AC only cools on decel

[DodgeMech]

so, man, i've had an adventure with the ac on this thing

when i first got the car, i sucked down the freon, and measured it, it had a bit over a pound, which according to all info i found, was in line, so i knew it had no leak, just didn't work

after doing some searching, i came to the conclusion of buying a RCV for the compressor...i get under and look at it, order the one with the circlip...when i get around to actually installing it, turns out my damned car has the hex bolt one...so, i order it...then install...

i bought the car in october, i get around to finally installing the correct rcv in about january, maybe march...damned thing still didn't work

so i resign myself to the fact that it's either electrical, or a failure in the compressor

this past week, i was driving to school one morning, and i felt cold air out the vent...turned ac on, and by god, it worked, at speed, not at idle, which is fine, car has some crap looking aftermarket fans on it, anyway, all week, it was intermittently working, but over 50 percent of the time

get in it yesterday, and it doesn't work at all...except when not on the throttle

as in, i can be in 5th gear, let off the gas pedal, and let the engine coast down, and the air gets cold...but, if i set cruise, within seconds, it gets back warm

i'm gonna say this is prolly some type of weird mechanical failure inside the compressor, and i found a kit on the ebay that comes with the compressor, oil, a condensor, and a h valve for about 50 bucks cheaper than i can find a compressor only local

tl;dr

anyone ever have the ac on their jetta only work when not on the throttle? and if so, did a compressor fix it?

i'm assuming here that all the electrical side of things is fine...

 

[firehawk618]

Since it sounds like you have the means of checking an a/c system why don't you put some gauges on it and see if the compressor is working or not instead of guessing?

 

[DodgeMech]

i can't exactly test the only on decel thing with a set of gauges...can't close the hood and such and drive down the road with a manifold attached

it's obvious it works, but like i said, only when on decel, not at steady rpm, or accelerating

i know everything else works, down to the fans coming on and all, just it only cools when i'm off the throttle in gear...if i set cruise at an rpm while it was working, it quits within 30 seconds or so

i'm just hoping someone has had their car do this before

to me, i would think it's a compressor issue...but it's hard to check pressures while driving

 

[firehawk618]

i can't exactly test the only on decel thing with a set of gauges...can't close the hood and such and drive down the road with a manifold attached

it's obvious it works, but like i said, only when on decel, not at steady rpm, or accelerating

i know everything else works, down to the fans coming on and all, just it only cools when i'm off the throttle in gear...if i set cruise at an rpm while it was working, it quits within 30 seconds or so

i'm just hoping someone has had their car do this before

to me, i would think it's a compressor issue...but it's hard to check pressures while driving

ok, if it only works on decel then that tells me it doesn't work when idling in a shop bay with your gauges hooked up. Pretty easy starting point if you ask me since you have the tools.

 

[relumalutan]

Your radiator fans are not working. That's why the AC only works while driving and not at idle.

 

[dandywriter]

Fan control module is part of the fan assembly. See thread http://forums.tdiclub.com/showthread.php?t=358553&highlight=a/c+fan+sensor

My a/c was weak until I replaced the module, which requires a fan replacement. Now blowing cold...

With the Texas heat, it must be slightly uncomfortable without a/c.

 

[icecap]

Radiator Fans

Fan control module is part of the fan assembly. See thread http://forums.tdiclub.com/showthread.php?t=358553&highlight=a%2Fc+fan+sensor

My a/c was weak until I replaced the module, which requires a fan replacement. Now blowing cold...

With the Texas heat, it must be slightly uncomfortable without a/c.

Hi guys. I haven't been on this site for ages but decided to drop in and look around again. I just went through this identical issue with my A5 Jetta. The A/C worked fine driving down the road but would blow warm air if stopped in traffic. I scanned for codes with VCDS and found a code for A/C high side over pressure and also found that the fans didn't run as soon as the A/C was turned on although it never indicated engine overheating.

I should have suspected something was wrong since before the A/C problem I became aware of excess fan noise that sounded like a jet engine running under the hood and was most noticeable immediately after stopping the engine. It turned out that the smaller passenger side fan had a seized brush and the larger driver side fan ran at maximum speed until it burned itself out.

I was able to repair the smaller fan motor and replaced the larger one that has the variable speed controller in it. As soon as I started the car and turned on the A/C both fans started and my A/C has worked perfectly ever since.

 

[firehawk618]

^ I also fixed my smaller fan just last weekend. The infamous stuck brush was in fact the problem with mine also however I doubt this is the OPs issue. Works only when decelerating tells me the fans play no part in this.