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I am armchair engineer. My scale is analog, not scientific like Renton.
Installing Classic Auto Air in a '70 Charger
- Thread starter Kern Dog
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This system has been a pain in the ***.
The heater and defroster work GREAT but it is getting WARM out there, just when the cold air from the car would be nice to have.
Over 3 weeks ago, the wife and I headed out for the Spring Fling in southern CA. The A/C was blowing cool-ish as we left in the morning but halfway to meet our caravan crew, it was blowing ambient temperatures.
We did the event with our friends and on the way home, Randy offered to take a look and see if he could do a fill and get the air blowing cold.
It worked! The air wasn't as cold as a new car but it was cooler than the outside of the car so I was happy enough.
A few days passed.
I went to drive the car and the air blew warm again. There are no obvious leaks anywhere so what is the problem?
Today we tried again. Randy changed the Schrader valves in the high and low side ports, tightened a few semi-loose connections and put a vacuum on it.....the standard 30" for 35-40 minutes. It held and did not move the gauge so he filled it.
Cold air through the vents again, not quite as cold as a new car but I figured that since the car sat in the sun awhile, the dash was hot and it takes a bit for cold air to blow even in new cars. We figured it was fine. He sprayed soapy water on all the connections and saw no bubbles so all appeared to be fine.
I parked it out in the lot, closed it up and we went for lunch and when we came back, I hung around Randy and Dean for at least another hour.
Time to go, I started down the road and the air blew warm and never got cold. 78 miles home in low 90 degree weather with no A/C.
Now, for the most part, I'm okay without A/C but the wife likes it. She is not a complainer but to entice her to go on road trips, the cool air is a nice perk.
I felt like a dork when I charged the system and it didn't seem to work but now that a more skilled guy has had similar luck, I know that whatever problem is there, it isn't something simple. I may use the shop that I used awhile back to find the leaks in Dwayne's car.....
These shops have more advanced leak detection stuff so maybe they will be able to track it down and get me fixed up.
I do appreciate the efforts put forth by Randy. He gave a few hours of his time and asked nothing in return.
The heater and defroster work GREAT but it is getting WARM out there, just when the cold air from the car would be nice to have.
Over 3 weeks ago, the wife and I headed out for the Spring Fling in southern CA. The A/C was blowing cool-ish as we left in the morning but halfway to meet our caravan crew, it was blowing ambient temperatures.
We did the event with our friends and on the way home, Randy offered to take a look and see if he could do a fill and get the air blowing cold.
It worked! The air wasn't as cold as a new car but it was cooler than the outside of the car so I was happy enough.
A few days passed.
I went to drive the car and the air blew warm again. There are no obvious leaks anywhere so what is the problem?
Today we tried again. Randy changed the Schrader valves in the high and low side ports, tightened a few semi-loose connections and put a vacuum on it.....the standard 30" for 35-40 minutes. It held and did not move the gauge so he filled it.
Cold air through the vents again, not quite as cold as a new car but I figured that since the car sat in the sun awhile, the dash was hot and it takes a bit for cold air to blow even in new cars. We figured it was fine. He sprayed soapy water on all the connections and saw no bubbles so all appeared to be fine.
I parked it out in the lot, closed it up and we went for lunch and when we came back, I hung around Randy and Dean for at least another hour.
Time to go, I started down the road and the air blew warm and never got cold. 78 miles home in low 90 degree weather with no A/C.
Now, for the most part, I'm okay without A/C but the wife likes it. She is not a complainer but to entice her to go on road trips, the cool air is a nice perk.
I felt like a dork when I charged the system and it didn't seem to work but now that a more skilled guy has had similar luck, I know that whatever problem is there, it isn't something simple. I may use the shop that I used awhile back to find the leaks in Dwayne's car.....
These shops have more advanced leak detection stuff so maybe they will be able to track it down and get me fixed up.
I do appreciate the efforts put forth by Randy. He gave a few hours of his time and asked nothing in return.
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Here are a few nuggets to chew on. The compressor was doing this:
....The clutch would engage momentarily every 10 seconds or so.
I was told that maybe the high/low pressure switch could be messed up so....
Jumper wire to the CAA white wire plug....
Now the compressor clutch is engaged but the engine bogs a bit from the load. The air starts to blow cold inside, then gets almost as cold as a new car!
But....
