Tricky AC problem
07-10-2011, 02:56 PM
#16
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"Actually while driving and turning lites on (while AC running) you can hear recirculation flap shift."
That would indicate to me that the problem is an interruption in power (or ground)to the HVAC head unit, not the clutch power.
That would indicate to me that the problem is an interruption in power (or ground)to the HVAC head unit, not the clutch power.
07-10-2011, 03:13 PM
#17
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With light switch off potential in clutch wire is 11.0v. With light switch on the potential in the wire is 0.0v. Not just a draw down to below the threshold the clutch activation. Actually while driving and turning lites on (while AC running) you can hear recirculation flap shift. While driving having the AC on barely causes voltimeter needle to drop - clicking the blower fan speed up does so more relative to pushing the AC button on.
07-10-2011, 05:15 PM
#18
Nordschleife Master
Thread Starter
I still feel it was on the install of the alarm as I stated earlier the parking lights get tied in. Does the 928 have positive or negative switched parking lights ? This will let me know how the pulsed parking light relay of the alarm is connected to the 928. - When you refer to the HVAC head unit are you specifically referring to the AC relay or the entire board ? - Wally please pardon the simplicity of this question - How does one interrupt the ground (?) when turning a switch on/off as in this case ?
Wally, your knowledge has helped me often through Nichols site and email keepers. I can't tell you how I appreciate your singular expertise, but also your willingness to share it.
Kindly,
Craig Schiff
07-10-2011, 11:36 PM
#19
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Craig,
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
07-11-2011, 12:44 AM
#20
Nordschleife Master
Thread Starter
Wally,
Thank you for the concise reply. It gives me a much better feel for the 'tall grass' I am walking in (an outside invasion to 928 electrics). I do want to neutralize the AC issue, but still leave the Code Alarm functional. That is why I took the time to locate installation manuals online and they are relatively simple (even for me !). Up here in Presque Isle it's either me or... me.
I will let you know of my success. (One has to keep the faith)
Thanks Again,
Craig
Thank you for the concise reply. It gives me a much better feel for the 'tall grass' I am walking in (an outside invasion to 928 electrics). I do want to neutralize the AC issue, but still leave the Code Alarm functional. That is why I took the time to locate installation manuals online and they are relatively simple (even for me !). Up here in Presque Isle it's either me or... me.
I will let you know of my success. (One has to keep the faith)
Thanks Again,
Craig
07-11-2011, 02:32 PM
#21
Nordschleife Master
Thread Starter
Craig,
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
Also to note - the headlight switch bulb illumination is dimmer than the other pod switches. As best as I can see, I find no splicing into the ground from the controller. I have found the feed from the alarm controller to the headlight switch, and am considering disconnecting it. I will lose the the flashing when the alarm is activated/deactivated via the remote, but that is OK. I never pay attention to that anyway. I use the audible chirps as I walk away from the vehicle. I think this will free the light switch from the HVAC issue, but I am still curious as to the origin of the issue. Any thoughts ?
Craig
07-11-2011, 02:58 PM
#22
Nordschleife Master
Thread Starter
Wally,
Disconnected the light switch feed to the alarm controller.
AC with lights off and ON.
Alarm functions as it should and as it had.
Still curious about the original hiccup.
Craig
Disconnected the light switch feed to the alarm controller.
AC with lights off and ON.
Alarm functions as it should and as it had.
Still curious about the original hiccup.
Craig
07-11-2011, 03:30 PM
#23
Nordschleife Master
Thread Starter
Craig,
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
It is entirely possible that the problem is linked to the alarm system. My response was just to try to help locate the cross-connection.
If the problem was just that the compressor cut out when the lights are turned on, the cross-connection could be either in the power circuit from the HVAC head (the box in the dash that contains the controls and the control circuitry for the HVAC system) to the compressor, or in the power or ground circuits for the HVAC head itself.
Since the problem includes the recirculation flap changing when the lights are turned on, the problem is very, very unlikely to be in the compressor power circuit, but must be in one of the circuits operating the HVAC head.
The lighting circuits on the 928 are all power-controlled circuits, meaning that the switch powers the circuits going to the lights, and the circuit from the lights to ground are unswitched. This means that the alarm system must apply power to the parking light circuits to make them come on.
The HVAC head unit is grounded by one brown wire that runs from the head unit to a welded connection where several brown wires come together, and from there to a "Masse Point" or ground point, which is usually a bolt or stud on the body metal. I do not remember whether that one grounds to the point located above the Central Electric Panel under the passenger floor, or to the point located on the steering column support.
I am speculating that it might be possible that the alarm installer connected one of his system's wires to the HVAC head ground wire. If so, applying power to that wire can override the HVAC ground, killing all HVAC control.
I would start by finding the brown ground wire coming out of the HVAC head unit and following it until it attaches to a ground point.
Let us know what you find.
The only ground feedback point (I think) is at MP IV. Both the light switches and the HVAC controller share this Masse Punkt.
Craig
07-11-2011, 05:44 PM
#24
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Hmmm...
