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Old 08-09-2010, 07:32 PM
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A/C Condenser Question

I`m not sure if this is the correct forum for it as it`s not really a electrical issue, but I`m trying to find out what temp does the A/C condenser get to?
I notice on older GM vehicles they count on the clutch fan to kick in when the vehicle comes to a stop to keep the airflow moving. Needless to say down here in the deep south lately it`s been getting to 100 with 70% and higher humidity. When Stopped the air gets luke cool and not what I`d call cold. I want to add a pusher electric fan in front of the condenser to keep it cooler so it`ll keep the air cold at stops. Sometimes the stop lights around here last a while depending on traffic conditions. If I can find out what temp they run I`ll know where to set the electric fans thermostat at so it`ll kick on when I come to a stop. Thanks for any help.

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Old 08-09-2010, 08:10 PM
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Quote:
Originally Posted by DoubleVision
I`m not sure if this is the correct forum for it as it`s not really a electrical issue, but I`m trying to find out what temp does the A/C condenser get to?
I notice on older GM vehicles they count on the clutch fan to kick in when the vehicle comes to a stop to keep the airflow moving. Needless to say down here in the deep south lately it`s been getting to 100 with 70% and higher humidity. When Stopped the air gets luke cool and not what I`d call cold. I want to add a pusher electric fan in front of the condenser to keep it cooler so it`ll keep the air cold at stops. Sometimes the stop lights around here last a while depending on traffic conditions. If I can find out what temp they run I`ll know where to set the electric fans thermostat at so it`ll kick on when I come to a stop. Thanks for any help.
I lived in fla. for about 18 years so i got to do a lot of a c. I really never bothered to check the condenser temps unless i was looking for a blocked one. They get pretty warm to the touch probably 165 175 degrees.More important would be the pressures your system is at during the highest temp of the day. down south when at 95 + degrees can be a challenge for a 134a system but airflow is the key as well as pressure. Your chevy has a CCOT system (Clutch Cycling Orifice Tube).It uses a low pressure switch at the accumulator. On a 95 degree day pressures should be around 40 on the low (35 would be better) and 250 -265 on the high side.If the pressure is to high it can be for several reasons but it is most likley lack of airflow when at at the stop light.If you look at the gap between the condenser and the radiator it should be sealed by something like a rubber like flap or foam strips. You can gain a few degrees by tightening up the area to insure airflow at stoplights.I have used thick weatherstripping for that.Also run with the a c on recirculate as the air inside will cool better as it is allready dehumidified and cooler than outside air. after that if you still cant keep the low side pressure down it could be a weak compressor. check the pressures first ,tighten up the air gap at the condenser and as far as a fan it would be better to find a pressure switch to turn on the fan as most manufacturers do on newer cars if you decide to add one.Trouble with that is most of them are a transducer (sensor) and it feeds a pcm with a value and the pcm decides when to turn on the fan.On another note I had the same thing with my 1990 f 150 and I had it tightened up a well as possible and I was leaning torward an extra fan for the exact same reason. I wrestled with the same question how to turn it on only when needed.I dindt think of it at the time but I could have hooked the relay coil for the fan to the brake light switch.
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Old 08-09-2010, 08:15 PM
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on another note put the fan circuit on two relays one for the brake light switch and one that powers up with ac request. You can tap that at the pressure switch on the accumulator. make the brake light switch relay turn on the fan relay that way it only runs the fan when the ac is on
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Old 08-10-2010, 12:55 AM
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Quote:
Originally Posted by latech
....and as far as a fan it would be better to find a pressure switch to turn on the fan as most manufacturers do on newer cars if you decide to add one.Trouble with that is most of them are a transducer (sensor) and it feeds a pcm with a value and the pcm decides when to turn on the fan...
I agree that it would be better to switch the electric fan using a pressure switch rather than a condenser temp switch. As far as pressure switches go, you could just use a standard trinary switch plumbed into one of the high pressure lines. This one from Vintage Air would turn the fan on whenever the high-side pressure exceeds 254 PSI.

Vintage Air Catalog Page
Link to Summit Page

Quote:
Originally Posted by latech
I dindt think of it at the time but I could have hooked the relay coil for the fan to the brake light switch.
Just a thought... What would happen if you turned on the Hazard lights? Wouldn't the fan turn on and off?

