Short Circuit Murphy's Law, do it now

[Rancho Deluxe]

This was initially posted in a thread on troubleshooting wiring (Miss Elizabeth popping her fuse!),but now I think it needs its own thread. Lots of us may have this defective part installed and ready to fail. You can fix it, so read on.
Here’s my short circuit story. Just a few days ago my 1930 fordor stopped dead on the highway. It has 2K miles on a complete restoration and has been owned by me since 1956. Lots of trips with “adventures” but never before has this car left me totally disabled on the road. It happened after passing thru a brief but intense rain squall. After numerous roadside checks I could not find the short, so with darkness near, I used my auto club towing service for the first time ever. No fun, but the operator acted like he towed 80+ year old cars every day.
I needed two days to sleuth out the problem with a multi-meter, wiring diagrams, and expert interstate advice. Just about everything got checked. The flaw turned out to be in what you’d least expect – the one part intended to protect all the rest from short circuits. My fuse holder is a recent item from a parts house (can’t remember which one). It has a badly flawed design and differs from others I have seen. The car wiring end, not the battery connection end, has a bolt fastened thru the sheet metal bracket and the actual fuse holder. See the photo. Three small plastic washers insulate the bolt and first nut from the sheet metal. Less than 1/32 inch clearance is there between the bolt head and the nut sides and the bracket. Somehow moisture, a small amount of corrosion, dirty engine compartment dust or crud, or something shorted this fastener to the bracket and thus the car. When wiring was disassembled for checks the short was not observed. Upon reassembly the fuse would blow. This bolt and insulator design is just a temptation to Murphy’s law.
All of us using a fuse device should check for this flaw. It’s easy to fix. Just cut off part of the bracket with the bolt mounting hole and fasten the bolt and car wiring only to the actual fuse holder, itself. It would be helpful if someone with the older fuse holder without this basic design flaw would post a photo to remind everyone what they look like.
Good Luck, Rancho

 

[C26Pinelake]

What do you mean by a Temptation to Murphys Law? Did you not have an experienced Model A person or mechanic to assist you with diagnosis ? Wayne

 

[Patrick L.]

Hmm, I'll be darned. That is different. Good catch. Looks like a good fix.

 

[clo2jim]

I like the use of the shorthened tie-wrap on the fuse to be able to remove it easily. I have the same things on all my Model A's

 

[SeaSlugs]

I want to say my recently bought fuse holder had the 3 washers but one fit JUST inside the metal to keep the bolt centered and the outer two to keep the nut and bolt from touching the plate....

also i like to take all the stuff off the mounting plate and paint it black - helps it blend in better and appear a bit more factory like.

 

[Jim/GA]

This exposed style fuse holder has been the source of more engine problems while I have been out on tours with others that I recommend you don't use them. Exposed to oil, dirt and water under the hood corrodes the little spring clips that the fuse pops down into, creating resistance that "comes and goes" (very hard to track down) and your engine starts missing. The engine vibration also loosens up the little clips over time. Now this short circuit risk (I had not seen it before) adds to the list of reasons not to use it.

There are fully enclosed, weatherproof "flat spade type" fuse holders out there rated for 30 amps (more than enough for most cars) that can be installed in the solid yellow wire that comes off of the starter switch. Solder the wire connections when you splice the fuse in and put waterproof shrink tubing on them. You will have a much better, more reliable fuse.

I will admit, you can not put a tie wrap around the fuse and remove it when you park the car as easily as you can the little round fuses. If the round fuse was inside the car, out of the weather, I could live with it. But exposed under the hood creates problems.

 

[Dick Steinkamp]

This exposed style fuse holder has been the source of more engine problems...

X2. It could be we hear mostly about problems here, but it seems that these additional fuses at the starter cause more problems than they solve. In addition, aren't the light and horn circuits still not protected if the short occurs while the engine is running?

If you must have one, I'd sure go with Jim's suggestion...