Fuse bypass with blade ??

[GothingNC]

I am getting ready to replace my melted relays and the fuse board and have a question of why a bypass blade fuse was added by the previous owner.

The 25 amp ceramic fuse for the fuel pump is not installed and the wire is not connected to the top of the fuel pump fuse.

However, there is a wire connected to the bottom of the fuse pump fuse terminal connected to a 25 amp blade fuse and then goes to the top of the hazard light fuse terminal. (it is now a melted glob )

Looking at the diagram in the Bentley, the hazard and fuse pump fuse terminal share the same red power wire.

Any thought on why this modification was done and I'm wondering if the circuit overheated as a result of the fuel pump seizing and then turning on the hazards?

[billybek]

Sometime a section of fuse block will just go "bad". What caused it to go bad is really the question. Sometime carbon arcing to ground will cause a ground shunt that you should be able to see with a good quality ohm meter/ multi meter. Perhaps moisture or some other magical mixture could do the same. Excessive resistance through the block (bad connection) causing excessive draw and blowing the oem fuse? The bypass fuse could have been installed for these reasons.
Hey, this is my first reply!
Bill K

[GothingNC]

Bill ,

That makes sense.

I wonder why the Hazard fuse circuit was used instead of have the blade fuse wired to the top and bottom of the fuse pump holder and this resulted in an overload from the fuel pump going kaput.

I plan on replacing the fuse block and already have a fuel pump replacement relay socket with the full length of the wires and factory connections from the Pelican member Casey

[billybek]

That sounds like the way to go...
My first car was a 74 VW Thing... Crazy fun car.... for a box on wheels. I really enjoyed abusing it.
Good luck with your project.
Bill K

[GothingNC]

Originally Posted by billybek

That sounds like the way to go...
My first car was a 74 VW Thing... Crazy fun car.... for a box on wheels. I really enjoyed abusing it.
Good luck with your project.
Bill K

Bill,

I sold the Thing a few months ago

[billybek]

John,
Looks like that "Thing" was in great shape..
I started a new thread titled 'Billybeks New Ride' if you want to have a look at the "new" SC and where I went to get it.

[GothingNC]

Well I found out why the fue was bypassed - the original holders were broken.

Per the Bentley a red wire is supposed to be connected from the top of the fuel pump fuse and joined to the top of the hazard/backup light fuse.

I finally finished splicing in the new fuel pump relay socket along with the window relay and new by-pass blade fuse (20 amp quick burn) and decided to start the car to see what would happen.

1st turn of the key and she fired up plus my dash brake light/seat belt light works

Now I can go about replacing the 10-fuse block and double checking the draw.

Bentley manual states that the draw at the pump should only be 4 to 6 amps, but why is the fuse rated at 25 amp?

Original burnt parts



As it is now before replacing the fuse block



The black stuff you see on the red wire between the two relays is just plastic residue from the plastic ribbed wire covering for the stereo hookup that was running along the tob of the fuse box. I was able to scrape off with my finger nail.

[billybek]

Hey John,
Good to see you have most of that worked out..
I was just checking the wiring diagram to see if there were any other loads on that fuse.
Looks like the rev limiter, air flow sensor, output to tach??, output to power the coil on the oxs relay. Might be missing some other stuff.
Sometime fuses are oversized to accommodate starting inrush of a motor (pump) load.
Some pretty nice melted used parts you have there mister!

[billybek]

John,
Just saw a 73 Thing go for $29000. on Barret Jackson!!

[billybek]

I guess that was last January's show....
Still $29000.

[GothingNC]

I've seem them go for over 20k in pristine condition.

New paint, top, side curtains, etc really add up $$.

Here is a Thing listed for 25k

http://www.thesamba.com/vw/classifieds/detail.php?id=535248



Just finished replacing the fuse block and have it rewired back to stock and car started right up again

I took the stone gaurd off the pump and it looks like new and the connections are free of corrosion.

I wonder if the problem I had was caused by a bad relay (it looked old before melting) and the fire started from trying to restart the car with the hazards on since the fuse box wireing was tweeked?

[911pcars]

A penny for your thoughts and for old style screw-in type residential fuse boxes.

That is to say, the relay may have melted because the previous owner used a 25A fuse to mask an intermittent/partial short circuit that was opening the factory fuse. 24 amps flowing through a low-amp circuit will eventually overheat it.

The solution is locate the cause of the current draw. You might have repaired it with the fuse box repair, or not. Do you have a multimeter?

Sherwood

[GothingNC]

Sherwood,

I have a muilti-meter.

The fuel pump fuse holder was broken (bottom of holder snapped off) which is why the blade fuse was used to bypass.

It looks like blade fuse holder ignited which took out the fuel pump and window relays along with the sockets. I do not know what amperage blade fuse was used by the prior owner but it has been set up like this for about 6 years.

[billybek]

Fuse #16 required size is 25 amp. You do have a very valid point and when I re read the post it says that he is going to double check the draw, but not what the pump was actually drawing.