Random electrical gremlins
Thread Starter
Racer
Joined: Jan 2007
Posts: 369
Likes: 0
From: Sydney, Australia
Random electrical gremlins
Wondering if anyone can advise. My 1990 C4 has been displaying some weird behaviour. First it was the spoiler not raising (see earlier thread here https://rennlist.com/forums/showthread.php?t=326096). Now it's tha passenger side window!
Last night, I couldn't lower the passenger window. Tried both the door switch and the drivers side control of the passenger switch. Nothing. This lasted about 20 minutes, then suddenly it started working again. Very odd.
Are these just coincidental events? Or is there something more ominous looming? Are the electrics inter-connected in any way?
Last night, I couldn't lower the passenger window. Tried both the door switch and the drivers side control of the passenger switch. Nothing. This lasted about 20 minutes, then suddenly it started working again. Very odd.
Are these just coincidental events? Or is there something more ominous looming? Are the electrics inter-connected in any way?
Burgled
Rennlist Member
Rennlist Member
Joined: Aug 2003
Posts: 22,383
Likes: 16
From: Altamonte Springs, Fl/Gwynns Island, Va.
If one of the 2 switches for the passenger window doesnt work it wont work at all. Maybe one of your switches is on the way out. Try switching the driver switch with the other 2 next time it happens and see if that works. Those switches are prone to go bad at least for some people.
Burning Brakes
Joined: Feb 2003
Posts: 985
Likes: 1
John
I had a defective passenger switch on the driver side which would sometimes physically stick in the down position after the passenger side window was completly lowered. When I attempted to raise the window after the switch was stuck in this down position for an extended period of time neither the paseenger side switch nor the driver side switch would raise the passenger side window. After a period of time and after the stuck switch was physically moved to the center neutral position (i.e. no power being applied to the window motor) the window was able to be raised by either switch. My interpretation of this effect was that while the switch was stuck in the down position, it continued to supply power to the window motor and in turn caused the wire in the motor windings (or a relay if there is one in the circuit - I'm not sure) to heat up. A characteristic of copper wire (i.e. whether it is a winding in the motor or a relay) when it heats up is that the resistance increases. If resistance increases to the point in which not enough current will flow the magnetic properties of the motor or relay windings will decrease, hence the motor will cease to work. When power was removed, this allowed the copper wire to cool down and regain its' normal resistance at room temperature and in turn the magnetic properties of the motor windings and hence the motor or relay would work again. In my case the switch was physically suspect but in your case it may not be as obvious. I suspect you have a defective switch and the nice thing about these switches is they can be taken apart and their internal contacts can be inspected and cleaned up with a little patience.
Sorry for the long winded explanation
hope this helps
Bill
90C2
I had a defective passenger switch on the driver side which would sometimes physically stick in the down position after the passenger side window was completly lowered. When I attempted to raise the window after the switch was stuck in this down position for an extended period of time neither the paseenger side switch nor the driver side switch would raise the passenger side window. After a period of time and after the stuck switch was physically moved to the center neutral position (i.e. no power being applied to the window motor) the window was able to be raised by either switch. My interpretation of this effect was that while the switch was stuck in the down position, it continued to supply power to the window motor and in turn caused the wire in the motor windings (or a relay if there is one in the circuit - I'm not sure) to heat up. A characteristic of copper wire (i.e. whether it is a winding in the motor or a relay) when it heats up is that the resistance increases. If resistance increases to the point in which not enough current will flow the magnetic properties of the motor or relay windings will decrease, hence the motor will cease to work. When power was removed, this allowed the copper wire to cool down and regain its' normal resistance at room temperature and in turn the magnetic properties of the motor windings and hence the motor or relay would work again. In my case the switch was physically suspect but in your case it may not be as obvious. I suspect you have a defective switch and the nice thing about these switches is they can be taken apart and their internal contacts can be inspected and cleaned up with a little patience.
Sorry for the long winded explanation
hope this helps
Bill
90C2
Rennlist Member
Joined: May 2004
Posts: 656
Likes: 1
From: Fairfax Station, Va. USA
Remove switches. Disassemble. Clean the contact surfaces. Reassemble. It's easy; just be careful. The switches are very simple devices. Problems with them seem to be common. Or you can just buy a new Porsche switch = $$$$.
Also, i've found that a lot of electrical problems, especially in older cars, are traceable to corrosion on the grounds (earths). Try finding, disassembling and cleaning all that you can locate. I hope this helps.
Also, i've found that a lot of electrical problems, especially in older cars, are traceable to corrosion on the grounds (earths). Try finding, disassembling and cleaning all that you can locate. I hope this helps.
Thread Starter
Racer
Joined: Jan 2007
Posts: 369
Likes: 0
From: Sydney, Australia
Thanks for the feedback and info guys. After your helpful advice, I'm convinced it's the door switch and nothing more serious (big relief). Happened again last night, but fiddled with the switch (ie. pushed down REALLY hard) and came good again. I will pull apart and clean as advised.
Cheers
Cheers
