XJ40 ( XJ81 ) 1986 - 1994

Intermittent tail light

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  #1  
Old 09-30-2017 | 07:12 PM
Lawrence's Avatar
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Default Intermittent tail light

As title says, I had a BFM warning and a tail light that was sometimes ok and sometimes not.

Replacing bulb made no difference but a wiggle of the socket would make the bulb "flash" on and off.

Cleaning the socket had no effect so I decided to melt the plastic retainers on the socket mount to remove the circuit board.

When I saw the circuit, it was pretty obvious what the problem was - both the running light and back up bulb connections were VERY starved of solder and the running light connection was cracked to boot.

A quick reflow of the joints and all was back to normal.

Not sure if I've encountered this issue before, maybe someone else had this problem in the past?


The rear bulb holder, driver's (LH) side

Tail light socket upper left, intermittent

Melting plastic nipples to release circuit board

cracked and starved running light connector at far right

reflowed joint

circuit board reassembled, plastic nipples re-melted.


Cheers

Larry
 
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  #2  
Old 10-01-2017 | 01:09 AM
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Larry,

Over the years I've had problems with tail lamps in our '93 that would stop working even though the bulbs were fine. I've cleaned the sockets and bottoms of the bulbs and pulled up a bit on the center terminal of the socket, and all has been well for awhile, but I think you've probably identified the real problem! Next time it acts up I'll follow your lead.

Thanks!!!

Don
 
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Old 10-01-2017 | 11:36 AM
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Must be a fault in production, those joints were very sparsely soldered!!

Maybe the QC guy was asleep (again!)

Larry
 
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Old 10-01-2017 | 07:14 PM
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Originally Posted by Lawrence
Must be a fault in production, those joints were very sparsely soldered!!

Maybe the QC guy was asleep (again!)

They must have been soldered by the same guy who did the BFMs, TCMs, ABS modules and fuseboxes. I wonder if his coworkers called him "The Solder Miser."
 

Last edited by Don B; 10-01-2017 at 07:16 PM.
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  #5  
Old 10-08-2017 | 09:00 PM
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Nice job. I've fixed so many things with a soldering iron. While these old XJs have a ton of relays and circuit boards the individual solder joints are huge and easy to fix.

I had a problem with my taillights just going out and not setting a BFW. The hardest part was figuring out which relay controlled them. When I found the relay and looked it up there was a core charge on the relay so I new it was repairable. 5 min with a soldering gun and done.
 

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