AC Trouble

[bmike]

98 Jetta Tdi, 5-speed. Coming home the other day when it was pretty warm out and the AC would only put out coolish air, its usually ice cold. This was the first time this season I needed it, about 15 minutes into the trip and the AC came on like it used to. Now just getting the mildly cool air all the time. The fans are coming on, I can feel the compressor engauging when I press the button and I just replaced the ambient temperature sensor anyone have a suggestion on my next step? Thanks.

 

[TonyJetta]

Next step: check pressures.
Hi side should be about 200-220 / low side should be 20-30psi.

Sounds like you have a leak, bad compressor or expansion valve.

Tony

 

[bmike]

I added a half a can of freon, but still no ice. The metal block near the firewall that has an insulated black plastic cover is getting very cold but its not making it into the cabin. Any ideas before it goes to an A/C shop?

 

[TonyJetta]

I added a half a can of freon, but still no ice.

Yeah, but what are the pressures? That will tell more of the story.

The metal block near the firewall that has an insulated black plastic cover is getting very cold but its not making it into the cabin.

That's the expansion valve. If it's getting cold, I bet you are still low on freon. Again, you need to check pressures.

Any ideas before it goes to an A/C shop?

Pressures...pressures...pressures!

Tony

 

[mohawk69]

Is condensate draining from under the car?

 

[bmike]

Is condensate draining from under the car?

No. I bought the HF gauge kit today, will try it later to see what I have for pressure.

 

[bikeprof]

MAKE SURE that the fans are operating, if not, the pressures will be too high(heat), and damage the internals of the compressor..., then trouble.

 

[mohawk69]

If the drains are blocked, it may be as simple as clearing them and allowing them to drain. I don't know where the drain is on the Jetta. On my B4 Passat, it's behind a heat shield near the center of the firewall. My old Rabbit used to do the same thing as well. The AC may be working correctly since you indicated the black plastic is getting very cold.

 

[nhdude]

Sorry to hijack this thread but I'm having a similar problem and had the pressures checked at Pepboys... low side pressure around 50 and high side 225. So, doesn't appear to be low on 134a. Minimal cooling, fans running. Low side pressure seems a bit high?

Thanks to all for the tips... going to check the expansion valve or maybe just replace it and get a recharge.

 

[bikeprof]

New Hampshire guy: Seems that there is LOTS of debris in there and clogging the orifice tube from age and wear.

Drain of 134a,
replace orifice tube AND drier(stuff in there),,
re-work compressor or re-place w/new,
re-fill 134a.
This should bring the A/C to great VW operating conditions...

 

[bmike]

MAKE SURE that the fans are operating, if not, the pressures will be too high(heat), and damage the internals of the compressor..., then trouble.

Thanks for all of the info. From the best I could determine the low was 50 the high was ~150. Can someone tell me if there are 2 speeds for the cooling fans? While I was checking the pressure the fans seemed to get louder and the AC started working. We did double and triple check that the fans would come on when we pressed the AC button, but like I said they seem faster, (louder), now.

 

[TonyJetta]

On that era Passat, they are 2 speed. IIRC, the Jetta is too.


Your pressures are low. However, if you are getting high speed fan, the pressure is coming up. It may be an expansion valve issue.

Tony

 

[krousej]

New Hampshire guy: Seems that there is LOTS of debris in there and clogging the orifice tube from age and wear.

Drain of 134a,
replace orifice tube AND drier(stuff in there),,
re-work compressor or re-place w/new,
re-fill 134a.
This should bring the A/C to great VW operating conditions...

So where exactly does this orifice tube live? I've been researching it for a while now. Different sources say it is there, it's not there. I couldn't seem to find it online anywhere if I would need to replace it. So maybe the expansion valve has one built inside? Every other A/C system has it located in the tube going to the evaporator. (small side) Imediately downstream of the expansion valve.

 

[krousej]

I've found an answer that makes sense....that was quick....thanks tdiclub.com. Check this post out in
Thread: Air Conditioning cycling on and off

If you truly have a SWITCH and not a TRANSDUCER, you can jumper it to test it.

A SWITCH actually has two separate switches in it, one for low pressure and one for high pressure, and will have 4 wires going to it. You have to find out which pairs of contacts are for which switches. I cannot help you with that right now. A Bentley manual is a great place to start.

A TRANSDUCER has 3 wires going to it, and it CANNOT BE JUMPERED without causing damage (just a blown fuse if you are lucky...)

