A/c

[rittenrotton 4]

So my a/c seems to work great on 70 degree days but recently here in NY its been 87 and very humid and I'm finding that my a/c seems to not work so well with these recent temps (especially on a sunny day). I have a 70 coupe with a ford racing 302, with a flex fan and classic auto air. To just keep the car a little cool, I have to keep the a/c on high even when driving on a highway. I am just wondering, is wrong to think that aftermarket a/c kits would work as well as modern a/c in a newer car?

[Rsanter 152]

Seems like your system needs service. Possible low on refrigerant.

 

Bob

[Tcoco 5]

mine is the same way brand new system but my theory is I have a black vinyl top and no insulation only thing up there is metal and a thin headliner so my head is warm but my lower half is cool I'm waiting on mustangs to fear   to finish the one piece headliner I would have hoped it would be ready now so I can insulate the roof

[danno 128]

If your car used to cool adequately and now is not, it is one of a couple things.  You could be low on Freon, you could have heat from the engine circulating in the heater core. Something you can do to verify is to take two of a 1/2 inch bolt and use it to plug up the heater lines so you get no chance of hot water circulating in the heater core.  All those factory water valves leak water, so you get some hot water circulating through the heater core.  This entirely defeats the purpose of the AC.   

 

I put a water valve like you see in your water pipes at home on my hot water lines to the heater core.  I shut it off from June 1 to Sept 1 so I can be completely sure there is no hot water in the heater core.

 

You have a Freon line from the evaporator coil under your dash to the compressor.  If it is getting cold or cool half way between the evaporator and the compressor, the odds are you are not low  on Freon.  If it does not get cold where it leaves the evaporator and goes through the firewall, the odds are you are low on Freon.

[barnett468 418]

ok.

 

put the ac on high and stick a thermometer around 1" into an ac vent and drive the car at 30 mph or more for 5 minutes then remove the thermometer while still driving and tell us what it says and what the outdoor temp is.

 

with the car parked and ac on, raise the engine rpm to a very high idle like almost 2000 rpm for 60 seconds then look at the hoses on the compressor . one should have frost on it . grab the hoses and one should feel as cold as an ice cube . if it is not either of these, your system has a problem.

 

if your car ever runs more than around 7 degrees above what the thermostat is rated at, your cooling systems is insufficient [it sucks].

[1969_Mach1 333]

Might be low on refrigerant would be my first guess.  Since you probably don't have a leak detector look closely at all the hose connections.  Any oily residue at a fitting/connection is a sure sigh of a leak.  Like barnett468 mentioned, on a fully charged system the line from the evaporator (at the firewall ) back to the compressor should be cold, 45 deg or so near the firewall.  Sometimes, but not often will you see frost on R134a systems compared to older R12 systems.  Since it is not the stock system, it probably uses a bend door to stop air flow through the heater core when the A/C is on.  That could be leaking.  I think it Is an expansion valve type of system.  In which case the expansion could be stuck closed or mostly closed.  But again, low refrigerant charge is my first guess.

 

By the way, operating the A/C on the max setting, not max fan speed, provides the least load on the compressor.  On "max A/C the blend doors are positioned to recirculate the air inside the car.  So with each pass the air is a little cooler and a little cooler resulting in less heat load on the system.  On normal A/C outside air is brought into the car.  So the A/C is constantly trying to cool outdoor air.  

[barnett468 418]

i have my own ac machine and i made frost on every single stock system i put r134 in and many of the aftermarket units that use r134.

[1969_Mach1 333]

Congradulations!

[rittenrotton 4]

Thank you for all your help! I spoke to Classic Auto Air an they said something is definitely wrong with my AC. They say it could be low refrigerant or that the condenser might be clogged? Either way I am going to have to take it somewhere to get serviced. Either way its a little over my skill level to solve/fix. I'll keep you all updated and thanks again!