AC problems are making me HOT!
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AC problems are making me HOT!
Posted: May 27 2007 02:40 PM
 
Brady McQueen (aka 1carguy) [ View ] [ bradymcqueen@comcast.net ] [ Car Ads ] [ Blogs ]
Pleasanton, California
(925) 719-3200
 
I'm down to the last item on my 37...the AC. I found that the builder left a hose connection loose at the evaporator so I replaced the oring, evacuated the system, and recharged it. It works great, gets real cold for maybe 5 minutes or so, then starts getting warmer and then the compressor starts getting noisey and seizes up. It gets bad enough the belt starts slipping and nearly stalls the motor. If I let the car sit for half an hour or so and restart it, the air works fine, the compressor is quiet but the problem comes back after maybe 5-10 minutes of running. It's a new Vintage Air Compac Gen II system with a chrome compressor from S&Performance. If the compressor was toasted, why would it work fine (no noise) for the first few minutes? Could it be building up too much pressure or heat after running? It's a 134 system that calls for 1.8 lbs of freon and we put in about 2.5 12oz cans. I'm stumped. Any ideas? Maybe I'll call Vintage Air tech line.
 
 
Comments
 
Posted by Crazyhorse Rod Shop  -  05/27/2007 02:44 PM
should have a binary switch to shut down if low or high ( usualy on dryer ). may be overcharged.
dont poke the porchdog........he bites [ View ] [ Email ] [ Blogs ] [ Car Ads ] BLUFF DALE, Texas Charter Member since March 2003
 
Posted by 1carguy  -  05/27/2007 03:32 PM
Hey Shine...guess what?? there's no binary switch in the system at all! I just read the Vintage air paperwork and they strongly recommend installing the OPTIONAL cycling switch, but mine doesn't have one. My son has quite a bit of experience with ACs and he noticed that the electonically controlled radiator fan did not automatically come on when the AC was turned on. He said that especially with a 134a system the condenser will get really hot without air flow and will drive the temps/pressures off the map in no time. We let the car run long enough for the fan to turn on and guess what....AC worked fine while the fan was running. So maybe the system wasn't wired right for the fan to come when the AC is turned on. He thinks it's controlled by the ECU. That could be a nightmare trying to trace that down. I suggested adding a wire from the compressor to the fan but he's afraid it might somehow interfere with the commuter. Damn, I wish I had a carbureted car instead of EFI.
1carguy [ View ] [ Email ] [ Blogs ] [ Car Ads ] Pleasanton, California
 
Posted by da34guy  -  05/27/2007 03:58 PM
Brady- I know how ya feel.

Thats 1 of the reasons the last coupe went bye bye.

Tryed it twice, no more putrs,ecu's, ecm's and all that other ec SH*T. That why the new coupe is a bare bones driver. Don't even have A/C in it. Oh yeah it does -- Both window down and 85 MPH.

Good luck.

Time to sell that fairground cruiser and build a real DRIVER.
Don [ View ] [ Email ] [ Blogs ] [ Car Ads ] Prescott, Arizona Charter Member since October 2001
 
Posted by dixie  -  05/27/2007 04:30 PM
head pressure thats it .you can put a remote switch on fan an turn it on manually when you turn the a/c on. Don't think it will screw up computer. i'm with 34 ant got one to worry about.
jim grace [ View ] [ Email ] [ Blogs ] [ Car Ads ] dade city, Florida Charter Member since January 2006
 
Posted by Crazyhorse Rod Shop  -  05/27/2007 05:00 PM
dont care what system it is it has to have a pressure switch or it will blow up the comp with head pressure. must have a high/low somewhere.
dont poke the porchdog........he bites [ View ] [ Email ] [ Blogs ] [ Car Ads ] BLUFF DALE, Texas Charter Member since March 2003
 
Posted by hotrodgene  -  05/27/2007 05:05 PM
You have exess head pressure due to over charge.
Gene Riffe [ View ] [ Email ] [ Blogs ] [ Car Ads ] Saint Petersburg, Florida
 
Posted by APLUS  -  05/27/2007 11:11 PM
Watch the gauges when your problem is happening and that will tell you exactly what's happening. It does sound as if the pressures are going sky high because of no air flow across the condenser. A trinary switch is recommended when running an electric fan--high pressure (380 psig), low pressure (30 psig) and fan operation (220 psig). This is with a R134a system. Some systems bring the fan on as soon as the compresor is energized. Since you have a computer controlled fan, I believe you will need to get in touch with computer (wiring system) manufacturer you have to see exactly what needs to be checked or changed or someone very familar with ecu systems. Of course no matter who's system or which refrigerant is used it would be highly recommended to have a low and high pressure switch in the system to prevent damage.
APLUS [ View ] [ Email ] [ Blogs ] [ Car Ads ] Austin, Texas
 
