Author Topic: Brake lights  (Read 1039 times)

Offline don berg

  • Posts: 60
  • CLC Number: 20417
  • Name: d berg
Brake lights
« on: August 08, 2015, 10:35:28 AM »
I have a 1941 Cadillac 6267D When I step on the brakes the ammeter will go almost all the way to the left, the neg. side. Is this normal or do I have a short somewhere?  I took the brake bulb out one side at a time but did not make any  difference . Please help  Thanks Don

Offline TJ Hopland

  • Posts: 10188
Re: Brake lights
« Reply #1 on: August 08, 2015, 10:50:00 AM »
No other electrical loads seem to have that effect?   Is this car all stock?   No halogens or LED's?  6v?

Do these ammeters have an actual shunt in em or is it the typical where they are using the wiring or part of the regulator as the shunt?  A real shunt is hard to 'fool' but cars didn't seem to use real ones very often.   The 'fake' ones are pretty easy to fool with connection and grounding issues. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Offline Jeff Rose CLC #28373

  • Posts: 2324
  • CLC Number: 28373
  • Name: Jeff Rose
Re: Brake lights
« Reply #2 on: August 08, 2015, 10:57:56 AM »
I'd bet you have a bad ground and/or bad connections.  You can clean the ground and/or just run a jumper wire from the battery to the bulb and then see if you have the same result. 
Regardless of the result, I would take all the bulbs out and clean the sockets.  I'm sure there are better products out there but I just used contact cleaner and scotchbrite on the end of a screwdriver.  Clean the socket well and then flush it out. 
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Offline Steve Passmore

  • Posts: 5768
  • Name: Steve Passmore - Sadly Deceased
Re: Brake lights
« Reply #3 on: August 08, 2015, 04:52:24 PM »
Try connecting the two wires together on the brake light switch. If you still have the discharge that will at least eliminate the switch but it could be that which is shorting to earth.  Failing that the supply to the brake lights have to be earthing somewhere. Check all the cables to the rear lights to make sure they haven't chaffed through somewhere.

1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe

Offline Glen

  • Posts: 2789
  • CLC Number: 727
  • Name: Glen Houlton
Re: Brake lights
« Reply #4 on: August 09, 2015, 02:27:08 AM »
Do the brake lights come on as they should?  Try it with no bulbs.  If the ammeter still goes negative with no bulbs in you have a shorted wire.  Look for wires with insulation broken or worn off and touching metal.  The bad spot will be somewhere between the brake light switch and the light bulbs. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

Offline don berg

  • Posts: 60
  • CLC Number: 20417
  • Name: d berg
Re: Brake lights
« Reply #5 on: August 10, 2015, 10:42:19 AM »
Thanks guys for all the info. I will run the test and see if I can find the problem.  Don


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