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Thread: Mystery electrical problem

  1. #1
    Join Date
    Jan 2020
    Posts
    96

    Default Mystery electrical problem

    I have a really crazy electrical problem.

    When I turn the key to the run position and test the horn, emergency blinker and turn signals they work like a charm. If I start the car they will stop working after a while. Since the horn is on a different relay than the blink relay used by the emergency blinker and turn indicator it must be either an electrical supply problem or a grounding problem.

    When it is close to failure the horn and flashers will work intermittently and I can hear the relays buzzing instead of clicking. When they fail there is no sound from the relays.

    Strangely the head light switch works fine all the time and I can switch between high and low beams with no problem.

    My problem is that I can't find the chassis grounding point for the instrument panel. Will appreciate if someone can tell me where it is.

    The car is a 1987 1700 Supersprint. It is a mix of a pre-1988 and post-1988 1700.

    Thanks/Anker
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

  2. #2
    Join Date
    Apr 2018
    Location
    Ft Lauderdale
    Posts
    136

    Default

    Mine used the (unused) windshield washer bracket and then although you cant see it ran to central branch
    Name:  Grounding Point.jpg
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    Name:  Grounding Point 2.jpg
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    Life Can Be Cruel

  3. #3
    Join Date
    Jan 2020
    Posts
    96

    Default

    I'll check that, thanks. The one in the engine compartment was on the oil cooler bracket. Really hard to see!

    Jonathan from Lotus7.club has been helping out. Still haven't isolated the problem and suspect that it isn't a grounding problem, but something else.
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

  4. #4
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,335

    Default

    If it stops working after a while, it could be heat related. A failing connection can go intermittent as the joint expands from heat. After you shut of the car, does it take a while for those items to start working again correctly? If so, I'd be tempted to remove the scuttle and carefully use a heat gun on suspected joints to see if you can track it down that way.

    -John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  5. #5
    Join Date
    Feb 2012
    Location
    Roswell GA
    Posts
    972

    Default

    With noting the age of the car, many connections are plugs and sockets. There is corrosion that will build up over time. My example are indicator lights in instruments and on the dash. The lights were not coming on. Upon examination, the bulb(s) were fine, reinstalled, working. Simple unpluging and pluging back can have enough friction to burnish the contacts.
    Also, John's suggestions sound good.
    Life happens while you're making other plans
    1995 Caterham Crossflow RHD
    1990 Miata
    2007 GMC Sierra WT
    2013 Mini (Her's)
    2014 Outback
    JOHN DEERE D130

  6. #6
    Join Date
    Jan 2020
    Posts
    96

    Default

    Solved!

    It turned out not to be a grounding problem. By tracing all connections to and from the horn and the indicators/emergency flasher I found that the only common point on the power side was a connector on the alternator. Cheking that I found that it was loose and needed to be pushed fully in. Another connector was also loose and needs a pinch to have it go on tight.

    The previous owner had lived with this problem for a long time and no one had been able to fix it.

    On to the next issue. I have to get the distributor out and move it a tooth so I have the full range of advancement. Is it possible to get it out without removing the carbs? If not, it looks like I have to drain some coolant because the heater return hose goes to the intake manifold and I am not at all excited to take the carbs off the manifold again. It was hard work to get them on and the manifold nuts tightened just the right amount. So if I have to I'll remove them with the manifold.

    Electrical problems are the worst!

    Phew/Anker
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

  7. #7
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,335

    Default

    I'm curious, what is the max advance you can get without clocking the distributor?

    -John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  8. #8
    Join Date
    Sep 2005
    Location
    St. Louis, MO
    Posts
    455

    Default

    I've taken my distributor out on my Crossflow without removing the carbs/manifold. Lucas distributor?

  9. #9
    Join Date
    Jan 2020
    Posts
    96

    Default

    Yes, it is the Lucas with the Lucas electronic ignition module.

    I can get about 10 degrees and it still spits out the carbs. Before I worked on the carbs and distributor I had it at 12 degrees and it was happy there with no spitting and a smooth idle.
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

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