Posted by 1carguy  -  05/27/2007 11:10 PM
I did some more checking today and found that the fan is not controlled by the ECU afterall. It's got a regular temp sensor switch that kicks it on at 195 degrees. I just bought a ground relay that I'll wire into the system tomorrow that will turn on the fan anytime the compressor is engaged. Tues I'll order the the pressure switch from Vintage. I can't see where to install this, hope Vintage has an easy solution for this, I'd hate to have to start cutting into or modifying the system. Thanks guys for the input.
1carguy [ View ] [ Email ] [ Blogs ] [ Car Ads ] Pleasanton, California
 
Posted by APLUS  -  05/27/2007 11:49 PM
The drier on my system (Vintage Air) has a place on it to install the trinary or binary switch. If you're going to wire the fan to come on when the compressor is energized, then all you need is the binary switch (high & low) pressure switch. I like the trinary switch because I didn't want the fan running while going down the highway when it's not needed for cooling the water temperature or for air flow across the condenser. The fan only comes on when water temp. rises or the high side a/c pressure rises to 220 psig.
APLUS [ View ] [ Email ] [ Blogs ] [ Car Ads ] Austin, Texas
 
Posted by plwheelie  -  05/28/2007 12:26 AM
II agree with hotrodgene, the system is over charged. There was a good article in last months Street Rodder where they interviewed the different AC mfg's and the main problem ppeople have with installations was over charging with 134 freon. The low side pressure should only be about 20 psi. I reached that pressure with only 1 can of freon and my system cools better now than it ever has. I have had this unit for 7 years with R12 in it, now I converted it to 134 after changing the engine.

Just my experance

Paul
plwheelie [ View ] [ Email ] [ Blogs ] [ Car Ads ] Tahlequah, Oklahoma
 
Posted by APLUS  -  05/28/2007 01:20 AM
Paul, from my experience and using Vintage Air formula for charging their system, 20 psig on the low side would be to high of pressure for a R134a system. VA system runs a low pressure of 6-12 psig. Remember this is a Vintage Air system being charged under the conditions they outline, blower on medium, doors and windows closed, engine running 1500 rpm's and shop fan directly in front of condenser. This formula is for VA R134a systems only. Now I agree that Brady might be about 1ounce overcharged but when it starts off cooling and then started his problem without the fan running that tells me he's running to high of head pressure----then when he says it cools fine when the fan starts running**TA-DA**, the problem, no air flow (fan) across the condenser.
APLUS [ View ] [ Email ] [ Blogs ] [ Car Ads ] Austin, Texas
 
Posted by JAWS  -  05/28/2007 09:57 AM
I am assuming you know that temp switch is a ground for the fan relay. Your compressor wire will be 12 volts. I would install a second relay for the fan and tie it into the lead going to the fan. Don't worry about it affecting the other relay, it wont matter if the other is on powering the fan when the engine gets to temp and turns it on also.


Of course you probably already knew this, I was just checking.....

-Brant
An electrical headache can make a great car a pain [ View ] [ Email ] [ Blogs ] [ Car Ads ] Boise, Idaho Charter Member since August 2004
 
Posted by 1carguy  -  05/28/2007 01:49 PM
Hey, thanks for all the info. I didn't expect so much response from this thread. Ain't this site great?!? I decided not to just wire it so the fan comes on with the AC compressor engaged. That might be just hiding a bigger problem. I think after doing some reseach and considering all your comments, I've probably got a half can too much charge, plus the high pressure needs to be controlled with a pressure switch rather than just relying on the fan to control the pressure by cooling the condenser. After reading about it, looks like a trinary switch (one that controls pressure and fan engagement) is the better way to go than just a binary. Agree? I'll let you all know how this ends up.
1carguy [ View ] [ Email ] [ Blogs ] [ Car Ads ] Pleasanton, California
 
Posted by srodder39  -  05/29/2007 08:06 AM
Vintage air will recommend to charge by weight on their 134 units.
srodder39 [ View ] [ Email ] [ Blogs ] [ Car Ads ] santa fe, Texas
 
