Help with AC rebuild

Sonny · Mar 4, 2018

1970 Belvedere with AC.
After rebuilding my heater box with new heater core and cooling coil, I’m ready to re-install cooling system under the hood. Some general questions:

I’m buying a rebuilt compressor from Summit that uses 134A. Is that what I need (134A)? Is it hard to take the clutch off the old compressor and put it on the new one? Special tools? Does 134A require replacing anything else?

Can I reuse all the original hoses/fittings?

Do I need a new drier for 134A?

I need a new condenser. Recommendations?

Assuming no change to the wiring?

Thanks!!!

snakeoil24 · Mar 4, 2018

You will need a new clutch and you can buy a brand new sanden compressor for 125.00 with clutch. need new drier for sure. Condensers are cheap so get one from any kit supplier. The ends on hoses are different. Any local hose maker can fit you up easily.

oldbee · Mar 4, 2018

The o-rings should be green color, not blk or orange. different oil used too( PAG oil). Definitely change drier. R12 is too expensive& hard to source.

JimKueneman · Mar 5, 2018

Is the original one still on the car (i.e. not a aftermarket rebuilt)? If so I would pull it apart and see if it is savable. The main things are

Are the cylinders scored
Are the reed valves bent or rusted
Do the bearing turn without any rough spots

If those are all ok I would just rebuild it. You can get a gasket kit (steel gaskets) and R-134 seal from Classic Industries. Here are some pointers:

https://www.forbbodiesonly.com/mopa...net-500-project.114333/page-18#post-910566430

The seal is complicated and I messed it up more than once. Here is how to really install it..

https://www.forbbodiesonly.com/mopa...net-500-project.114333/page-39#post-910641603

The old hoses are fine but as oldbee said you need R-134 o-rings (again Classic Industries have them). I just flushed my condenser out with alcohol and then blew it out good. For a replacement again Classic Industries has them and they are probably Classic Air parts.

ALWAYS use a new dryer it the system has been open for more than a few hours.

My thread will tell you to remove the EPR valve, that is important for it to work well. That said you are suppose to put a thermal cycling switch on the clutch because the system could freeze up. I just recognize it freezing up (air starts to get warmer) and I cycle it by hand (shut it off for a while or turn the fan up higher to move more of the cold air to the interior).

Trashdog67 · Mar 5, 2018

I used this kit. 100% new from the firewall forward. Just add compressor and brackets. They have those too. Easy peasy. http://bouchillonperformance.com/ac_condenser_kits

snakeoil24 · Mar 5, 2018

I have used Randy Bouchillion and was very happy

bearman · Mar 5, 2018

JimKueneman said:
Is the original one still on the car (i.e. not a aftermarket rebuilt)? If so I would pull it apart and see if it is savable. The main things are

Are the cylinders scored

Are the reed valves bent or rusted

Do the bearing turn without any rough spots

If those are all ok I would just rebuild it. You can get a gasket kit (steel gaskets) and R-134 seal from Classic Industries. Here are some pointers:

https://www.forbbodiesonly.com/mopa...net-500-project.114333/page-18#post-910566430

The seal is complicated and I messed it up more than once. Here is how to really install it..

https://www.forbbodiesonly.com/mopa...net-500-project.114333/page-39#post-910641603

The old hoses are fine but as oldbee said you need R-134 o-rings (again Classic Industries have them). I just flushed my condenser out with alcohol and then blew it out good. For a replacement again Classic Industries has them and they are probably Classic Air parts.

ALWAYS use a new dryer it the system has been open for more than a few hours.

My thread will tell you to remove the EPR valve, that is important for it to work well. That said you are suppose to put a thermal cycling switch on the clutch because the system could freeze up. I just recognize it freezing up (air starts to get warmer) and I cycle it by hand (shut it off for a while or turn the fan up higher to move more of the cold air to the interior).

