B5.5 Passat A/C,un-able to fix!!!!!

Kavs

Right hope somebody might be able to shed some light on this problem, its driving me insane!!:mad:
Got a 02 passat sport tdi with climatronic a/c,
but as you've guessed the ac does'nt work.

-So first thing i did was get it gassed up ,the system was fine no leaks etc. and re-gassed fine, still no cold air!

-Then brought it to mechanic and read the fault codes, came up with fault on the pressure switch, so duely replaced the pressure sw, that cleared the fault
,still no cold air!!

-The mechanic had a spare climatronic unit for the cabin so we swapped it out to see if that was the problem ,
still no cold air.

-getting annoyed at this stage, it appears that the compressor is not firing up,so mechanic tells me that it has to be replaced!! = €500!

-done a bit of reading up on the problem and it appears that 04 - 05 models had a problem with faulty relays(bad solder joints), so I said i'd have a look
turns out I have the older type mechanical relays.So just out of curiosty i popped the cap on the main a/c relay and held it closed ,turned the climatronic on and sure as hell the compressor fired up and lovely cold air was working really well!!(mind up the aux fan was running at full speed!)
so it appears the compressor is perfect...

-So back to mechanic yesterday ,we change out the relay for a spare he had but still nothing.the relay will just not engage by itself,
does anybody know why this is?? my mechanic is stumped.

we checked voltage at the relay socket and there is voltage at 3 of the pins constantly (climatronic on/off).

sorry about long post thanks for reading.
any help would be greatly appreciated!

DublinDilbert

Based on what i'm reading, if you push together the contacts in the relay the A/C compressor kicks in....

Assuming the relay is ok (very east to test on the bench), basically the coil of the relay is not getting power from the module that controls the A/C. You should try measure the coil voltage @ the relay. Also see if you can measure the voltage coming out of the A/C control unit...

Mr.Diagnostic

To repair a problem like that the man working on it needs 3 things.
An in depth understanding of how the system work.
Tech data for the system (wiring diags).
A quality scan tool for fault codes and live data.
If even one of the three is missing the chances of an accurate diagnosis is greatly reduced. You had a close call with a €500 euro compressor which could have been easily checked.

From what you have posted it sounds like the control unit is not switching the relay to bring the compressor in or there is a wiring problem between the controller and the relay. What needs to be checked is the inputs for the control unit (pressure, temp etc) and the outputs (relay control signal etc), followed by the wiring.

Kavs

ya i'll try that ,but we did swap out both the relay and the climatronic unit with spares and that did not fix the problem. I think the system is more complicated than I realise, eg. theres 3 relays in there for controlling the fan speed.(response to dilbert there)

Kavs

I know a good auto-electrician is needed but he would'nt be long racking up €500 in labour costs!!

Kavs

bump

DublinDilbert

Kavs wrote: »

I know a good auto-electrician is needed but he would'nt be long racking up €500 in labour costs!!

Probably unlikely to cost anything near that.... If he's a good auto electrician, he'll want to get cars in one door and out the other door... You'd be surprised how cheap it might be.

As what Mr.D said above, someone with the correct scan tool & knowledge, will be able to test the A/C system very quickly... If the scan tool is any good they'll be able to "force" that output on and check that the relay is kicking in...

Failing that, i'd be checking the voltage going to the coil of the relay. It could be as simple as a loose connection, bad ground or b+ connection on one side of the relay coil.

Kavs

Got talking to an auto- electrician today and as i feared he had no idea of the fault, says it could take a couple of days or a couple of hours ,and at €60/hr , I don't think I'll be in any hurry to bring it to him! he was hinting that it could be an ECU problem which would be hugely expensive to replace!

So I'm gonna spend the weekend pulling fuses and relays and traceing cables to see if i can turn up anything... in the end if all else fails im just gonna install a manual overide switch.