The switch or transducer will be mounted in the same place, in the HIGH PRESSURE line, near the HIGH PRESSURE gauge fitting near the firewall.

It still sounds as if you still need to do some homework. This system does not work like the older systems that many people are familiar with. During normal operation the compressor should never cycle off and on. It does not have an orifice tube, it has a thermal expansion valve. Suction pressure is controlled by an active mechanical valve in the compressor which varies the compressor capacity (volume), not by cycling the compressor off and on.

From this I've determined if the system is going to clog somewhere it's going to be at the expansion valve. Right?

 

[TonyJetta]

From this I've determined if the system is going to clog somewhere it's going to be at the expansion valve. Right?

Yup!

Also...Jetta's & Passat's do NOT have an orifice tube. Expansion valve.

Tony

 

[mohawk69]

Have you resolved this? What did you find?

 

[bmike]

Found that the HF manifold gauge set was a POS, maybe that is why it was on sale. The readings were never steady and the low side connector was leaking freon when attached. I went to Azone and picked up a can of freon with a low side gauge attached and added it, it was reading about 20 and it has been blowing cold air since. We'll see how long it lasts......

 

[bmike]

Well not very long. My son advised me that on Thursday there was white mist coming from the vents with the A/C on. Friday it stopped working, oh well.

 

[bmike]

Looking for some additional help, (hey Tony). Was trying to add some dye to check for leaks and watched the low side pressure go from 55, then the compressor would kick in and the pressure would go to 80 then the compressor would snap off and the pressure would go back to 55 to re-start the whole process again and again.

 

[TonyJetta]

Sounds like the freon you were adding was enabling the low pressure cutoff switch. Once the compressor got the freon, then it sucked the line dry, and disabled the low pressure cutoff switch, thinking the freon was low (it was) and tryng to save the compressor.

You need to evacuate the system, refill with dye, then resume your leak search.

By evacuating the system, the vacuum that is present, will draw (suck) in enough freon to satisfy the low pressure switch.

Tony

 

[bmike]

Finally today, of course after the heat broke, I got the car to a garage with a real A/C recharge unit. It was evacuated for 30 minutes and then we added 30 oz. of freon, the pressures were 5 low 50 high. We then added 10 more oz. and the air cooled to ~51 Deg. and the pressures were 22 low and 50 high, didn't want to add any more. It cools, but not well.

 

[BolaB4V]

Hijack alert! (hand raised) ...sorry but Ive got AC limp mode too.
Sinced Ive had my B4 over 3 yrs now, the AC has been OK (not Ice cold) but comfortable. Couple' of weeks ago I turned it on and not so good.
Ive searched info on repairs and charging but have a couple of questions now.
a) is it typical when car is started, fan switch on, AC button pushed, that only the drivers side radiator fan is running? shouldnt they both come on/
Ive read there is a belt between the two fans. maybe thats toast?
b) whats the difference between refridgerants 134 and 134a?
if any should the B4 only have the 134?

 

[TonyJetta]

a) is it typical when car is started, fan switch on, AC button pushed, that only the drivers side radiator fan is running? shouldnt they both come on/ Ive read there is a belt between the two fans. maybe thats toast?

With the AC on, both fans should be on low speed.

The master fan has the electric motor...that's the drivers side fan. The passenger side fan is the slave, driven by a belt.

With the engine off, and key off/out of the ignition, make sure the fans aren't running - reach in and try to spin the passenger fan. It should rotate freely. Do this at your own risk.

If it doesn't rotate freely, the fan blade/bearing assy will have to be replaced. Autohausaz has a good price.

If it does rotate freely, look for a reason why the belt would have been cut or jump off the pulleys.

In my case, the guide rings around the fan blades were breaking up, and dropped a peice of plastic on the belt, that partially sliced the belt and caused it to jump off the pulleys. It also dropped a piece of plastic on the drive fan, that took a chunk of plastic out of the fan, causing an imbalance. In this case, I had to pull the fan shroud (pull the whole front clip off the car) to replace both guide rings, and the drive fan. The guide rings were sourced from 1stvwparts.com (Auburn VW) and the drive fan sourced from AutohausAz.

whats the difference between refridgerants 134 and 134a? if any should the B4 only have the 134?

AFAIK, only R134A is on the market.

HTH

Tony

 

[BolaB4V]

The belt has jumped off and was sitting on the lower part of the
shroud. The belt looks in good condition, I cant tell why its off . I ll have to pull the shroud. Thanks for the reply ,will post later...more work to do!