Any advice as to why the small 4 amp SFE fuse on my 70-442 continues to blow as quickly as I insert it into the fuse box? I have owned this car for 5 years and have never experienced this issue until the last week or so. Right before this issue started I had disconnected both battery cables in order to take the alternator off and confirm the build date stamp (which on an a/c optioned car is on the underside of the alt). I replaced the alt and cables properly and now have this issue. The small 4 amp fuse is the fuse located at left side bottom of the fuse box and feeds the instrument cluster lights and console light. Also, right before this started I engaged the heater to make sure it was still running properly and at first it blew nice and hot then the air temp went nuetral. No other fuses are blowing. Any ideas on what might be causing this issue would be appreciated.
Jeff

 

Yeah. You've got a dead short.

The hard part is figuring out where.

I'd probably start at the headlight switch and work outward, but you may end up removing all of your dashboard lights before you find the one with the nick in the insulation.

A quick and dirty way of finding a short like this is to replace the fuse with a piece of copper wire - hold it in there for a few seconds, until something starts to smoke, then go to where the smoke is. Not for the faint hearted, and you could end up replacing a bunch of wire (or the whole car) if you try it.

- Eric

 

Usually this can be related to the last thing you did to your car. Are you sure everything was put back as it was?

 

Truer words were never spoken, but if all he did was on the other side of the firewall, none of it could be related to that circuit (so long as the car is wired as stock...).

- Eric

 

Yep a dead short to ground. If this occurred immediately after moving the heater controls look on the back of the heater control to see if the temp lever cable pinched a wire to a lamp and at the other end of the temp cable to see if the mechanisms at the heat blend door pinched a wire when moved. Something in these areas happened because the temperature when neutral also. IIRC these wires are purple or gray. Keep us posted.

 

A mechanic tried the copper wire trick on a car I owned and fried my wiring harness.

 

I'd check the wires behind the alternator, it feeds to the regulator, or feeds directly to the gen light. I believe it runs off the lighting circuit powered by that fuse.

 

Thanks again

 

Nope. I can't picture the entire circuit, but I believe that the Alt light is powered through the alternator on one end, the ground, and the same circuit as the windshield wipers on the other end.

- Eric

 

I got to thinking after I posted that and the gen light is looking for ground or equalized power. So that might not be it.

 

This sounds like a sure-fire way to burn up the car, the garage if the car is in the garage at the time, and the house if it's attached to the garage.

What you need is this:



I had the exact same problem with my '73 Custom Cruiser, but it was with the taillight fuse. The moment I would pull out the headight switch, which also turns on the taillights, the fuse would blow.

This device is a fast-acting circuit-breaker that you clip to the two ends where the fuse would be inserted. It continuously resets, trips, resets, trips, etc. very, very quickly. The current is never left on long enough to cause a problem, but the oscillating nature of the current sets up a varying magnetic field along the wire. You hold the gauge part in your hand and move it along the wiring, even if the wiring is under the carpet or under the dash or wherever. At the point of the short, there is a break in the oscillating current, and the gauge senses this and wiggles. There is also an audible signal that changes pitch. That's where your short is.

It's really quite ingenious, and it helped me find the problem in my car, which turned out to be a pinched wire behind the taillight housing.

Yes, it costs $50, but the shipping is free, and it was worth it to me because, if I didn't have it, now four years later, I'd probably still be looking for the short.

 

That's cool! Definitely beats afried harness.

- Eric

 

Or worse!

 

Good tip Jaunty. Here is one about $20 cheaper

http://www.opentip.com/index.php?ref=664247

Always good to save a twenty spot

 

Interesting. It's the identical thing but for half the price (plus shipping, about $5 when I put in my zip code).

 

Yep and Summit sells it for around $30 + the ride.

 

I ordered mine today total of $30.71 shipped. I am going to put it through a test when it arrives

http://www.opentip.com/index.php?ref=664247

 

A while back someone here had their console harness pinched at the front of the console. Something to maybe check if possible.
Yes, I would check around the heater control area first. The 4 amp-er ran only the dimmable lights, to that should give you a hint of which ones to check.
Do you have the floodlights that lite up the heater and wiper switches?