Posted by JAWS  -  05/29/2007 04:37 PM
True about the trinary switch. It will kick the fan on any time power is supplied to the compressor from the a/c controls. However if the pressure is not within specs the switch will not send power to the fan or the compressor and it will also not cycle the fan each time the compressor comes off and on. It will keep the fan on as long as the a/c comtrols are on in the mode calling for compressor engagement. Make sure you wire it right....
An electrical headache can make a great car a pain [ View ] [ Email ] [ Blogs ] [ Car Ads ] Boise, Idaho Charter Member since August 2004
 
Posted by fujimo  -  06/08/2007 12:38 PM
good morning to all. I'll try to make this comment more informative than the (CAR)one.I am in the process of hooking my A/C up also.Brady i hope you don't mind me using your disscusion forum. I been looking for the information on how close to installing condenser to radiator.I was also wondering if you hook the trinary switch into your drier . Thanks MIKE
Mike McLain [ View ] [ Email ] [ Blogs ] [ Car Ads ] Duncan, Oklahoma Charter Member since December 2005
 
Posted by Crazyhorse Rod Shop  -  06/08/2007 01:19 PM
1/2 in between and the switch goes in the dryer. i charge 134 by performance . i use a temp gage in the vent. there are many variables to how much. i have yet to use more than 2 cans. 134 will stop cooling when you over charge.
dont poke the porchdog........he bites [ View ] [ Email ] [ Blogs ] [ Car Ads ] BLUFF DALE, Texas Charter Member since March 2003
 
Posted by js  -  06/08/2007 02:11 PM
I would difinately check the pressures. I do residential a/c but I think this should apply here. If the low side is low and the high side is high with the fan on there could be excessive moisture in the system causing the refrigerant device to freeze up. Alot of times the low side will even go into a vacuum. Only adding this because you did say the system had a leak in it. This is just another consideration in case the above fails.
js [ View ] [ Email ] [ Blogs ] [ Car Ads ] college station, Texas
 
Posted by toploader  -  06/08/2007 06:29 PM
to much freon, you put in 2.5, and it called for 1.8, if you put to much freon, it will slug the compressor with liquid, you can't compressor a liquid, put the right amount in it and try again, if it didn't hurt the compressor already.
toploader [ View ] [ Email ] [ Blogs ] [ Car Ads ] Oxon Hill, Maryland
 
Posted by APLUS  -  06/08/2007 11:27 PM
Toploader: Brady had put in 2.5 cans (12oz. cans) of R134a witch equals 30 ounces and Vintage Air calls for 1.8 pounds. If you do the math he's over by 1.2 ounces. That's why I said earlier he could be overcharged by roughly one ounce but if he purged the hose of air he could of been right on the money. Even if the system was overcharged by 1.2 ounces I don't believe it would of slugged the compressor. It's hard to diagnose over long distance but I still believe it was the lack of air flow across the condenser causing his problem. Disconnect the condenser fan from your home a/c unit and see how your unit will react (if you don't have a high pressure switch to catch it). Off subject but believe it or not some residential units still don't have high and low safety switches on them.
APLUS [ View ] [ Email ] [ Blogs ] [ Car Ads ] Austin, Texas
 
Posted by 1carguy  -  06/09/2007 12:52 AM
Here's an update boys: First, thanks for everyones input. Almost every conclusion that was made certainly could have caused the symptoms I was having. In fact with all this information, I started testing the system further. Bottom line was excessive head pressure. With no air flow over the condenser, the head pressure went off the scale. I wired in a relay to kick the fan on when the compressor engaged and problem went away. Ran it for 15-20 minutes and air temp out of the duct was under 40 degrees. I was going to leave it this way but today I got a call from Mark at Vintage Air...seems he read this thread and decided to call and see if he could help. Man, was I impressed! Not only with his interest in supporting their products but in the power of this website!!! After talking about the problem, he convinced me to install a trinary switch rather than just having the fan run all the time with the AC on. I'm surprised that this switch is optional and not part of their kit. Anyway, I ordered a switch that can be installed with a fitting at the expansion valve under the dash rather than at the drier under the hood. Hopefully the problem is nearly solved!
1carguy [ View ] [ Email ] [ Blogs ] [ Car Ads ] Pleasanton, California
 
Posted by 1carguy  -  06/17/2007 06:51 PM
Installed the trinary switch today, and it seems like it has solved the problem. After a few minutes of operation, the fan kicked on, and the AC was cold. When idling, the fan turned on and off but running down the road it never came on (today it's about 85 degrees) and the compressor never acted like it was going to seize up. Finally I think it's fixed! Thank you guys for the good advice.
1carguy [ View ] [ Email ] [ Blogs ] [ Car Ads ] Pleasanton, California
 
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