505 GTI aircon Quirks

W

Wilko

Member
Fellow Frogger
Tadpole
Joined
Dec 3, 2020
Messages
109
Location
Newcastle
I recently purchased a 505 Executive series 1 and had the aircon re gassed.
The aircon people couldn’t get the compressor to engage. I took it home and discovered by accident that if I selected the aircon before starting the engine, the compressor engaged but if the engine was running prior to selecting the aircon , it wouldn’t engage. Has anyone had this issue?
 
Thanks for that suggestion Beano, but when the aircon is selected with the engine off and the ignition is turned on, the clutch and condenser fan engage and continue to function normally on start up.
But now with the engine running, if the aircon is deselected, and then reselected,
the clutch and condenser don’t re engage
so the ignition switch must be ok and the fault lies elsewhere- maybe in the control circuitry somewhere - it’s an odd fault.
 
It's not a complex system. Sometimes with things like this, people just hotwire stuff. I mean, all it takes is to fit a switch and a relay, which then feeds power to the compressor. Have it mounted discreetly under the dash.
In fact there must be a relay that does this already, and that may be the problem.
 
Beano, thanks again for your input, but that relay is operating the compressor and condenser with the engine stopped. There must be an interlock prohibiting the relay from operating with the engine running and while attempting to select Airconditioning. I need to look at the cct diagram in depth and the aircon controller most likely is involved.
 
Definitely a good idea to study the wiring diagram. A couple of thoughts...

That it engages with the engine off says that the pressure valve is happy, so the gas hasn't all leaked away. However, it doesn't tell you how much grip it has. Maybe it *is* engaging, but slipping badly.

If you put power to the idle-up valve the compressor clutch should energise, bypassing the other circuits. Something like:
  1. locate idle-up. Pull its wire off. Ignition and aircon on and check that 12V is at the wire. (sanity check) If it isn't throw away this advice.
  2. with ignition off, use a jumper-wire straight from the battery + to the idle-up wire. You should hear the compressor clutch engage.
  3. start engine with aircon off. Do the same jumper wire test. See if the compressor is turning.
That might help you to narrow the problem down. Mind you, now that I've typed this, the aircon people probably already did the same thing to get your system filled. They wouldn't have been able to fill it if the compressor wasn't turning. Then they noticed that it stopped as soon as they disconnected the jumper.

I think you're right. Wiring diagram and test light time.

Have fun,

Rob.
 
Rob, thanks for your input. When I discovered how to engage the compressor ( selecting aircon prior to start up ), I took the car back to the aircon blokes and they confirmed after topping the system up that the system was cooling satisfactorily and even cycling the compressor on an off with the thermostat setting. But deselecting aircon and then re selecting with the engine running wouldn’t engage the compressor or run the condenser fan, so something is blocking aircon function with the engine running - have to see if the relay is inhibited somehow. The circuit diagram in the Haynes manual ( pre July 85 applicable to my 505 ) is not easy to follow and some items in the key table differ from the diagram. A location layout would be helpful also.
 
Does sound very strange, but no doubt will make sense once you work it out.

Afraid I can't help much more, though I can offer a sharper version of the wiring diagram in Haynes. This zip file (bit over 2MB) was scanned from an A3 page, and I then went through it in an image editor with my best effort at each of the wire and component numbers. Also chose tasteful shades of blue and purple. There's a plain-text component key in that zip file too in case it helps. Did all that years ago. Hope it saves you some eyestrain. Good luck.

Have fun,

Rob.
 
Thanks Rob for your help and suggestions - I do remember a cluster of relays on the left hand side in front of the battery and one of them is probably for the aircon. How do I access the zip file?
Trev
 
It should work by clicking on the words "This zip file" above. One thing I don't like about AussieFrogs is that, rather than highlight links, it almost lowlights them until you hover over them. Perhaps it's even worse if browsing with a smartphone. Here's the plain text link: https://robswan.com.au/sh/505GTIwd.zip

Have fun,

Rob.
 
Thanks Rob- as you say it doesn’t stand out - I was looking for an enclosure.
Cheers Trev
 
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