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. :rolleyes:

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]

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]

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.

[TXRaceFan]

"

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.

Thanks Rick. I need to look more closely at it. All this was set up and worked when I got the car and now that I'm tinkering and tweaking I realize I really need to look into all these kinds of things and how they are wired. I'm sure it's got a relay but haven't traced it to see where it is and whether I have the other switch you mention. I'll bet it does but need to be sure. Do most use the temp switch as well with this type of system?

[TXRaceFan]

I've confirmed it has a binary switch installed under the dash.

The thermostatic switch is wired into the trigger circuit of a relay driving a SPAL fan. The only thing suspect was this was direct to the hot and not through the ignition "on". I'm ok with that except it allowed the thing to run the battery down when the switch acted up.

I looked at the VA site and the temp probe they use is wired to the relay ground where my probe has a heavy-ish wire (capillary tube?) to and adjustable rotary switch and controls the triggering.

Can't find anything wrong with how it is working. Turns off and on fine and will set to come on at 190 or so.

Is there anything to know about that prob and its line? Can it be bent too sharply or ground out or anything? When I got the car it was all spiralled and mounted in front of the core support for the whole world to see and I ran it more discretely behind the battery and straightened some of it and it's definitely touching the body/frame in a few places. I don't think I kinked it anywhere.

[Rick_L]

The thermostat switch is on the evaporator case inside the passenger compartment.

The binary switch is usually screwed into the drier or close to it.

The trinary switch just replaces the trinary switch.

If you go to the Vintage Air site, in the lower left corner of the home page is a paragraph called "Basics". There is a link to .pdf file. In the .pdf is a description of the binary switch, trinary switch, thermostat switch, their locations and how they are wired. What they show is the right way to do it.

http://www.vintageair.com/AC%20Basics/AC%20BASICS%20%206%2029%2009.pdf

[TXRaceFan]

I think I've got it.

Downstream of the drier is hard line into the firewall and right inside prior to the expansion valve is the binary switch. It is tight up there but I'm 99% sure the blue wire off it is coming back into the engine compartment and directly to the compressor. These instructions (page 15) shows the binary safety switch just that way:

http://www.vintageair.com/DownloadsSection/Surefit/Chevrolet%20Passenger%20Cars/1957%20Chevrolet%20Passenger%20(Cable-operated)%20(Inet).pdf

I can see the evaporator thermostat switch also under the dash there but I can't see the capillary tube or the wires although I'm sure that is what it is.

The fan operates independently and also uses a thermostatic type switch with a capillary tube that runs to the drain plug of the radiator. I think I must have created a glitch when I moved this switch trying to clean up the routing when putting on the power steering. Had to remove the radiator to replace the crank pulley, etc. Just not sure what the glitch is other than something related to the capillary tube.

Thanks.

[Rick_L]

"This means your fan won't have to run all the time (and wear out that much sooner)."

From my earlier post.

Again, I'm not a believer in running the fan when you don't have to. Like wiring it to the compressor so that it runs whenever the compressor does.

[acardon]

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.

The fan operates independently and also uses a thermostatic type switch with a capillary tube that runs to the drain plug of the radiator. I think I must have created a glitch when I moved this switch trying to clean up the routing when putting on the power steering. Had to remove the radiator to replace the crank pulley, etc. Just not sure what the glitch is other than something related to the capillary tube.

The capillary tube in the radiator has nothing to do with the A/C. It controls the fan when the A/C is not on. When the A/C is on, the fan probably runs all the time without a trinary switch. If the engine runs at 190 without the air, the capillary tube is working OK.

[Rick_L]

There is a capillary tube on the thermostat switch in the evaporator - but it's entirely different and separate from the one you're using to switch the fan based on coolant temperature.

Point is, you need both coolant temperature and a/c high pressure to control the fan.

