OT: Weird modern headlamp problem

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Model T Ford Forum: Forum 2018: OT: Weird modern headlamp problem
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Monday, September 24, 2018 - 09:58 am:

I'm almost embarrassed to post this, as there must be a simple answer, but it escapes me.

I replaced the low-beam headlamp in beloved's 2006 PT Cruiser a couple months ago. Yesterday it was out again. I procured a replacement bulb, installed it and... nothing.

The bulb is good and lights up on the battery charger (the old bulb looks OK but does not light up on the charger).

I get an 11.8ish volt reading across the headlamp socket when the lights are turned on, and zero volts with the light switch off.

An 1157 bulb does not light up when put across the socket terminals (temporary, see photo) but does on my battery charger.

So, I have a good bulb, apparent power at the socket, but no light!

This seems so simple — what am I missing?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James G Fisher III Peachtree City, GA on Monday, September 24, 2018 - 10:10 am:

You got a true mystery. I'd look at where the lamp itself plugs into it's holder. Other than that you might need a new holder. Just guessing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Baudoux Grayling Michigan on Monday, September 24, 2018 - 10:11 am:

You'll have to clear the code from the "TIPM", or Totally Integrated Power Module. I didn't believe it either. I've been certified as a master mechanic for over 35 years. It gets harder to stomach every day.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Monday, September 24, 2018 - 12:08 pm:

You’ve got a voltage drop somewhere in the harness going to the headlight. Check the voltage at the light while it’s hooked up and supposed to be on and there will probably be “0” volts. Your socket should be battery voltage without a bulb which your 11.8 volts would be well below a desired open circuit voltage at the battery of 12.6 volts or higher. You my need to find a wiring diagram to see if there are relays, plugs and other places where the voltage drops can occur which also includes corroded and damaged wiring.


Top of pagePrevious messageNext messageBottom of page Link to this message  By dale w on Monday, September 24, 2018 - 02:32 pm:

Those female sockets may be now be deformed enough so that you are not making good enough contact with the male "pins" in the headlight bulb.

You could still get a good reading with a test probe, or even jamming some wire leads into the female ends, but not enough contact with the actual bulb to allow sufficient current to flow.

Take a good look at the plug's electrical contact surfaces and compare it with another on your car. You can use a small dental pick to bend the metal blades to close up any out of spec gap so you have the correct amount of "pin drag"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brian Mettling - Dayton OH on Monday, September 24, 2018 - 02:37 pm:

Had the same problem, thought it was the TIPM too. Turns out it was a bad ground wire that got disconnected. Google your wiring harness, there should be multiple ground offshoots throughout the harness.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Monday, September 24, 2018 - 02:50 pm:

Thanks all for your suggestions and comments. I will report back after having another go at it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dean Kiefer - Adams, MN on Monday, September 24, 2018 - 06:01 pm:

Some car head lights have right and left fuses. But then you have voltage with the switch on. Must be some other thing?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wilson, Saint John NB, Canada on Monday, September 24, 2018 - 06:52 pm:

I had a faulty DRL (daytime running light) module give these symptoms on a Honda CRV.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hanlon N.E.Ohio on Monday, September 24, 2018 - 06:57 pm:

Check for a wire corroded under the radiator.
Seen it before on a couple PTs from parking curbs tearing stuff up. Voltage is definitely low.


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