It might be interesting to carefully clean MP IV. If there is high resistance at the ground point, it might be enough to kill the HVAC - but that doesn't explain why it works now.
It might be interesting to carefully clean MP IV. If there is high resistance at the ground point, it might be enough to kill the HVAC - but that doesn't explain why it works now.
07-11-2011, 05:57 PM
#25
Nordschleife Master
Thread Starter
Wally,
As I mentioned earlier the alarm controller pulsed relay wire will attach to either the light output ground or the 12v in depending on whether the vehicle's lights are switched or un-switched. I think the installer just got that wrong. Thanks a million.
Craig
As I mentioned earlier the alarm controller pulsed relay wire will attach to either the light output ground or the 12v in depending on whether the vehicle's lights are switched or un-switched. I think the installer just got that wrong. Thanks a million.
Craig
07-11-2011, 10:32 PM
#26
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Follow the lead for the lamp in the Climate Control unit. You will see that it ties into the fog lamp switch. The lamp lead ties into the control relay in the Climate Control Head. My guess is that alarm system was shunting the relay in the Control Head thus killing power to the ac clutch.
07-19-2011, 11:12 AM
#27
Electron Wrangler
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Interaction betrween unrelated functions is almost always a grounding issue. Disconnected grounds or poor connections needing cleaning.
For an alarm - you'd probably be best flashing the turn signals (for confirmations) and will need 2 relays or a relay and 2 diodes for this. Ext. lighting is switched in the positive line with a direct ground to the bulb. Note that even marker lights are side specific on 928 and this is unusual. It is typically no more effort on a 928 to flash the turn signals that are brighter and better placed for all round visibility.
Alan
For an alarm - you'd probably be best flashing the turn signals (for confirmations) and will need 2 relays or a relay and 2 diodes for this. Ext. lighting is switched in the positive line with a direct ground to the bulb. Note that even marker lights are side specific on 928 and this is unusual. It is typically no more effort on a 928 to flash the turn signals that are brighter and better placed for all round visibility.
Alan
08-06-2011, 03:24 AM
#28
Nordschleife Master
Thread Starter
Interaction betrween unrelated functions is almost always a grounding issue. Disconnected grounds or poor connections needing cleaning.
For an alarm - you'd probably be best flashing the turn signals (for confirmations) and will need 2 relays or a relay and 2 diodes for this. Ext. lighting is switched in the positive line with a direct ground to the bulb. Note that even marker lights are side specific on 928 and this is unusual. It is typically no more effort on a 928 to flash the turn signals that are brighter and better placed for all round visibility.
Alan
For an alarm - you'd probably be best flashing the turn signals (for confirmations) and will need 2 relays or a relay and 2 diodes for this. Ext. lighting is switched in the positive line with a direct ground to the bulb. Note that even marker lights are side specific on 928 and this is unusual. It is typically no more effort on a 928 to flash the turn signals that are brighter and better placed for all round visibility.
Alan
Greetings. Thanks for the reply. Pardon my tardiness, as I just returned back home after 3 weeks. On the way back, cruise control on climbing a mild grade I perceived a 'pop', and cruise control gone for the rest (200 miles) of the trip. On initial diagnostic I find the cable severed at its attachment point up top hiding under the sleeve. Back to AC- light switch issue. Will delve into more. After disconnecting feed to 31 at the light switch from the alarm controller, I had resolution for a day or two. I'm still having trouble finding the common between the lite switch and the AC relay. Will keep you posted. Thanks again for your attention. Craig
08-06-2011, 09:54 AM
#29
Team Owner
BTW does your car have a factory alarm?
I have seen this a few times where an extra alarm was installed over the factory alarm,
it only creates issues with other systems, restoring the car to no alarm status results in proper function and usually less battery drain.
get a used CC cable and install it.
I have seen this a few times where an extra alarm was installed over the factory alarm,
it only creates issues with other systems, restoring the car to no alarm status results in proper function and usually less battery drain.
get a used CC cable and install it.
08-07-2011, 06:54 PM
#30
Nordschleife Master
Thread Starter
BTW does your car have a factory alarm?
I have seen this a few times where an extra alarm was installed over the factory alarm,
it only creates issues with other systems, restoring the car to no alarm status results in proper function and usually less battery drain.
get a used CC cable and install it.
I have seen this a few times where an extra alarm was installed over the factory alarm,
it only creates issues with other systems, restoring the car to no alarm status results in proper function and usually less battery drain.
get a used CC cable and install it.
Thanks for the post. According to the option codes for the car, she should have an alarm. When I remove this 'outside invader' I will check the original alarm control behind the glove box. A question - Is it safe to just remove the 'outside' alarm control unit or do all the splicings etc. have to be mended as well ? Listen to this - I found the WD for the alarm unit installed. I noted a ground for the disarm switch had become disconnected from its chasis connection. I reconnected and the AC worked fine with the light switch off, but when turned on IT KILLED THE RUNNING ENGINE AND THE SIREN WENT OFF ! I want this thing out of the car, but am concerned about the removal operation. BTW Bowden cable on the way.