HVAC Failure

[thejack]

Hi gents,
I'm an Italian boxster owner and I'm experiencing a faulty ac climate control since the car has been serviced at a porsche dealer.
So, let's start from the beginning and let me apologize for my English which isn't as good enough.
My 97 986 has been serviced at 153000km, it got new clutch, new RMS, water pump and a check at the IMS bearing plus oil, filters and other small stuff.
When I picked the car up from the dealer I noticed that the ac compressor was not running as it was supposed to do. I tried to turn it on by hitting the button and the only thing that happend was the ice icon on the lcd that lighted up. But when I released the button, the ice icon turned off immediately.
Dealer told me that the head unit must be replaced. But he didn't do any kind of dyagnose to state it. I asked him if any action done aorund the engine could have caused some problem but he assured he didn't cause the problem. To show me he was right he just brought another head unit from a 996 and connected to mine showing the ac running smooth.
It happens, randomly, that when I crank up the engine the head unit seem to work for a while then it stops, without any chance to turn it up again.
Someone experienced something similar?
I have another head unit coming from a 1996 Audi A3 with hella code 5HB 007 608 00. My original one has code 5HB 007 691 00. Anyone knows if they are compatible?
Thanks all for helping.

[extanker]

if the a/c was working before this work it does seem odd,alot of work was done any a little bit around the compressor but they did plug in a "known good unit" and it worked soooo....

[thejack]

Ok, so you think the head unit is probably gone. I wonder if there is some extra check to do to be sure it's the root cause. I say this because dealer connected the new unit just a few seconds to show me the ice icon lighted up on the display but, it usually come up each time I crank up the engine after a short stop. Then it goes off after seconds from start. Anyway, I have another head unit coming from an Audi A4 with a different code but from same year. Could it fit my 986?

[kabel]

It is possible you have a bad ignition switch.
When mine went bad I could wiggle the key and the hvac would sometimes cut out.

[thejack]

Thanks kabel, I thought the same as you did although I had the switch changed just a month ago. In my 986 the steering column switch isn't the updated one so I've been able to change only the electric switch.
To be honest, just yesterday, I had a stereo head unit breakdown. It just gone off without a known reason and come back operative after minutes. This has led me to think abuto the switch, but I tried to move the key turning off and on again with no success.
Will check. But I'd like to know if the audi head unit could fit my 986 without other issues.

[thejack]

Today have noticed another strange thingh about my hvac unit. I put the car out of the garage ant let it at idle just not to turn the engine on and off just a while after. The engine ran for about 20 min and the for all the time the car ran ac was working great. Then I decided to go for a small ride and, surprisingly, the ac got off after few meters driving.

Is this still relating to the head unit malfunction or have I to point in another direction?

[thejack]

Well, yesterday the new head unit arrived. I put the new one on and nothing changed.

The a/c compressor starts and after a while it shuts down wirth no way to make it working again.

The ioce icon lights up as long as I keep the button pushed.

This isn't a head unit related issue.

Some tips??

[extanker]

put gauges on the high/low a/c lines

[thejack]

Done today. Pressure is ok.

Any other check?