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Lucas Smoke? Or the tale of mysteriously flashing turn signals.  Rate Topic 
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 Posted: 08-15-2005 03:35 am
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Joel
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i was walking by my car today - sitting quietly in the drive way. i had not run it for a day. and, lo and behold, the left turn signal was blinking away. it had come on all by itself. . .i played with the switch to no avail. i thought perhaps the problem might be there as the entire unit is loose and needs some sorting out (the ring used to tighten the unit is broken - I figured that out while searching for the source of the ghostly 'lucas smoke' that turned on my signal light).

anyway, i got the damn thing to shut off by unplugging the relay under the dash. it had been on for a while and was quite warm - ouch warm - to the touch.

my first thought is to replace this relay. any other thoughts? i'll call delta tomorrow to see if they have the relay. but, i figured you fellas might have some insight as to whether this is the problem or not.

i'm just glad i saw it flashing before it either melted some wires (the relay was HOT!) or ran the battery down. maybe i should buy some of the lucas smoke that was on ebay?

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 Posted: 08-15-2005 01:52 pm
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Mark Rosenbaum
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Having a flashing turn signal requires the ignition switch to be on and the turn signal switch to be engaged, or wiring failures to simulate the activation of both switches.  Multiple failures are not impossible, but are rare.  It's far more likely that the Hazard function was activated.  Were any other lights flashing?  If not, are any of those bulbs still good?  In what position is the Hazard switch? 

The 'relay' you mention should be the hazard flasher or turn signal flasher.  Either can be replaced with a generic US-made flasher of the appropriate sort (IIRC the type numbers are 552 and 555, don't recall which is which).  These round flashers are readily forced into the existing spring mounts for the rectangular Lucas parts.

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 Posted: 08-16-2005 01:44 am
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Joel
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Mark:

I think you're right. It is the flasher relay not the turn signal relay. Upon checking tonite - the turn signals work but the flashers are doing strange things.

So - I guess I'll look for a flasher relay. I think it's the relay (and not the switch) because it seems they work some of the time - and sometimes only one works.

I'm fine for right now - wire wiggling and thumping on the relay. . . - but if they wig out again i'll just try getting a new relay.

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 Posted: 08-16-2005 04:11 pm
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Mark Rosenbaum
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Thanks for the additional information.  I would conclude that your problem is almost certainly a defective Hazard switch rather than the Hazard flasher.  Usually the root cause is corrosion inside the switch.  This can create bizarre and ever-changing symptoms, including the blinking of Hazard/Turn lights even when the switch is in the Off position.  Note that all the Hazard/Turn lights on a side are normally wired together.  If only one light works sometimes, you have additional problems, probably in the socket of the non-illuminating light.  And any 'creative' rewiring by a previous owner can really confuse things.

Occasionally a Hazard switch problem goes away if one exercizes the switch a few tens of times.  This is usually only a temporary cure.  It is possible to remove and disassemble the switch, clean it out and lubricate the electrical parts with dielectric grease, then reassemble and return the switch to the car.  Unfortunately, a vital bit of the plastic switch body will often break during the process, and if this cannot be repaired, the switch must be replaced.

Virtually all of the original switches were used up many years ago, and any remaining survivors are now both rare and expensive.  Delta Motorsports sells an inexact replacement that works perfectly and seems far more reliable than the original, but which has male blade terminals rather than the male pin terminals necessary to mate with the car's wiring harness.  Delta provides suitable female blade terminals with their switch, but incorporating them requires modifying the wiring harness.  As far as I know, no one makes an adapter that would interconnect the wiring harness and Delta's switch.

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 Posted: 08-16-2005 07:50 pm
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Jim Ketcham
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British Wiring sells a hazard switch with the correct pinouts that match the JH wiring harness and can be plugged in directly  Unforunately, the switch body is just a bit shorter than the original.  The switch can also be wired to illuminate a small red internal light if desired.  Link > http://www.britishwiring.com/CAT18_19.PDF

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 Posted: 08-16-2005 09:18 pm
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Mark Rosenbaum
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Jim, you described the British Wiring switch as 'shorter'.  Is that less height, or less depth?  And do you have a measurement?

For what it's worth, my car's failed Lucas hazard switch (stamped 39868D and datecode 0387) measures as follows:
*  The switch body is 0.900" wide x 1.504" high x 0.831" deep from rear of bezel to rear of body.
*  The contact pins are 0.118"-0.122" diameter and protrude 0.375" beyond the rear of the body.
*  The bezel section is 1.033" wide x 1.539" high x 0.125" maximum thickness.

 

Last edited on 08-16-2005 09:18 pm by Mark Rosenbaum

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 Posted: 08-17-2005 05:19 pm
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edward_davis
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I'm curious, does anyone have a price quote on these replacement switches?  The PO superglued my original switch in the off position to fix the Lucas "smoke" problem, and I'm undertaking the slow process of making all of the electrical bits work on my JH.

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 Posted: 08-17-2005 07:10 pm
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Mark Rosenbaum
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IIRC, both Delta's and British Wiring's offering go for $30 or so, depending on exchange rates, availability, and for all I know the phase of the moon over Stonehenge, and the price of a pint of bitters in Birmingham....

It's my understanding that most British cars of the period did their turn signal and hazard functions the same way as the JH, so a switch from an MG, Jag, Triump, etc., would likely work the same way, electrically (though I can't guarantee this).  Mechanical fit might or might not be a problem.

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 Posted: 08-30-2005 12:53 am
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edward_davis
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I've ordered a switch from http://www.wiringproducts.com that should fit the JH hazard application.  It's a DPDT on-on switch, and I'm planning on wiring the "bottom" of the old hazard switch to one pole and the "top" to the other.  When it's in the lower position, the power will go in from my "turn signal" fuse and out to the turn signal mechanism, and the hazard circuit will be broken.  Whin it's in the upper position, the power will go from the hazard flasher mechanism out to the lights, and the turn signal circuit will be broken, just as in the orignal application.  If it works, I'll send pictures.  The switch seems to be the right dimensions for the JH, and it only costs $6.35 plus S&H.  If it doesn't work, I'll post that, too, so other folks won't make my mistake.

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 Posted: 09-25-2005 07:05 pm
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edward_davis
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Well, I've added my switch, and it works, but it doesn't fit the dash cutout perfectly.  There seems to be about a millimeter on each side, left and right.  The top-bottom size is fine, so it doesn't shift around.

I had to make a pretty radical change to my flasher circuit to get it to work though.  I've run both the hazard and turn signal circuits through a single flasher unit.  The power comes from the battery, through a fuse, to the flasher (formerly the hazard flasher) and into the switch.  Then the power either goes 1) to the turn signal switch or 2) directly to the marker lights through the original hazard wires.

I've posted pictures and more description on the Photo Gallery:

http://jhppg.com/gallery/album01

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 Posted: 10-20-2005 11:51 am
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Ron Earp
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Joel,

Once you let all the smoke out of the wiring harness all is lost.  At best you can get some replacement smoke but don't ever expect it to work as well as it did before the smoke escaped!

A nice primer for you:

http://www.peizhang.com/forfun/forfun_writings_smoke.htm

Ron

Last edited on 10-20-2005 11:52 am by Ron Earp

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