Need aftermarket a/c advice

[TXRaceFan]

When I bought my 57 it had aftermarket a/c already installed. Best I can tell from the vent style it's a Vintage Air unit.

What I can't figure out is it has some type of switch with a dial on it mounted under the passenger side of the dash out of sight but within adjustment reach. It is definitely an aftermarket type of switch and I believe associated with the a/c.

I'm not sure what it does and couldn't determine from the installation instructions. Had the car out for a cruise today and it wasn't cooling as well as I'd hoped although it feels 150 degrees and humid out. Car ran a steady 190 and has an electric fan in addition to the mechanical fan. It's cool but not icy like I'd expect. I'm assuming the charge is correct as it blew cold during the winter. Now that the system is taxed, I wonder if there is some adjustment.

I did learn that my "interior / exterior" are mismarked and all the handles should be in the top position to maximize cooling. Just wondering if this other switch affects something to allow for the max cool mode. Perhaps it stops flow the the heater core?

Maybe I have an evaporative unit in the car - once I worked up a sweat, the blower felt ok.

Any ideas?

[hotrodg726]

typicly that separate knob is the thermostat for the a/c crawl under the dash and check it out . adjusting it will help your a/c if it is the thermostat . good luck

[acardon]

I agree, it probably is a thermostat. A thermostat cuts the compressor clutch off when the temperature across the evaporator core gets low enough for it to start freezing up. If the thermostat is set too high, you will notice that the compressor stops running before it gets cold enough. If the compressor is not shutting off, the thermostat is not keeping it from getting cold enough.
Just because it cools good in the winter doesn't mean it's charged sufficiently to cool in the summer when the outside temperature is 30 degrees hotter. A pressure test is the only way to know if it's charged correctly or if there is another problem.

[TXRaceFan]

Originally Posted by acardon

Just because it cools good in the winter doesn't mean it's charged sufficiently to cool in the summer when the outside temperature is 30 degrees hotter. A pressure test is the only way to know if it's charged correctly or if there is another problem.

I was afraid of that. Last August it seemed to be ok although the volume of air this thing moves is kind of lame. I guess I'm just used to my pickup freezing your behind off in 10 seconds on high.

I found something in the Troubleshooting section of the Vintage Air site and it suggests you can't have the thermostat set all the way to the right. I'll back it down the recommended 1/8 turn and give it another shot before I look at the pressures.

I have some gauges from the R12 days. Do they make adapters that will let me connect my gauges to the 134 system?

[Old Buzzard]

Electric and mech fan... Is the elect fan on the ft of the a/c condensor?? If so, the motor can be blocking a considerable amt of the core...

[Rick_L]

I don't think VA has changed their instructions - mine say the thermostat should be all the way clockwise unless the unit is freezing up even with a proper charge, then back off only slightly.

A properly installed and charged VA unit will freeze you out just like your pickup.

If you have a mechanical fan, this may not happen unless the car is moving.

[TXRaceFan]

Originally Posted by Old Buzzard

Electric and mech fan... Is the elect fan on the ft of the a/c condensor?? If so, the motor can be blocking a considerable amt of the core...

Electric fan is in front of the condensor. Car has run perfectly cool until this afternoon's hour-long cruise. It climbed to about 210 at a couple of stoplights and never returned all the way to 190. Kinda wierd. I may have not gotten it purged of all the air when I had the radiator out recently.

Sounds like I need to have the freon level checked.

[TXRaceFan]

Well I found out a couple of things. Thermostat switch on the electric fan is acting up. Has worked perfect until now. The thing ran forever when I got home and ran the battery down on the car. It kicked off when cruising on Monday which is why it got so hot.

Had Jr. take the car in yesterday and it only had .2# of freon in it. While it was in (and I was at work) I found the charging instructions on the VA site and it said the suction pressures were much lower than normal 134a due to it having an expansion valve. Fortunately it also had the precise amount of freon required and I was able to get the info to them before he tried to charge it based on an incorrect suction pressure. Curious as to how it could be so low (assuming properly charged initially) - they said they did a leak test and found nothing. Any ideas on that?

Now to look at the fan. I may jet the thermostat.

Question (for summer driving): 1) wire it to the a/c so it comes on with a/c ? or 2) wire it on when the car is running?

[acardon]

Do you have a relay in the electric fan circuit? The temperature switches are not designed to carry the load of an electric fan.

[Rick_L]

"Question (for summer driving): 1) wire it to the a/c so it comes on with a/c ? or 2) wire it on when the car is running?"

The proper way to wire the fan for a/c use is to use a trinary switch from Vintage Air. It now probably has a binary switch which will cut off the compressor if the pressure is 1) too low or 2) too high. These are for system safety. The trinary switch has a third function which runs the fan when the high side pressure goes over a set point. Usually this means your fan will run when idling or driving at slow speed, and turns off when driving at higher speed. This means your fan won't have to run all the time (and wear out that much sooner). You can wire this into the same relay as the coolant temperature switch.