The compressor starts knocking like a lawn mower with no oil in it. The pressures seem low for 88 degrees in the shop according to this scale:
But they are in line with what the guy at Classic Auto Air said....I'm pretty sure he said the low side needs to be no lower than 17 and generally around 20-25.
I'm going to call him tomorrow and see what advice that he may have.
....The clutch would engage momentarily every 10 seconds or so.
I was told that maybe the high/low pressure switch could be messed up so....
Jumper wire to the CAA white wire plug....
Now the compressor clutch is engaged but the engine bogs a bit from the load. The air starts to blow cold inside, then gets almost as cold as a new car!
But....
The compressor starts knocking like a lawn mower with no oil in it. The pressures seem low for 88 degrees in the shop according to this scale:
But they are in line with what the guy at Classic Auto Air said....I'm pretty sure he said the low side needs to be no lower than 17 and generally around 20-25.
I'm going to call him tomorrow and see what advice that he may have.
The high pressure side reads real low compared to the chart. What are CAA specs for the high side?
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I'll find out tomorrow. Their guy, Dwight, always seems eager to help.
I remember Dwight from years ago when I was installing the CAA in the Coronet. He was a tremendous help, and patient with my have-no-idea-what-I'm-doing questions.
KD - since you mention your compressor cycling on and off, I did some digging online. I came across another thread where a guy was having the same problem you describe with a CAA system. Classic Auto Air had him change the thermostat 3 different times, but he kept getting the same issue. He finally decided to buy a solid state programmable thermostat and it solved his issue.
The system came with a thermostat as you describe but it did not work out of the box. CAA sent a new thermostat but it did the same thing. ( cycled on/off every few sec)
So I purchased a solid state electronic heat/AC thermostat with a digital readout for temp and installed it. I set the output for 34 degrees off and 46 degrees on which controls the compressor.
The AC works great and I am in the process of refining the system operation.
Classic Auto Air cycling too often
The system came with a thermostat as you describe but it did not work out of the box. CAA sent a new thermostat but it did the same thing. ( cycled on/off every few sec)
So I purchased a solid state electronic heat/AC thermostat with a digital readout for temp and installed it. I set the output for 34 degrees off and 46 degrees on which controls the compressor.
The AC works great and I am in the process of refining the system operation.
Classic Auto Air cycling too often
ckessel
Well-Known Member
Interesting read. I wonder where the guy sourced the programmable t-stat from. Since I'm not there yet on the cars, it would be worthwhile to have that in my info stash for when the time comes.
Not sure which adjustable A/C t-stat that guy used, but Vintage Air offers one that has good reviews on Summit:
Vintage Air 24675-VUT Vintage Air Adjustable Fan Thermostat Kits | Summit Racing
it didn't say in the thread.
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I just spoke with Dwight from Classic Auto Air.
It is common for people to service these systems like they would a traditional A/C system but he said that their system is slightly different.
Because I am not trained or skilled with A/C systems, I am relying on help from others.
Here is where the differences are.
First up, he said that the CAA system needs exactly 24 ounces of refrigerant. Adding more does not make the unit blow colder and could make it blow less cold.
Secondly, he had this rough guideline: The high side number should be approximately 100 plus the ambient air temperature. Yesterday, it was around 87-88 in the shop so the approx number on the high side should be around 188. The low side is supposed to be about 10% of that, or 18-19 psi.
Since I don't know much about this, I have to go by the advice of others.
He also said that many R-134 systems use an Orifice Tube but the CAA units do not. He thinks the charts and graphs commonly published are for systems using the orifice tube style design and that the CAA systems will read lower when they are operating properly.
Dwight said that the knocking in the compressor could be from having more Freon in the system than the 24 ounces they state. He thought the knocking could be from the compressor trying to compress liquid.
He was stumped at first as to why "jumping" the high-low switch wiring allowed the compressor clutch to stay engaged. He later guessed that maybe it is bad and worth changing. There is NO Schrader valve below the switch so replacing it will blow Freon everywhere. I'll buy a switch locally and let the shop change it when they evacuate the system tomorrow.
Like many of you, I'm not one that is content just letting a shop do the work on my car. I want to know why something went wrong or what errors that I made.
More to follow....
It is common for people to service these systems like they would a traditional A/C system but he said that their system is slightly different.
Because I am not trained or skilled with A/C systems, I am relying on help from others.
