GTS electricals

[davidb3]

Hi Chaps can anyone please help; my 1995 GTS Auto, after 12 trouble free years has developed an elec issue that's proving difficult to diagnose. The A/c and heater blower have intermittently failed for some time but have always started again without intervention. They have now failed completely together with the radiator/a/c cooling fans. I have checked all of the obvious, fuses, relays, ground points, blower and fans which work with a direct feed. The problem appears to be on the control side as the relays are not initialising. Can someone please point me in the right direction please.
Kind regards
David

[Mrmerlin]

try jiggling the key back and forth if this makes it work then the ignition switch is failing

there are 2 relays for the HVAC system replace them ,
also replace the fuse ,
and consider replacing the relay in HVAC head unit look at the CE panel and see if water has been getting into the system ,
also replace the window relay.

NOTE if you dont want to replace any of these relays then take them out and test them see if they all will close with 12v and also open them and inspect the contacts internally smell them for burning. also remove the fan connectors at the radiator inspect them for corrosion

[davidb3]

Thanks for that Mrmerlin, I have tested/replaced all the fuses and relays, removed, cleaned and re-sealed the fan and there was no water ingress so I'll try your other suggestions as soon as it stops raining, I live in Manchester!!

[Alan in AZ]

Change the "Supply" relay also (Relay X)

Alan

[davidb3]

Thanks for the suggestions chaps, tried everything and eventually booked the car into Pro-Porsche Brighouse, took Richard a couple of hours to find that 3 alarms/immobilisers have been fitted in the past but not fully removed. One or all were corrupting the control box. Stripped out all of the old wiring and everything's working fine.
Perhaps something to look at if you have a pre-owned car.

[pcar928fan]

Man, I HATE aftermarket alarm systems!!!!! Just one more example of why they should NEVER be installed and if the car has one they need to be FULLY and COMPLETELY REMOVED!!!

MrMerlin, I was with you on this one! I was thinking ignition switch as well! I take that as a victory for me...anytime I am thinking along the same lines as you when it comes to a 928 problem diagnosis I know you are either sick or I am a really lucky guesser! LOL!

[Alan in AZ]

Somehow I still doubt this was the direct cause of this issue... you sure it hasn't recurred...?

This really sounds more like an ignition switch issue or a supply relay issue.

Alan

[Danglerb]

Maybe the old immobilizer interrupted the circuit from the ignition switch or one of the relays?

OTOH corroded connections can be slightly cleaned just by some wiggling around.