer, expansion valve, hoses- BUT I have an ebay POA valve that "worked" and in fact was very clean inside and out. Here's my problem:

Went to charge the system today by a reputable a/c guy. The system was tested and was sealed- so the freon went in- this is an r12 system.

The air blowing at the vent is only 65 degrees at best on a 90 degree day today. When I move the selector lever fron "VENT" to "COLD", my blower motor only blows at the low setting- even when switched through med & high. When on VENT, all three speeds work fine.

Next, the evaporator tubes are cold and moisture is condensing on it but the air output is not so cold. Inside the car , the a/c box is very hot to the touch- right by the foot of the passenger. All the cables are adjusted and seals inside replaced prior to installation. Should this be so hot? I think I have a mixing problem here. When I drive the car- A/C disconnected- out on cold and hit the fan switch, I get very warm air.

Last on the EBAY POA valve, there are two fittings that go into the evaporator area- one drains the oil, the other goes to a "bulb" I believe. On the POA valve, the fitting to the bulb, has a screw in valve like a "shader" valve going into the POA valve- should this be there? I had a POA eliminator prior that had the opening wide open.

Any suggestions are welcome- by the way 90 degrees, high side 200, low 30 at 1500 rpm sitting idle.


Chick on Sun June 29, 2008 8:40 PM User is offlineView users profile

The "30" low side shows the POA is working. (they are set for 28.5 I believe) so your problem is most likely with blended heater core air. Clamp off the heater hoses and try it, as far as the fan speeds, make sure there isn't a vacuum line broken or off, giving the illusion of no fan speed change, aside from that, the fan speed and compressor operation are separate. Tackle one at a time..Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

fonebone on Sun June 29, 2008 10:08 PM User is offline

Your very hot plenum chamber at your feet leaves no doubt, as Chick said, your heater is flowing. If you have a "bone stock" GM setup, then you must have a diaphragm, vacuum operated shutoff in front of the intake. These were always a constant problem with diaphragm leaking,either/ or both/ coolant,air. If this is the case, and you have no small diameter,brown, hard plastic hose to the top of the unit, it will be open to full flow. Feel your heater hoses when warmed up. If they are hotter than blazes, then you have a problem at the shutoff. Your dash control, with A/C, has a rotating vacuum control that shuts off water through a small vacuum line running thru the dash and out to the water control unit. If it's not there, don't panic. Buy a 5/8" I.D. heater shutoff and put it in line with a choke cable running in and under the dash. NAPA has a great photo book of parts. Look in "heater shutoff controls". The 5/8" line runs into the heater,3/4" is the return, goes down to the water pump. I use this on my Caprice 350 for complete shutoff. The cable just tucks under the dash to the right of the column. If you want to stay stock, look around at the passenger side firewall, inside and outside for a small ,1/8" hard brown tubing that is probably brittle and broken off. This comes out of your dash control, thru the firewall and down to the shutoff valve. If you find it ,you can connect a small rubber tubing to it and go to the shutoff. Now, this assumes after all these years that the dash control unit can pull at least 11" of mercury, minimum, per the shop manual, to pull the shutoff completely closed. When they wear, they leak vacuum. Every time you stop the car, they bleed water thru it,causing hot water to go into the dash area. Mopar and many Fords had a positive, cable operated control that moved with the "temp" setting. All the way left shut all flow off. Simple, positive, and trouble free compared to the fancier GM setup. As you can see, there are so many ways the control will not work that I just put a manual shutoff in line. If you do not use the heater too much, you can always put a shutoff (quarter turn or knob) right at the manifold, and throw away that valve. That's about as positive a shutoff as you can get! Sorry to be so windy, but I replaced a lot of those valves in my garage days. Keep us posted as to your efforts!

Edited: Sun June 29, 2008 at 10:24 PM by fonebone

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.