A few A/C questions

[Night Fury]

Do the compressors cycle at all in 1st gens?

 

Does it in any way use less power with the fan speed on low rather than high?(less air flow-->less refrigerant temp increase-->less load on compressor?)

 

It just seems obscenely intense in the 88. Like I can't even leave it on low without suffering hypothermia. Not that I'm complaining, it just seems... unusual?

 

Lets hear all about A/C works in these cars shall we?

[Silentkillzr]

I know nothing of ac, i was thinking of recharging mine but im not sure if the compressor system works at all?

[pshojo]

If your car still has R-12 freon in it, versus the R134, you can really crank out the cold. I had a 89 that had the r-12 and could actually get snowflakes/ crystals to come through the vent. I miss that stuff

[94 olds vert]

My compressor cycles in my GP. I can watch it turn on/off. My AC gets pretty cold right around 37-39F. The other day when I jumped in the car I cracked the windows cause it was hot inside, put the AC on max. Let it go for 10 minutes or so on MAX, then just hit the AC button and lowered it to the second 2 air flow setting by that point in time I was cool and the car stays cool.

 

I know if I put it on the floor and I have flip flops on my toes will start to hurt.

[WhatTheFehl]

I don't recall the A/C cycling in my '95 at all. Only time it would turn off is under heavy throttle.

[Galaxie500XL]

The '95 uses a variable displacement compressor, the idea being it shouldn't have to cycle off and on.

[Night Fury]

If your car still has R-12 freon in it, versus the R134, you can really crank out the cold. I had a 89 that had the r-12 and could actually get snowflakes/ crystals to come through the vent. I miss that stuff

 

R134

[Silentkillzr]

How can I tell if the compressor cycles still is it clearly visible?

 

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[Night Fury]

Yes, but it won't engage if there's no charge in the system

 

It's the bottom, most forward pulley

[94 olds vert]

When the cetnter part of the compressor stops spinning you will notice it. Buck is right with no pressure the AC compressor won't even turn on. There is a way to jump the relay to test if the AC compressor still works.

[Silentkillzr]

Oh okay. I've been wondering because if I try it. I don't feel a bog or notice a rpm drop. I'll have to try and fill it I suppose.

 

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[94 olds vert]

Do your self a favor and find the AC relay. Then jump two connectors with a paper clip. With the engine running you will be able to see the compressor run.

[RobertISaar]

yeah, V5 does not cycle unless you have a charge issue(or as mentioned, in the case of throttle, and in some cars, if the power steering pressure switch indicates high power steering pressure). the compressor will get shut down if high-side pressure gets too high while it running, but it takes something close to 400PSI to cause that IIRC. the compressor also gets disabled if high-side pressure drops below 40ish PSI.

 

 

 

the V5 being variable displacement, the number of pistons in use is entirely determined by how much the compressor has to cool down the evaporator. so a lower fan speed SHOULD have less pistons active since the evaporator won't lose it's temperature as quickly.

 

 

 

 

also, more neat info: having the A/C set to MAX recirulates the air inside the car(which is why you can hear a different noise kick in when you set it as such), regular A/C settings pulls air from the outside of the car. if you want a car to cool down as quickly as possible and it's noticably hotter in the car than outside, keep it in A/C mode for a little while, until the interior is noticably cooler than outside, then switch to MAX.

[Night Fury]

yeah, V5 does not cycle unless you have a charge issue(or as mentioned, in the case of throttle, and in some cars, if the power steering pressure switch indicates high power steering pressure). the compressor will get shut down if high-side pressure gets too high while it running, but it takes something close to 400PSI to cause that IIRC. the compressor also gets disabled if high-side pressure drops below 40ish PSI.

 

 

 

the V5 being variable displacement, the number of pistons in use is entirely determined by how much the compressor has to cool down the evaporator. so a lower fan speed SHOULD have less pistons active since the evaporator won't lose it's temperature as quickly.