Quote:
Originally Posted by latech
on another note put the fan circuit on two relays one for the brake light switch and one that powers up with ac request. You can tap that at the pressure switch on the accumulator. make the brake light switch relay turn on the fan relay that way it only runs the fan when the ac is on
That sounds workable.


Hope this helps...

Last edited by Joe G; 08-10-2010 at 01:00 AM.
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Old 08-10-2010, 01:36 AM
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"Just a thought... What would happen if you turned on the Hazard lights? Wouldn't the fan turn on and off?" <---I like that, Joe G!!! Made me smile...thanks
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Old 08-10-2010, 05:47 AM
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I put a pair of cheap 12" pushers on an earlier 351W F150 that had been converted to R134a, it ran nice and cool going down the road, but got much warmer sitting in traffic. I just triggered the single fans relay with the hot wire from the low pressure switch, so the fans came on with the AC. HUGE difference in AC cooling, even moving down the road.
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Old 08-10-2010, 03:32 PM
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I dont think that the hazards would cause the cold side of the brake light switch to become hot and turn the fan circuit on and off but I guess it may ,that is a good headscratcher.I think the brake light side would be disconnected in the hazard position.Kinda funny though. My thought was to only have the fans when truly necessary at a stop light and not while moving. I do like the idea of the pressure switch.
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Old 08-10-2010, 04:11 PM
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Quote:
Originally Posted by latech
I dont think that the hazards would cause the cold side of the brake light switch to become hot and turn the fan circuit on and off but I guess it may ,that is a good headscratcher.I think the brake light side would be disconnected in the hazard position.Kinda funny though....
Indeed it is a head-scratcher, but think about what happens when the hazards are on and you step on the brake.....The hazards stop flashing and the brake lights glow steady. To my way of thinking, that indicates that there is no disconnect between the brake cold and the flashing turn/stop lamps while the hazard lights are activated. If they were not connected, stepping on the brake with the hazard lights on would have no affect on the brake lamps - they would just keep flashing.

I like your second idea as an easy alternative to installing a pressure switch, unless a port already exists to screw a trinary switch into.

Joe G.
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Old 08-10-2010, 06:31 PM
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I was thinking about the backfeeding situation with the brake lights and a lot of cars are that way ,then i thought some cars are exceptions. Mid 80 s gm s that have the yellow turn signal lenses in the back like some mid 80 s camaros delta 88 etc.I think it is a valid point.A diode spliced into the brake cold side feed to the turn switch would Rectify ( Ha Ha ) the situation though.
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Old 08-10-2010, 08:47 PM
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I have no idea, but would a smaller pulley on the compressor help spin it faster? Might help at idle.
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Old 08-10-2010, 08:53 PM
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Quote:
Originally Posted by Argess
I have no idea, but would a smaller pulley on the compressor help spin it faster? Might help at idle.
That would raise the system pressure on the high side. As the pressures are allready high it needs to shed the heat it is pumping to cool. More air flow will shed the heat and bring the pressures down some. The compressor will live longer too.
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Old 08-10-2010, 08:58 PM
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I'm sure you're right. I just thought that instead of increasing the air-flow,, you might accomplish the same thing by increasing the refridgerant flow....as long as a change in pulley didn't affect higher rpm operation. Oh well.....I better shut up as it's obvious I don't know. But I did try to help....
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Old 08-10-2010, 09:05 PM
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Hey dont feel bad. You dont know if you dont ask. I dont know it all but the theme is the same for both of us were willing to help someone who needs help. You may have asked the same question someone else was going to ask . So it helped anyway. There are lots of guys here who know a lot about racing , I work on everyday drivers and I havent had much of a chance to explore racing and hottrodding. I have worked on all makes and models for a long time though. But that wont help my E T.
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Old 08-11-2010, 06:01 AM
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If you want a leg up that will help cooling, check out the Smart orifice tube, or VOV. They can really make a difference. I use them exclusively now. I maintain a fleet of taxis, and they not only help the system cool better, they seem to make compressors live longer as well,
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Old 08-12-2010, 09:27 AM
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If the car has a hot water valve in the system,just make sure that hot water isn't going throughwhen its supposed to be closed in a/c postion.that will give you the same result,at low or high rpm.
Paisano
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