Here is where the differences are.
First up, he said that the CAA system needs exactly 24 ounces of refrigerant. Adding more does not make the unit blow colder and could make it blow less cold.
Secondly, he had this rough guideline: The high side number should be approximately 100 plus the ambient air temperature. Yesterday, it was around 87-88 in the shop so the approx number on the high side should be around 188. The low side is supposed to be about 10% of that, or 18-19 psi.
Since I don't know much about this, I have to go by the advice of others.
He also said that many R-134 systems use an Orifice Tube but the CAA units do not. He thinks the charts and graphs commonly published are for systems using the orifice tube style design and that the CAA systems will read lower when they are operating properly.
Dwight said that the knocking in the compressor could be from having more Freon in the system than the 24 ounces they state. He thought the knocking could be from the compressor trying to compress liquid.
He was stumped at first as to why "jumping" the high-low switch wiring allowed the compressor clutch to stay engaged. He later guessed that maybe it is bad and worth changing. There is NO Schrader valve below the switch so replacing it will blow Freon everywhere. I'll buy a switch locally and let the shop change it when they evacuate the system tomorrow.
Like many of you, I'm not one that is content just letting a shop do the work on my car. I want to know why something went wrong or what errors that I made.
More to follow....
Last edited:
good info Greg. I have also read elsewhere that overcharging a system can result in warmer air (as stated above).
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There could be a few things going on. I had charged this once myself and 3 times by others and it still isn’t right. I can’t blame anyone but myself. I must have made a mistake on the installation. Maybe an O ring has a slight tear or something. When I did the system on Dwayne's car:
....the installation looked clean and orderly but I had two leaks in areas that seemed to be done right. I'm human, I made mistakes there and probably did with mine too.
This is what some call a "teachable moment" or in other words, an opportunity to learn.
It can be embarrassing to make mistakes for others to see but for many of us, that is how we learn. We make these mistakes and hopefully learn from them. I know that I try to learn. The more experience you have, the better chance you'll have to avoid mistakes or know why they happened and how to correct them. A few things to ponder....
I was surprised to learn that it can hold a vacuum but still leak.
The fact that the compressor bogs this engine down surprised me too. A 495 cube engine shouldn't bog when the A/C compressor is working considering a similar sized compressor is on my daily driver cars with smaller engines. What could be causing that?
....the installation looked clean and orderly but I had two leaks in areas that seemed to be done right. I'm human, I made mistakes there and probably did with mine too.
This is what some call a "teachable moment" or in other words, an opportunity to learn.
It can be embarrassing to make mistakes for others to see but for many of us, that is how we learn. We make these mistakes and hopefully learn from them. I know that I try to learn. The more experience you have, the better chance you'll have to avoid mistakes or know why they happened and how to correct them. A few things to ponder....
I was surprised to learn that it can hold a vacuum but still leak.
The fact that the compressor bogs this engine down surprised me too. A 495 cube engine shouldn't bog when the A/C compressor is working considering a similar sized compressor is on my daily driver cars with smaller engines. What could be causing that?
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I bought another high-low pressure switch and an adapter…
The brass adapter has a Schrader valve in it.
This will allow me to change the switch if necessary without opening the system and losing all the Freon.
It stacks up a bit longer than the one in the car.
It looks like the switch plug will be crowded. With the system open anyway, they could clock that #6 aluminum switch port line a few degrees to aim the switch up a little.
The brass adapter has a Schrader valve in it.
This will allow me to change the switch if necessary without opening the system and losing all the Freon.
It stacks up a bit longer than the one in the car.
It looks like the switch plug will be crowded. With the system open anyway, they could clock that #6 aluminum switch port line a few degrees to aim the switch up a little.
Interesting information. The tech line at vintage air told me to ignore everything but the low side pressure and the vent's temperature.
The rule of thumb he gave me was low side pressure between 12 and 20 and vent temperatures near 40F
I believe I have more than the recommended 1.8lbs of R134 in my system. The center vents are blowing 44F on a low 90s day. One item to note is you need a fan blowing on the grill or condenser while charging the system.
My mechanic friend who charged my system has mentioned nightmares with orifice replacement parts. I'm ignorant about AC systems, but they way he was talking sometimes you go through several orifice replacement parts before getting the system repaired.
Keep us updated on what you learn.