 

 

 

 

also, more neat info: having the A/C set to MAX recirulates the air inside the car(which is why you can hear a different noise kick in when you set it as such), regular A/C settings pulls air from the outside of the car. if you want a car to cool down as quickly as possible and it's noticably hotter in the car than outside, keep it in A/C mode for a little while, until the interior is noticably cooler than outside, then switch to MAX.

 

Thanks!!

 

And I did know the max/ ac thing, and do as such.

 

I normally run max, unless like you said, it's cooler outside the car than inside

 

Thanks again for the info. It's variable. Basically what I wanted to know. <3 Saar

[MonzaRacer]

First of all r12 or r134a make zero difference in the temperature output of the system. R134a will make same temps as r12 IF system is operating properly. Cycling is based on PRESSURES.

Now proper refrigerant flow is based on either the orifice tube OR expansion block. Those control flow and how cool the evaporator gets. Most of the newer cars run tighter orifice openings, this is also why many techs that do conversions use blue Ford orifice tubes because they are smaller.

Now for most peoples use basically swapping in a r134a orifice tube from a newer model of w body should allow the older car to be converted successfully and allow it to work more efficiently.

Generally the only issue in conversions is insufficient condenser area. Sometimes fixed with more air flow, fan on time or an auxiliary condenser added to the car.

Also dont forget running most of these cars at max ac operates it in recirculate mode,,anything else had to cool and dehumidify all the air coming in AND you.

Also on variable displacement compressors on older r12 cars there used to be an updated control part that modifies the variable operation for R134a.

Now another trick is that SOME converted cars STILL need the same amount of R134a as R12.

Basically the trick for conversion is using the proper orifice or expansion block, proper flushing of the old lines, condenser and evaporator and replacement of the drier/accumulator with one using XH5 or XH7(preferably XH7 as it reacts better to residual traces of mineral oil/r12) and swapping to either Cliplite ROC oil or Ester 100.

Everytime I use PAG 150(stock GM PAG oil)in conversions I tend to destroy compressors(I am an ASE Certified Master Tech) the ONLY way of not having a failure was using a NAPA or Delphi NEW replacement. I prefer the ROC oil and you can get it on Amazon pretty reasonable.

Following general rules putting specific amounts in the different parts ,including the compressor. Failure to spread the oil amounts out can destroy many systems.

 

NOW if you use the proper Automatic Adjusting Orifice Tube over a Fixed Orifice Tube you get less load on the compressor and colder evaporator temps.

Some times cycling switches need adjusted or newer versions adapted to older cars.

On conversions I use the pressure method, car running, max ac fan on high, windows open. while at idle operating charge for a steady 28-34 psi low side. your looking for around 200/225 psi if the high side pressures get too high it destroys the system.

Either air flow or aux. condenser area may be required or simply updating to a more efficient condenser from newer vehicles migh also work.

Generally most systems can convert with little to no loss of efficiency.

I have a guy right now with 73 Corvette, he is using AC box and controls from a 78, a compressor and condenser from an aftermarket system, set up as Cycling Clutch Orifice Tube system and his wife in middle of summer last year all hot an sweaty sitting in the car in her bikini found out that the AC work VERY WELL!

Edited July 20, 2013 by MonzaRacer

[Silentkillzr]

I just tried to fill mine. I've got a bad seal right on the compressor. Also did my girlfriends 95 Prix and that seemed to hold and work. I'll try to replace my seal and go again.

 

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[will_s95]

So jealous of you guys... Bought my car missing a compressor, my shop is throwing around numbers like $1500 to fix it all...

[Night Fury]

Don't loose hope... My a/c was literally non existent a couple of months ago. Compressor was seized and bypassed, lines were open, condenser had gaping hole in it.

 

I went to the JY and happened upon a 89 Cutlass Supreme with a converted system, that still had a full charge. I got the compressor, condenser, some lines, and some other misc stuff for about $100. I installed the stuff myself, then took it to a shop for them to finish it up and charge it. They charged ~$400

 

Soooo.... for ~$500 I have A/C that I cannot leave on the lowest fan setting with the vents pointing away because even that is too cold.

 

My only regret is that I didn't do it wayyyyyyyyyyyyyyy sooner!!!