Help with AC system

[redgum78]

I have had my Charger for 10 years now and the AC has never worked.
All components looked in reasonable order so I had a new receiver dryer fitted and the AC gassed up a few weeks ago.

It blows coolish air- around 65degrees F when ambient is 90degrees. Everything seems to function ok, hot compressor discharge, warm on the condenser outlet, feels cold across the TX valve and on the return to the compressor.

Should the vent air get cooler than 65 on a hot day or am I asking too much of a system that's nearly 50 years old?

[Gold Rush]

I've always been told a 40 degree difference between ambient air and output temps was a good performing a/c system.  Here is some light reading that you might find interesting..

https://mechanics.stackexchange.com/questions/31874/what-temperature-should-the-a-c-blow

[b5blue]

Interesting read. My car had A/C but most parts and condition had me gut the dash and install a Classic Air system. What did you charge the system with?

[redgum78]

Thanks for the reply's, I am well short of 40 degrees lower than ambient. The AC guy used R134a, He added dye so any leaks should be fairly apparent. So far it seems to be holding pressure. I think the AC circuit is working reasonably well but I am not convinced my blower fan is passing much air through the evaporator. I have good flow out the vents but with all the vacuum doors and such it seems pretty difficult to confirm the air is actually passing through the evaporator.

Anyone know of an easy test to ensure the blower air is going the through the evaporator (other than pulling it apart)?

[green69rt]

As an amateur, I have done several auto AC systems and in my opinion you really need to get a set of gauges to diagnose problems.  You'l need them later to work on the system so not wasted.  With the gauges you'll be able to tell if the compressor is working properly, otherwise you're just guessing.  Did the guy that charged the system tell you what the readings were and say all is ok?  Did he add oil to the system during the charge?

Since you put in a new dryer the next cheapest place to look is the expansion valve.  Where is NHcharger when you need him?

[redgum78]

As an amateur, I have done several auto AC systems and in my opinion you really need to get a set of gauges to diagnose problems.  You'l need them later to work on the system so not wasted.  With the gauges you'll be able to tell if the compressor is working properly, otherwise you're just guessing.  Did the guy that charged the system tell you what the readings were and say all is ok?  Did he add oil to the system during the charge?

Since you put in a new dryer the next cheapest place to look is the expansion valve.  Where is NHcharger when you need him?

I think I might do just that, this is my only classic car with AC but both of my daily drivers have AC, at some stage they will need work so I can justify getting gauges I think. Yes he did add oil but he did not mention the pressures in the system.

[Bronzedodge]

Oh boy.  Is this the original RV2 compressor?  They tend to leak at the shaft seal if it isn't new-ish.  Is you heater valve leaking through?  I had a problem with a slipping cable a while back, which prevented the valve from closing - thus reheating the cooled air.

Ambient temperature, humidity all affect the load the evaporator sees.  R134a is NOT compatible with the original mineral oil in the system.  Ester oil is better in a 134 conversion than PAG oil.  A FSM is your friend.

[cdr]

The water valve on the firewall is probably not shutting off all the way, close off the heater hoses & see how cold it gets, mine blows SNOWBALLS even when its 110outside

[redgum78]

We have just got back from a 1000m round trip and I run the AC for most of it. It helped cool the cabin some but it was not near as cold as I would have liked. I think a lot of the problem is lack of insulation on the firewall and the trans tunnel. I drive barefoot on long trips so I really noticed just how much heat enters the cabin from the trans tunnel and firewall as my feet were getting pretty warm! I could feel it through the carpet.

Yep, original compressor and I would be surprised if it wasn't leaking some. The AC guy I used has a ton of old cars himself so I think it would be pretty well across oil's and their compatibility (I will ask him though).

Yep heater tap does pass a little- I generally leave it clamped all year round as I don't use the heater.

Thinking I might dynomat the fire wall and tunnel and if the AC system leaks down over time I might upgrade to one of the newer AC systems.



Dan

[b5blue]

  Dan I know what you mean I drove my car for 2 years with no carpet. Common matting won't block heat much if any. I tested with a laser pointed heat gun and got an honest 15 degree shielding from this foil/fiberglass mat: https:  https://www.amazon.com/Thermo-Tec-13575-Adhesive-Aluminized-Barrier/dp/B00029KC2K/ref=sr_1_19?dchild=1&keywords=thermal+insulation&link_code=qs&qid=1584282814&sourceid=Mozilla-search&sr=8-19
  On the tunnel I used a second layer with bubble foil as it won't get foot pressure that would flatten it. If you figure 6 inches to each side of the exhaust pipes to the mufflers for the foil/fiberglass matting it's effective. I tested and drove here in Florida where the heat is brutal. You can find the same type matting from other sellers on amazon and eBay the trick is breaking solid contact for heat to conduct through in the hottest areas.

[redgum78]

  Dan I know what you mean I drove my car for 2 years with no carpet. Common matting won't block heat much if any. I tested with a laser pointed heat gun and got an honest 15 degree shielding from this foil/fiberglass mat: https:  https://www.amazon.com/Thermo-Tec-13575-Adhesive-Aluminized-Barrier/dp/B00029KC2K/ref=sr_1_19?dchild=1&keywords=thermal+insulation&link_code=qs&qid=1584282814&sourceid=Mozilla-search&sr=8-19
  On the tunnel I used a second layer with bubble foil as it won't get foot pressure that would flatten it. If you figure 6 inches to each side of the exhaust pipes to the mufflers for the foil/fiberglass matting it's effective. I tested and drove here in Florida where the heat is brutal. You can find the same type matting from other sellers on amazon and eBay the trick is breaking solid contact for heat to conduct through in the hottest areas.

Thanks b5, I will look into that matting. Did you notice an improvement in road noise after fitting it?

[cdr]

Having the correct amount of freon is very critical

[b5blue]

  Dan I know what you mean I drove my car for 2 years with no carpet. Common matting won't block heat much if any. I tested with a laser pointed heat gun and got an honest 15 degree shielding from this foil/fiberglass mat: https:  https://www.amazon.com/Thermo-Tec-13575-Adhesive-Aluminized-Barrier/dp/B00029KC2K/ref=sr_1_19?dchild=1&keywords=thermal+insulation&link_code=qs&qid=1584282814&sourceid=Mozilla-search&sr=8-19
  On the tunnel I used a second layer with bubble foil as it won't get foot pressure that would flatten it. If you figure 6 inches to each side of the exhaust pipes to the mufflers for the foil/fiberglass matting it's effective. I tested and drove here in Florida where the heat is brutal. You can find the same type matting from other sellers on amazon and eBay the trick is breaking solid contact for heat to conduct through in the hottest areas.

Thanks b5, I will look into that matting. Did you notice an improvement in road noise after fitting it?

I used strips or squares of something like Dynamat to deaden some sound but didn't go nuts, the fiberglass mat is very sticky so I guess it helped also.

[Bronzedodge]

We have just got back from a 1000m round trip and I run the AC for most of it. It helped cool the cabin some but it was not near as cold as I would have liked. I think a lot of the problem is lack of insulation on the firewall and the trans tunnel.

It is not an insulation problem.  There is no reason it shouldn't work properly, unless something is wrong.  Undercharged, overcharged is just as bad.  Leaking shaft seal, bad EPR valve, bad TXV.  Mineral oil used with R134a instead of Ester oil.  All will cause high discharge air and lack of capacity.  The 134a charge is about 80% or an R-12 charge, but the delta T should be checked at 1500-2200 rpm on a hot day.  The procedures in the FSM with respect to the humidity are good.   I was amazed at how dirty the condenser inlet was on my 69.