Question for Tom Tuling
Thread Starter
New Member
Joined: Apr 2007
Posts: 13
Likes: 0
Question for Tom Tuling
Hi Tom
I have changed the climatepanel from 1997 to 2000 facelift model, and followed your diagram
that you made for Paul Waterloo, the thing i dont understand is why the A/C high pressure switch F118, needs to be grounded ( pin 2 br/gr ) since it is allready grounded to the A/C ground wire harness ? is there a difference between the 2 groundings ?
Peter
I have changed the climatepanel from 1997 to 2000 facelift model, and followed your diagram
that you made for Paul Waterloo, the thing i dont understand is why the A/C high pressure switch F118, needs to be grounded ( pin 2 br/gr ) since it is allready grounded to the A/C ground wire harness ? is there a difference between the 2 groundings ?
Peter
Banned
Joined: Oct 2000
Posts: 950
Likes: 1
Using a separate ground to prevent electrical spikes on the AC ground wire?
Hello Peter,
I can't remember what I drew for Paul, but I suspect the high pressure switch pins 1 and 2 supply a ground for the compressor relay coil. If so, the reason for a separate ground on pin 2 of the switch would be to prevent a voltage spike when shutting off the relay from reaching the A/C ground wire and damaging electronics in the climate panel.
After turning off current to a relay coil, the collapsing magnetic field makes a momentary voltage spike, sometimes large enough to jump between the opening contacts of a switch. The A/C ground wire in the harness appears to be grounded by the climate panel and used only for sensing, so possibly cannot accept voltage spikes without damaging the climate panel.
The ECON button will not work because the new climate panel is missing some CAN-BUS signals from the instrument cluster to tell the engine rpm, outside temperature, or something like that, so will never turn on the compressor. I forget the details.
Tom
I can't remember what I drew for Paul, but I suspect the high pressure switch pins 1 and 2 supply a ground for the compressor relay coil. If so, the reason for a separate ground on pin 2 of the switch would be to prevent a voltage spike when shutting off the relay from reaching the A/C ground wire and damaging electronics in the climate panel.
After turning off current to a relay coil, the collapsing magnetic field makes a momentary voltage spike, sometimes large enough to jump between the opening contacts of a switch. The A/C ground wire in the harness appears to be grounded by the climate panel and used only for sensing, so possibly cannot accept voltage spikes without damaging the climate panel.
The ECON button will not work because the new climate panel is missing some CAN-BUS signals from the instrument cluster to tell the engine rpm, outside temperature, or something like that, so will never turn on the compressor. I forget the details.
Tom
Thread
Thread Starter
Forum
Replies
Last Post
audithepeanut
Audi 4000 / Coupe GT Discussion
17
Aug 15, 2008 06:10 PM
Wilkie
S4 / RS4 (B5 Platform) Discussion
1
May 30, 2002 03:50 AM
hoTTub
TT (Mk1) Discussion
4
Feb 2, 2001 09:43 AM
