Classic auto air questions

[Pete in NH]

Dino,

Sounds like things are going well!  The compressor clutch should kick in very soon. You may want to use the pan of warm water trick to get the pressure up a bit.  It's bit cool here today, only about 70 so I would definitely have to use the warm water trick. Yesterday it was in the 80's the R-134 would have went right in.  But, even at 40 to 50 pounds static pressure you should be able to start the engine and compressor and get the oil moving around the system. With the compressor not running the pressure should be the same on both gauges. With the compressor started the suction side will be somewhere around 20 lbs and the discharge side should start coming up over 100 lbs. Remember, the discharge paddle wheel valve on the gauge set should be closed and you will work from now on with only the suction side valve.

[Dino]

Hi Pete,

Problem.  Compressor hub is not spinning and discharge side is at 80 psi.  What do I do?

[Dino]

I had to shut the car off, nothing is happening.  When I put the first can in the warm water, pressure went up to round 70.  When I though the can was empty I closed the valve and put the second can on, but I forgot to check the clutch.  I reopened it and pressure only slightly rose to around 80, it won't go past it and the clutch is not engaging.  I'm going to see if I get power to it.

[Dino]

When I got back to the car I saw the pressure was up to 110.  I started it back and opened the suction valve and pressure went back to 80.  I shut it of again and checked for power.  The way I have it setup is thermostatic switch to pressure switch to compressor.  Power goes into the thermostatic switch, I have near 12v's running the fan on high with max a/c on and the engine off.  But no power gets to the pressure switch and thus nothing to the compressor.

I am not going to work on this today so can I just close the can tap and suction valve and leave it like that for a few days? 

[Pete in NH]

Well, that's disappointing about no 12 volts to the pressure switch. You might try disconnecting the wires to the pressure switch and putting an ohm meter across its pins just to see if it's closed. It should be at 80 lbs. pressure.
I know that will not solve your power issue but it will tell you if you are good to go after you get power to the pressure switch.

If you are going to leave things for a few days, I would close the can tap and close both valves on the service fitting couplers on the gauge set and make sure both side wheels are closed on the gauge set. I would then disconnect the gauge set from the service ports. You may loose the R-134 left in the can if the can tap leaks. The system on the car should be fine until you get power to the pressure switch. You can reconnect the gauge set when you are ready to resume working on the system.

It's too bad you hit this little problem, I think you were well on your way to a working A/C system.

[Dino]

I got it to work!

The thermostatic switch is adjustable and has a lever on it.  As soon as I moved it. it clicked and the clutch engaged!

I'm not sure where the slider needs to be but I'll figure it out.  Now, with the third can hooked up, I filled a bit, then shut the suction valve and checked for pressure.  It never got much above 10.  Before I knew it the third can was empty and pressure is now between 7 and 17, depending on the rough idle of the engine.

It blows cold inside, but not a ton, I think it should be colder.  Should I get another can and try to add it?

[Pete in NH]

The factory fill of R-12 was about 42 OZ. CAA says 24 for their system. I think you are using the original factory evaporator which may be bigger than the CAA  system. You typically use about 80% of the R-12 charge weight for R-134 which would be about 33 OZ. for the factory system. Three cans gives you about 36 OZ, I would not add any more. You may in fact be slightly over charged. Run the engine up to 1500 RPM and see what your suction and discharge pressures are. Also. place a thermometer in the center vent and see what the temperature is compared to the ambient temperature.

On setting the thermostatic switch you want he coldest setting that will not allow the evaporator to freeze up. Since you are using kind of a compromise installation on the switch capillary tube, finding the right switch position is going to be trial and error. For right now set it as low as it goes and see what happens.

[Dino]

I'm sure a bit of refrigerant was lost with purging and likely the cans did not get fully drained either so I may be okay still.  At idle the suction read 17 or so for max and 7 for the low.  Right side was around 165.  Tomorrow I will rev it up and look at the pressure readings again.  I only closed the suction side valve, not he coupler valve, if that matters.  Since no more refrigerant should be added, can I go ahead and disconnect the gauges? 

I will try to find an accurate temp reading.  I was standing in the sun and was being baked by the engine heat so maybe the cool air coming out of the vents just didn't feel cold enough for me at that time.  Sometimes it's hard to say.  On an 85 degree day it may work fine but we touch the triple digits here sometimes.

I thought I had the switch set to the coldest but apparently that setting turns the power off.  I have it all the way to the other side which may be the low or warmest setting. 

I will report back tomorrow with my findings.

As always I sincerely appreciate your help.   

[Pete in NH]

Lets get the center vent temperature and pressure readings at 1500 RPM before adding any more R-134. So, yes, for now go ahead and disconnect the gauge set. This may take some "dialling in"to get things set up since its no exactly a stock system. But again, I think you're getting close.

[Dino]

Today is going to be fairly hot and humid so a perfect time to test the a/c system.  First I'm going to drive it a round a bit just to see what the a/c feels like. Then I'll take a temperature reading and measure the pressure on the system.  I'll report back with my findings.

[Dino]

Well that didn't happen.  Something came up and I didn't have the chance to do any work.  I'll try again tomorrow.

[Dino]

It seems my thermometer is not registering much but it's a moot point, the system is not working properly.  I adjusted the thermostatic switch a few times but that's not the issue, something else is going on.  I have not yet registered the pressure but my guess is it'll be around 10 psi like last time.

With max a/c on and fan on highest, at idle the air coming out of the vents is cool.  Not ice cold, just cool.  It would take the edge off on a hot day, but not by a ton.  Here's the funny part:  the faster I drive, the warmer the air becomes.  When I slow down, it becomes cool again.

I don't know why it does that but I think I may have to turn this over to a pro.  There's a mom and pop shop close by, they fixed my leaky radiator a few years back for a ridiculously low amount so I'll take it there next week or so and see what they can do. 

If you have any ideas I am happy to try something. 

[Pete in NH]

Hi Dino,

Two things to try-

1- Make sure the heater control valve is not letting any hot coolant through the heater core. Other wise the A/C and heater are fighting each other.

2- Lets get the gauge set back on there and get system pressures at 1500  RPM.

Also, I looked back through the thread but I'm not clear as to which Expansion valve you used and whether it was a new one or not.

[Dino]

Hi Pete,

The expansion valve is new.  I ordered the one with the single capillary.

The heater valve is in good shape, it shuts off perfectly. 

I'll get the pressure readings and will try another thermometer to get you some numbers.