A/C blows cold....but only when cooling fans engage? '02 NB 1.8T

[jaredjulian]

Hey guys and gals,
I'm brand new to the forum and NB world as well. I am puzzled by an A/C issue I have on my new to me '02 NB 1.8T. It's getting cold here so it's not so much an issue now but I wanna start diagnosing it now for next spring/summer. I was told by the previous owner that all it needed was freon for the A/C to work. I took his word for it and a friend of mine did the work for me, he's a NM state DoT mechanic so I trust he knew what he was doing. Sure enough, he finished and it blew ice cold air for that day. The next day it was blowing nothing but hot air. I thought I might have a leak in the system but before my friend checked that out, it started blowing cold again, and then hot again....on and off just like that for about 15 minutes. We then realized when the cooling fans were kicking on, it would blow cold, but as soon as they shut off the air would turn hot. He hasnt had a chance to look into it further but thinks something is hooked up wrong. The previous owner did have the timing belt and water pump replaced shortly before I bought it (receipts to prove it). Is it possible something got "hooked up wrong" when they reassembled everything and that could be causing my problem? I'm no ASE mechanic though I like to tinker here and there, but this has me puzzled. Anyone have any suggestions, ideas?

Gah! Sorry for the novel of a post, I have searched and read many a A/C problem posts but didnt find anything similar to my issue. I'm also sifting through thread after thread of the dreaded "airbag light on" issue, wish me luck!

Thanks for any help, I really like this forum already and plan to be active.

Jared

[D2Beetle]

Check the FCM (Fan Control Module) and the sensor in the radiator, the FCM is connected to it.

[Supercharged98]

First of all, what is the freon pressures? You said it cools as long as the fans are on. So it means the FCM is working. Now, what is causing the A/C system to shut down and cycle on and off? I'm going to say the system is overcharged, and it's hitting the high pressure safety switch and cutting off.
I need the high pressure reading to determine if the expansion valve has a partial blockage causing the shut down, or just overcharged.

[jaredjulian]

I'll have to see about getting the pressure readings, I don't remember off the top of my head from when we charged it.

[jaredjulian]

my friend cant check the pressure for me as he is out of town currently. can i just buy one of those "do it yourself" recharge gauges from autozone and check it that way?

[Supercharged98]

You can buy one, it'll tell you the low pressure only. If you want a complete set, check Harbor Freight. I know they sell them there. Also, check Autozone, they might have a set on their loaner tool program.
If you do get a set, the pressures should be around....
25-35#'s low side
220-230 max on high side

That's for 99 & up NB, 98's are different settings. Don't know why. I think it was a component change in 99.

[jaredjulian]

You can buy one, it'll tell you the low pressure only. If you want a complete set, check Harbor Freight. I know they sell them there. Also, check Autozone, they might have a set on their loaner tool program.
If you do get a set, the pressures should be around....
25-35#'s low side
220-230 max on high side

That's for 99 & up NB, 98's are different settings. Don't know why. I think it was a component change in 99.

I was able to rent a set of gauges from AZ, thanks for the tip on that. My first try at connecting everything was terrible as I had leaks spraying freon out of every connection, I'm thinking I lost a lot of pressure in doing so too. I tightened up all the hoses and finally got it hooked up right, started the car, turned the a/c to high. The low is steady at 33, but the high is insanely low, about 25 I'm guessing as its midway between 0 and 50. Im guessing from what you said the high should be, there's no way it will work now. I'm assuming now I have to add freon to get the high up? My confusion now is how I do I get the high pressure up in the 220-230 range while keeping the low in the 25-35 range?

[Supercharged98]

Something isn't right. Do you have the valves closed on the gauge manifold? Is the compressor clutch engaging? I don't know how you're reading the low pressure on the high gauge.

[jaredjulian]

The clutch engages. The low gauge reads 33, high gauge reads ~25.

[Supercharged98]

When you first worked on the A/C, did you happen to vacuum down the system first. It's starting to sound like the freon has air pocket in the system.

[jaredjulian]

No initially we just put a can of freon in it and it worked fine until the following day. A couple days later was the soonest my friend could look at it to test for leaks and prior to doing so is when we realized it was blowing cold again when the fans switched on and hot when they shut off. I would like to figure it out now if possible but if we can't at least its not gonna be hot for a few months.

[Supercharged98]

I hate to say it, but I think you're gonna have to vac down the system to get any air and moisture out. Then put in a can of oil/freon first, and then top off with freon.

[jaredjulian]

That part I'm not sure how to do so ill see about getting it done later when it gets warm. Thanks for the help though