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Posted by: yeahmag Feb 14 2014, 08:31 PM

I have a very strange problem. My headlights work fine until I start the motor. Specifically, with the ignition all the way on, but the engine off, the headlights work as expected. With the engine running they will not come on at all. If the headlights are on and I start the motor they turn off, but stay in the upright position.

Ideas?

Posted by: euro911 Feb 15 2014, 12:06 AM

Bad relay?

Posted by: jcd914 Feb 15 2014, 02:47 AM

Could be the X circuit (accessory) in the Ignition switch. X circuit shuts down while cranking.With a failing ignition switch the X circuit may not get powered back up when the starter is released.

Jim

Posted by: Thestigz06 Feb 15 2014, 05:39 AM

I had a similar problem with mine, I found that I had a crack in the starter switch. After starting the car, try turning the key slightly back but not enough to cut the motor.

Posted by: Kirmizi Feb 15 2014, 09:53 AM

I'd start trouble-shooting at the ignition switch.
All sorts of funkiness can occur when they go bad.

Posted by: yeahmag Feb 15 2014, 02:35 PM

If the problem was with the switch I think I'd see other systems failing. Is there a relay that turns off the sub systems when cranking? The only thing that's not functional after starting is the headlights.

Posted by: Kirmizi Feb 15 2014, 10:35 PM

When my ignition switch was failing, the problems were intermittent and varied.
Just to try and narrow this down, no other circuits are affected?
Running lights, radio, etc... and does it happen consistently?

Posted by: yeahmag Feb 15 2014, 10:45 PM

The headlights seem to be the only circuit effected. Where is the relay that cuts the power to them when the starter is cranking? I'd like to replace that one for good measure.

Posted by: yeahmag Feb 15 2014, 10:50 PM

I should mention that the parking lights and dash lights DO work.

Posted by: jcd914 Feb 15 2014, 10:50 PM

There is no relay to turn off the accessory load, it all goes thru the ignition switch.
Pelican has the wiring diagrams in their site and you can trace out the accessory power from the switch to a couple different fuses. There should be something other than the head lights that are affected if the switch is failing but I would still check it first, since it is a common failure. The wiring to or from the fuses may not be connecting correctly. Since all the connectors at the fuse panel are standard spade connectors it is easy to put connectors on the wrong fuse connector.

Use the diagram to find the accessory wire fro the ignition switch and hook a voltmeter or test light and start the car, does it keep it's power?

I worked with a tech that constantly drilled me with "Test, don't guess" and "Work smarter, not harder", good advise (a bit annoying but good).

Good luck.
Jim

Posted by: yeahmag Feb 15 2014, 10:59 PM

http://www.914world.com/bbs2/index.php?showtopic=90030&hl=headlight++starter#

I think further up in this thread it mentions that the heater blower is affected by this circuit. Gonna go check that...

Posted by: Spoke Feb 15 2014, 11:00 PM

Wow. Awesome advice.

Measure the voltage across the headlight relay before and after you start the engine.

If you don't have a voltmeter, buy one. Let us know what you measure.

If you need help measuring, we can help you measure pertinent points.

Posted by: yeahmag Feb 15 2014, 11:22 PM

Yup. No go on the heater blower AND headlights AFTER going to the starter position. Guess it's time for a new switch.

Posted by: Porschef Feb 16 2014, 07:00 PM

If you need to replace the switch, it's an easy job, but most importantly, do yourself a favor and buy one through Porsche, they're still available and won't need replacement in 6 months like some of the cheap Chinese units.

Figger about 35 clams....

Posted by: Mblizzard Feb 16 2014, 08:30 PM

That is good advice. I replaced 3 of the cheap ones before getting a good German switch.

Posted by: yeahmag Feb 17 2014, 12:03 PM

Best price on an OEM unit I've found is $92. The aftermarket is $8. I've ordered both, but that is one hell of a price differential.

Posted by: ClayPerrine Feb 17 2014, 01:11 PM

But you will probably replace that cheap one 10 times before the OEM one fails.

Posted by: Mblizzard Feb 17 2014, 01:16 PM

I replaced the cheap one 3 times. Lots of work and down time compared to the cost.