Did you adjust your txv after you removed thoseepr valves

JimKueneman · Mar 5, 2018

bearman said:
Did you adjust your txv after you removed thoseepr valves

txv?

bearman · Mar 5, 2018

Yep its gold in color and should have thermo tape around it. Its a expansion valve . With gauges hooked up and rpms at normal idle get a reading of pressure. Now run rpms up to cruise speed and note the pressure. It seems to me if you are freezing up your low side is sucking down to far and damage will occur over time. Yes you can have a switch that will cycle clutch on and off but it will do it even faster with the rpms you run on the road. The second thing is find your low cut out switch on the low side take the connector off look down the middle of the switch might be a small adjustment screw that you can adjust to also help with freeze up. I hate to say this but chevy has adjustable switch on the low side and you can set your low pressure cut out lower than stock settings so when setting at a idle the clutch doesnt cycle all the time and keeps the onside colder

JimKueneman · Mar 5, 2018

bearman said:
Yep its gold in color and should have thermo tape around it. Its a expansion valve . With gauges hooked up and rpms at normal idle get a reading of pressure. Now run rpms up to cruise speed and note the pressure. It seems to me if you are freezing up your low side is sucking down to far and damage will occur over time. Yes you can have a switch that will cycle clutch on and off but it will do it even faster with the rpms you run on the road. The second thing is find your low cut out switch on the low side take the connector off look down the middle of the switch might be a small adjustment screw that you can adjust to also help with freeze up. I hate to say this but chevy has adjustable switch on the low side and you can set your low pressure cut out lower than stock settings so when setting at a idle the clutch doesnt cycle all the time and keeps the onside colder

Ah, so I set my low side pressure to about 34-36 lbs at my normal cruising RPM (2000 or so)..... I don't have a low pressure electrical cut off switch. It only seemed like it was freezing up last monsoon season (high humidity) and I running the fan on low.

At 65MPH it blows about 34-36 degree air out the vent.

bearman · Mar 5, 2018

JimKueneman said:
Ah, so I set my low side pressure to about 34-36 lbs at my normal cruising RPM (2000 or so)..... I don't have a low pressure electrical cut off switch. It only seemed like it was freezing up last monsoon season (high humidity) and I running the fan on low.

At 65MPH it blows about 34-36 degree air out the vent.

bearman · Mar 5, 2018

If you are set at 34 psi and its not freezing up that's fine but you are looking for 25 psi on the low side this drop roughly 3 more degrees and have a low cut out around 20 psi. Of course your high sode will climb up a little higher but nothing to really worry about. The txv valve should be adjustable you can set your superheat to what you want the evap temp to be and then you can run on low speed at 100 degrees all day

JimKueneman · Mar 5, 2018

bearman said:
If you are set at 34 psi and its not freezing up that's fine but you are looking for 25 psi on the low side this drop roughly 3 more degrees and have a low cut out around 20 psi. Of course your high sode will climb up a little higher but nothing to really worry about. The txv valve should be adjustable you can set your superheat to what you want the evap temp to be and then you can run on low speed at 100 degrees all day

How about you bring your tools and gauges the next time I come up for a show! :popcorn2:

Thanks for the tips. I'll play with it.

Nice writeup on all this!
http://www.emersonclimate.com/Documents/FlowControls/PDF resources/2008FC-21Troubleshooting-TXV.pdf

bearman · Mar 5, 2018

JimKueneman said:
How about you bring your tools and gauges the next time I come up for a show!

Thanks for the tips. I'll play with it.

Nice writeup on all this!
http://www.emersonclimate.com/Documents/FlowControls/PDF resources/2008FC-21Troubleshooting-TXV.pdf

Can do willing to help

bearman · Mar 5, 2018

JimKueneman said:
How about you bring your tools and gauges the next time I come up for a show!

Thanks for the tips. I'll play with it.

Nice writeup on all this!
http://www.emersonclimate.com/Documents/FlowControls/PDF resources/2008FC-21Troubleshooting-TXV.pdf

Yep thats the valve looking for at the bottom you can turn it in or out depending on what you want to do. Question were are you service ports at?

JimKueneman · Mar 5, 2018

bearman said:
Yep thats the valve looking for at the bottom you can turn it in or out depending on what you want to do. Question were are you service ports at?

At the compressor (there are 2 for low, one in the line at the compressor and one in the cylinder head of the compressor)

JimKueneman · Mar 5, 2018

Is there a superheat temperature you should be shooting for?

bearman · Mar 5, 2018

Ok the one in line at the compressor is the one you can go to you favorite a/c place and get a screw on switch then tap into your clutch wire and then you will have your cut out switch for for clutch get one that closes at 20 psi and reopens at 25 psi.

bearman · Mar 5, 2018

JimKueneman said:
Is there a superheat temperature you should be shooting for?

Yes i like to see around 8 to 10 superheat but it really depends on the car.

JimKueneman · Mar 5, 2018

You use use and IR gun to measure the temperature or a thermocouple taped to the metal hose to measure the superheat? And the remote bulb in the paper is where the capillary tube is stuck in the socket in the line correct.

Help with AC rebuild

It’s all fun til the rabbit gets the gun.

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