Air Conditioning help...it's serviced but blows hot, where do I start?

[AKcharger]

Trying to get the factory A/C running. I replaced the dryer, seals and serviced the A/C (134). the compressor kicks on but no cool. Where do I start? I'm ignorant on A/C

[b5blue]

Got gauges? Need high and low #'s. 

[Pete in NH]

Hi,

Need lots more information. Is this an original factory system(RV-2 compressor or newer compressor) and what year? Did you recharge the system into a vacuum? How much R-134A? And yes, system pressures would be very helpful. Also, tell us exactly what you did in servicing the system. Was the system open to air for a long time?

[ALBSURE1091]

I had same issue and it turned out the heater control valve was hooked up wrong so the hot water was still entering heater box and overriding the A/C. Once I hooked it up correctly the A/C was ice cold. This was on a 69 so not sure your system would be the same set up.

[AKcharger]

Thanks guys, sorry for lack of info:

-factory sys with RV-2 that was reportedly replaced last year, but previous owner said it never blew cold
- 134a, I had a trusted shop that only works old cars service it, they said it was serviced to specs but don't have #s. They had it all day and no leaks, they did put dye in just in case
- I had them de-service the system when I pulled the engine in Feb. So oil topped off and system evacuated
- system was open for 2 days as I pulled/painted engine and bay but I took great pains to cap/cover ever line/fitting and opening.
- I tried to Clamp off the heater hoses to test the heater valve theory but didn't really work

[Pete in NH]

Okay, Did the system blow cold when the shop returned it to you? That the compressor clutch kicks in says that there is a least 35 to 40 pounds of pressure in the system as a static level. But, that is no where near enough to produce cold air. It is concerning that the previous owner said it never really worked. Many rebuilt RV-2 compressors these days are junk so I would not discount the idea the compressor is bad. But, without pressure readings it's impossible to tell. Does the rear line going into the back of the RV-2 get cold. This is the suction line and it will get cold. The front line coming off the compressor is the discharge line and it should get too hot to touch. If these two lines are hot and cold respectively I would start to pay more attention to the hot water through the heater core theory.

AC work isn't really hard to do but so few really understand these old RV-2 systems today. You might check with a local auto parts store many will loan tools such as an AC gauge set. Pressure reading will help a lot in getting some understanding of what is going on here. I bought a gauge set and vacuum pump many years ago to do my own AC work and they have paid for themselves many times over. Not to mention no one understands these old RV-2 systems anymore. They can be converted to R-134A if done right.

[Nacho-RT74]

does actually blows HOT, or simply not cold ?

[AKcharger]

- got it back from shop serviced but not blowing cold (not hot, just not cold) they offered to dig more but I thought I'd play with it a bit. Good advie on gages pete, I'll do that. I understand on old cars that I'm often paying $80 for people to learn as opposed to paying for their skills and experience.
- Just no cold Nacho

[Nacho-RT74]

ok, that discards the heater valve!

[AKcharger]

well time to get some gagues, stand by guys for me info...

[John_Kunkel]

- got it back from shop serviced but not blowing cold (not hot, just not cold)

It could still be the heater. Feel both heater hoses, if they're both warm, hot coolant could be flowing through the heater core and warming the refrigerated air.

[AKcharger]

Thanks John, I'll check that 1st. if nothing I'll do what I do best...start throing parts at it

[71 SE3834V]

Check your blend door.
When I got my ac up and running it was blowing hot. Pinched of the heater hose and it cooled to lukewarm. Temp control valve was passing coolant. Got into the FSM and read that to warm up the conditioned air the system opens the blend door to pass air from the heater core. The arm for the blend door is located on the left side of the box near the accelerator pedal on the '71-72. Sure enough mine was stuck. A little WD40 and working it back a forth did the trick. Instant cold air.

[b5blue]

Put a small C clamp on one of the heater hoses before you even start the engine to test.   

[GT]

When running, is the line off the back of the compressor cold/have condensation?  It should.

You said it was converted to R134a.  Do you know what was done during the conversion? (Oil changed to correct type?  Barrier hoses?)

Was the EPR valve removed?   It regulates evaporator pressure around 26-28 pounds.   R134a likes it around 22 pounds.  That is why Classic Air recommends removing the EPR valve and using a thermostatic switch.  I have heard that some EPR valves are adjustable.

The EPR valve is on the back of the compressor, stole this off the internet:

[AKcharger]

Thanks Guys:
- Not sure if 70 is same but I'll check that blend door
- Tried clamp no real change
- oil and seals replaced...very sure that EPR valve was not touched
- will check for cold on compressor

unfortunatly I'm back in a work cycle so  will not be able to do much for a bit

[b5blue]

  Get a laser pointer temp. gun and next time you run it start looking for temp. differentials. Really if its working at all some line should get condensate fairly fast. This PIA crap is why I gutted my system and replaced with Classic's set. (My car has no "restored" value.)

[gtx6970]

Whats the pressures on both sides of the system

a general idea they should be in the 35-50 on the low side and 185 to 220 on the high side,,,approximatly

A guy here local just went thru a similar issue. turned out to be the aftermarket expansion valve.
He found and put an NOS one on it and the car blows ice cold , he was having low pressures on the high side I think

[AKcharger]

OK guys sorry for such a long delay...I just got lazy. Anyway I bought some gages and ready to start in ernest. 1st thing I did was start car and go "Max AC" the front line immediatly gets hot, the after line just remains the same, no cool or hot...just the same.

So next thing to check is??

[b5blue]

What are high and low pressures reading? You are certain the clutch has engaged the compressor? 

[AKcharger]

I had mrs turn on AC while I was watching and yes clutch engages (thought makes some noise on start up) I didn't check pressures as I was unsure if they are checked static or under load

[b5blue]

It's done running.

[green69rt]

Not sure about this and woud like to hear NHpete chime in.  Just from the clues, I would suspect a bad compresor.  Some garages dpn't know how to prep a new compressr for running.  One improtant step is to turn the compressor, by hand, thru several revolutions to distribute the oil.  I don't know why this is so important, maybe Pete can explain.  Really need those pressure readings.

[b5blue]

https://www.youtube.com/watch?v=80jSH8VQZms   Watch this and look for more.

[will]

Isn't there a window in the receiver? Can you look in the window and see if there's any liquid? I'm going by memory so maybe someone else who has more current experience will tell me I'm wrong.