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Old 08-18-2007, 05:42 PM
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blowing fuses on headlights of a '32

I continue to blow fuses (30 amp) on the headlights of my '32. They seem to work when I idle or drive slow but out on the highway (50 mph) the fuse blows.
Any suggestions? Where do I start? Are the taillights and headlights on the same circuit?
Thanks.

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Old 08-18-2007, 06:16 PM
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Doc here,

Need a bit more info for other than guesswork..

Is this a kit harness?

A KIT light switch?

A FOOT Dimmer switch?

are the heads incandescent or high power blue or whites?

Do you have an alternator? and what is the output at an equivalent RPM at 55 miles an hour in Volts?

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Old 08-19-2007, 07:32 AM
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Doc.... here's the information as I understand...

This is a wiring kit. I believe it is a Ron Francsis. The steering column is a Flaming River. It does not have a foot dimmer switch. There is an alternator in the vehicle and the gauge seems to read 15 volts at all times.
Do you think it could be a loose ground from 'bouncing' down the highway?
But I don't understand electricity and I can't figure out why it 'blows' fuses.
Thanks for any insight.
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Old 08-19-2007, 06:40 PM
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Doc here,

The Very FIRST thing to do is VERIFY that the alternator output is 15 or above volts..you may be over charging and shorting out a relay or something..

Run the Car at a warm curb idle with ALL draws off or defeated..measure ACROSS the battery with an accurate DVOM, Set for DCV, 20 VDC or higher Scale...IF it reads above 15 volts at Freeway RPM's you are overcharging..and need some alternator service..(new diodes)...you MAY be doing damage to ELECTRONIC Linear Devices in the car...(AC on a DC source line)

A DC relay will "Chatter" with a volume of AC in it's power sources..this can / will blow fuses..check that too..

Always set up a good ground buss system when installing a kit..EVEN a first class kit does NOT provide them...

For your Ground Buss, Set it up as follows:

BE sure First, You have A 4 gauge Cable (for stock battery location, OR , 0/0 or 0/1 Cable for a trunk location) from the battery, to any handy bolt at or NEAR the starter on the block .

Using a short run to something like a seat belt bolt, or body bolt just adds resistance, the body is insulated..(has road paint and sits on rubber mounts) this , makes for a "Poor or no" Bonding situation..
  • that makes resistance..
  • Resistance makes Heat..
  • heat melts things and further insulates the bond,
  • which makes more heat..and so on..until you no longer have a good bond..

To install a proper ground buss system, This MUST be done:
  • 1 ) Run a properly gauged (0/0 or 0/1) Ground cable from the battery in the trunk, Or A 4 Gauge cable for a stock located battery, to any handy bolt at or near the starter on the block. From that same bolt get a 4 gauge Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame. Make this run as short as possible.

  • 2 ) Next get some 10 gauge wire and ring terminals, run two wires from your bolt on the block, to the Firewall, Burnish off all the paint, grease or oil or dirt from the area, Install a sheetmetal or Self Drilling Tech screw using a star washer as well as a lock washer.. and the other 10 gauge wire to the Alternator ground lug, bracket or mount bolt and attach with star and lock washers.
  • 3 ) Next get some Wire Braid, (expensive! about $10 for 5 - 6 inch pieces! ) Check Radio Shack for this, OR cheaper yet, get some RG 8 Coax cable, about 10 feet. Should run you about 15 cents a foot.

HOW TO MAKE WAY DURABLE CHEAP GROUND BRAID:
--------------------------------------------------
  • 1 ) carefully Slit the insulation from the cable with a Talaban Boarding pass (box knife) .


  • 2 ) Peel away the insulation until you just have the center dielectric and braid left, then carefully press the ends of the coax cable BRAID together like a Chinese "Finger puzzle"


  • 3 ) Slide the dielectric and center conductor out. remove it and toss it..


  • 4 ) On a work bench, Flatten the Braided shield out, use a round weight like a full paint can to roll over it.
------------------------------------------------------

This will be your braid cable, just Cut to smaller length's as needed, and tuck the cut ends into a crimp terminal and crimp the ends on..

IF you can Solder, Tin the ends before you tuck the ends of the cable into the terminals, then Tin the barrel of the terminals, then insert the cable and crimp..

Then heat the terminal and braid, feed some solder into the opposite end as the heat is being applied, let it melt and FLOW or WICK toward the heat..until the terminal barrel is filled and is smooth and shiny..

that is a good joint..gray and rough is a "Cold Joint" and you'll have to start over..
  • 4 ) NEXT, install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body. Install a cable or Braid From the Fuel tank Ground lug where the sender, Fuel line is to the frame..burnish the frame, use star washers and sheetmetal or Tech (self Drilling screws) on the frame.

  • 5 ) At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.


It sounds like a lot of work, but after you assemble all the parts, it's only a few hours to do..and you'll end up with a system that will work reliably for many years to come..and can eliminate that from your troubleshooting list.

Remember: GROUND is the other Half of your 12 volt circuit AND is equally as important as having POWER to the device!

Do this Regardless of what you find!!

High low beam relays (loose or "Chattering" ) will cancel headlghts AND blow fuses..

Headlamps usually ARE not on fuse busses..the head lamp switch usually has a thermal reset right on it , measured for the ampacity of the lighting system..if it gets too hot (short) the reset opens until cool, then closes again..you may need a device such as this, OR your fuse/wire may be under rated..



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Old 08-19-2007, 09:33 PM
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Another angle?

As always, Listen to the Doc as he knows what he's talking about!

Now, as a guy who has troubleshot for many years, I have seen a lot of weird stuff happen.

I'm wondering if that difference of only happening at 50 mph might be a vibration related matter? Wiring chaffing, closeness of a connection to a ground, rubber grommets missing where wiring goes through?

I'd make a physical inspection with vibration in mind.

Steve
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Old 08-20-2007, 07:49 AM
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DOC,,,,
Thank you for all the information. I will start on this and hopefully I can resolve the problem
Again, thanks
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