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Posted by: Gunn1 Jan 6 2017, 12:17 PM

Members, my 73 914 has a issue I cannot seem to figure out.

While checking the frunk wiring harness everything appears to power up and work just fine, with the exception of the left wart. I had the same issue on my 2009 GM 1500 pickup. I could replace the parking/running light every day on that truck and without fail it would be blow out by the next day. Same thing with the left wart on the Teener. It doesn't blow/go out in front of you, but shut it off and turn it on the next day and dead. Replace the bulb and your good to go until the next day.

What could be going on here, I'm perplexed, but that comes easy for me.

Posted by: 914Sixer Jan 6 2017, 12:28 PM

Wire is going to ground somewhere.

Posted by: Coondog Jan 6 2017, 12:29 PM

I hear you on the Chevy truck, same issues. As for your Teener, take them off fill the hole and gain 15 hp from less side wind drag............

Posted by: Larmo63 Jan 6 2017, 12:52 PM

You can do what I did, just run a new black (stealth) wire to it along the wire harness, and tap back into the proper connection. It took me all of about a half hour to do, and it worked.

Easy peasy.

Posted by: Gunn1 Jan 6 2017, 02:21 PM

I do understand that however I'm not sure the ground or lack there of is the problem.

When the bulb on the wart goes out I mean it really goes out. Upon checking the bulb the filament is totally burned out, almost like a fuse. Could it be there is a stray voltage surge that pops the bulb?

I will try Lawrences fix and see if anything changes.

Posted by: Front yard mechanic Jan 6 2017, 05:03 PM

On my chevy it's the short loop/ line

Posted by: Mueller Jan 6 2017, 05:16 PM

Weak springs or contacts for the bulb. Or wrong wattage bulb?

Does the right side bulb match the left side? You could have had the wrong bulb the entire time.

Posted by: Rand Jan 6 2017, 05:52 PM

Posted by: Spoke Jan 6 2017, 06:24 PM

Most likely this is the case although it's likely not so stray. My buddy had I think a Suburban that always blew out the one front driving light.

The surge could be when you turn OFF the lights as the inductance of the wiring and load (headlights) can cause an undershoot.

When you turn on or turn off the lights, a step function of voltage is applied/removed to/from the wiring. The inductance of the wiring (all wires have inductance) causes an overshoot.

Below is Pulse 1 from ISO 7637-2 automotive standard for removal of power from a circuit with an inductive load like headlights. An inductive load resists a change in current. When current is removed immediately, the current in the load powers the circuit.

In Figure 5 below, Pulse 1 from ISO 7637-2 causes the negative going overshoot. UA is battery voltage of nominal 12-15V. The undershoot US is upwards of 100V.

Solution would be to check all wiring and your light switch. If your light switch is making/breaking with some jitter (on-off-on-off) as you move it, it could cause multiple Pulses 1 as shown below.

In ISO 7637-2, Pulse 1 should be applied 5000 times to verify that the unit under test passes the standard.





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Posted by: Gunn1 Jan 6 2017, 07:22 PM

I like the "Fast acting" part. Did go out and just ran a wire from the ground on the battery to the wart, pulled the switch, the bulb lit up, pushed the switch off turned on again, no light bulb was fried already.

Going to check the other suggestions tomorrow, shutting her down for tonight already 6 below here and supposed to get to minus 12 and that's real temp not windchill factor.

Posted by: ssuperflyoldguy Jan 7 2017, 12:13 AM

Try a different bulb base