[TXRaceFan]

The capillary tube in the radiator has nothing to do with the A/C. It controls the fan when the A/C is not on. When the A/C is on, the fan probably runs all the time without a trinary switch. If the engine runs at 190 without the air, the capillary tube is working OK.

Not sure who suggested the cap tube in the radiator has anything to do with the a/c. The fan does not run all the time when the a/c is on. It's totally independent of the a/c runs when the coolant temp is above x temp.

Rick, seems like to me, even without a trinary switch it should still work ok as long as it properly comes on when the coolant temp exceeds the set point of the fan thermoswitch (which to me should be near preferred operating temp of the car ie. 190). If the a/c pressures get out of bounds, the binary switch will cut the whole thing off. To avoid overrunning the fan, the way it's set up, it should be wired into the ignition "on" and then it will shut down when the car is cut off.

Maybe I don't get it but I'm ok with it kicking on when the coolant gets above a certain temp vs a/c pressures deciding it, provided it comes on prior to the system pressures getting too high. Are you saying the car can run at 190 but the condensor temp will be significantly higher necessitating the fan be on for proper operation of the a/c? If so, there's surely some way to determine the proper temp set point for the fan to come on at that pressure condition.

Anyway, the trinary sounds like the right solution. Does the system have to be "cracked open" to switch from a binary to trinary switch or is it switchable with minimal loss? If it must be opened up, I'm disinclined to mess with it at this point and try and manage it the way it was originally set up even at the risk of running the fan more often than necessary.

Thank you all for your insight.

[acardon]

Not sure who suggested the cap tube in the radiator has anything to do with the a/c. The fan does not run all the time when the a/c is on.

Sorry, I missunderstood. You mentioned a "glitch" in the cap tube and I thought you thorght it had to do with the A/C problem. :)
Yes, you do have to drain the system to install the trinary.
A trinary switch is probably a good idea, but Vintage Air and Classic Auto Air both send a binary switch with their systems, but they recommend that the fan run all the time the A/C is on.

[TXRaceFan]

No sweat. I always appreciate your quick responses Don. You, Rick, and many of the others have helped me a ton since I got this car and I'm very grateful.

I've been a member of many of boards (Camaro, Chevelle, Powerstroke, etc) over the years and the membership of this one are the most helpful and knowledgeable of them all.

You guys are the best. :congrats:

[Rick_L]

"Maybe I don't get it but I'm ok with it kicking on when the coolant gets above a certain temp vs a/c pressures deciding it, provided it comes on prior to the system pressures getting too high. Are you saying the car can run at 190 but the condensor temp will be significantly higher necessitating the fan be on for proper operation of the a/c? If so, there's surely some way to determine the proper temp set point for the fan to come on at that pressure condition."

It is quite possible for the engine coolant temperature to be under control, and not running the fan - and when this happens it's quite possible the a/c system won't be cooling properly because of high head pressure. In other words this is not a matter of system protection, but a matter a/c performance.

"but they recommend that the fan run all the time the A/C is on."

I don't think you'll ever see that said directly. The reason not to use a trinary switch is if you have a mechanical fan.

[hotrodg726]

when I put a/c in a customers car I always ad a realy to the fan so it comes on when the a/c is turned on. I also have the fan connected to a thermostat so the engine coolant will bring it on when not using the a/c . the condenser must have suffecient airflow at all times to work properly . Most of the aftermarket systems I have installed ask for the fan to be on when the a/c is turned on .

[TXRaceFan]

It's got a mechanical metal flex fan without a shroud and the SPAL pusher in front of the condensor set to run on thermostat.

I may hook it into the compressor + to come on when the a/c is running although fact of the matter is in the Houston summer, it will almost always be running in stop and go traffic regardless of a/c on or not. The lack of shroud is not a great situation. That's the way it was when I got it. It's pretty tight in there with the radiator in front of the core support.

I'd do the trinary switch if I could do it without having to open the system up. Had we had all this discussion and I knew it only had .2# in it I might have done it then.

Thanks.