The rule of thumb he gave me was low side pressure between 12 and 20 and vent temperatures near 40F
I believe I have more than the recommended 1.8lbs of R134 in my system. The center vents are blowing 44F on a low 90s day. One item to note is you need a fan blowing on the grill or condenser while charging the system.
My mechanic friend who charged my system has mentioned nightmares with orifice replacement parts. I'm ignorant about AC systems, but they way he was talking sometimes you go through several orifice replacement parts before getting the system repaired.
Keep us updated on what you learn.
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It gets weirder.
I just fired up the car to warm it up. Yesterday I posted the video where the compressor clutch wouldn’t stay engaged. I put in a jumper wire to the hi-low switch plug and the compressor clutch engaged. The air blew cool then COLD.
But…. The compressor knocked and seemed to bog the engine a bit like it was struggling. I was worried that continued running like that would damage the compressor so I shut off the A/C. The engine ran fine and the knocking from the compressor stopped. Todays talk with Dwight had me thinking that the knocking could be from having too much Freon in the system, at least more than Classic Auto Air suggests.
Okay…..
I start it up and press the slider to engage the A/C and guess what?
It worked. The air blows as cold as you’d expect. The compressor clutch engaged as it should and didn’t knock.
Have you ever “fixed” something and didn’t know what you did? It is puzzling.
The gauges read different from yesterday…
This was before I started it. Randy told me at rest, the numbers should read equal.
Confession: Yesterday I made a mistake with the gauges. There are knobs at the end of the red (high side) and blue (low side) couplers. The knobs are to be turned CCW to remove or attach the couplers to the A/C ports, then turned CW to effectively seal and open the valves in the ports. I didn’t have the knobs turned all the way clockwise. I reported a false reading.
Here it was during the first few minutes.
It then dropped the low side to be within CAA specs while the high side climbed.
Todays temperature:
Then the high side got higher.
Then higher.
CAA stated that the guideline is 100 plus ambient. Online sources state double the ambient temperature so both show that I should be under 200.
How much is too much ?
It is blowing quite cold and not knocking so what the heck happened???
I just fired up the car to warm it up. Yesterday I posted the video where the compressor clutch wouldn’t stay engaged. I put in a jumper wire to the hi-low switch plug and the compressor clutch engaged. The air blew cool then COLD.
But…. The compressor knocked and seemed to bog the engine a bit like it was struggling. I was worried that continued running like that would damage the compressor so I shut off the A/C. The engine ran fine and the knocking from the compressor stopped. Todays talk with Dwight had me thinking that the knocking could be from having too much Freon in the system, at least more than Classic Auto Air suggests.
Okay…..
I start it up and press the slider to engage the A/C and guess what?
It worked. The air blows as cold as you’d expect. The compressor clutch engaged as it should and didn’t knock.
Have you ever “fixed” something and didn’t know what you did? It is puzzling.
The gauges read different from yesterday…
This was before I started it. Randy told me at rest, the numbers should read equal.
Confession: Yesterday I made a mistake with the gauges. There are knobs at the end of the red (high side) and blue (low side) couplers. The knobs are to be turned CCW to remove or attach the couplers to the A/C ports, then turned CW to effectively seal and open the valves in the ports. I didn’t have the knobs turned all the way clockwise. I reported a false reading.
Here it was during the first few minutes.
It then dropped the low side to be within CAA specs while the high side climbed.
Todays temperature:
Then the high side got higher.
Then higher.
CAA stated that the guideline is 100 plus ambient. Online sources state double the ambient temperature so both show that I should be under 200.
How much is too much ?
It is blowing quite cold and not knocking so what the heck happened???
Almost exactly the high side number this chart wants...
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Holy crap.
I was worried that the compressor would crap out. If it is working and not knocking or puking fluids, I’m happy.
I would like to know what happened between yesterday and today. I strongly suspect that nobody came here to fix it while I was asleep.
The compressor clutch wouldn’t engage and now it does.
The compressor knocked some but now it doesn’t. It does squeal a little but only around 1800-1900 rpms.
I was worried that the compressor would crap out. If it is working and not knocking or puking fluids, I’m happy.
I would like to know what happened between yesterday and today. I strongly suspect that nobody came here to fix it while I was asleep.
The compressor clutch wouldn’t engage and now it does.
The compressor knocked some but now it doesn’t. It does squeal a little but only around 1800-1900 rpms.
Last edited:
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