Cooking fuses

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Neal Zimmerman

Neal Zimmerman

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Ok, bear with me , this is a bit of a story. I will try to be concise.
1) Bought my 68 cuda, under dash wiring was a spaghetti bowl, found an uncut harness at Wildcat Auto wrecking.
2)No gauges worked so I went aftermarket and installed Mechanical oil pressure, tach, voltmeter, Water temp and fuel gauge.
3) I installed the O.P. gauge in the unused center hole of dash and the tach in what should have been ( I guess) a clock? The remaining 3 gauges hung under dash.
4) Did the Mad electrical bypass
5)Removed from the harness what seemed irrelevant, like wiring for factory gauges, heater (no heater in car), etc.
I was very careful when I did all this, didn't rush myself, felt I was thinking it all through before I made any move.
BUT I am worried that I awoke some demon of strange Mopar wiring oddities, because now the 20amp third fuse ( starting with INST/LAMPS) just keeps blowing. My diagram shows this to be Battery Feed, and my test light shows it to be always hot. Should that always be hot or is it regulated some way?
Neal Z.
 
The "battery feed" as such is not fused. I have no idea from your description what fuse this is.

You have THREE separate circuits (busses) in the box
1...The always hot buss. This is fed UNFUSED off the black ammeter wire, protected ONLY by the "fuse link" in the engine bay. It then feeds fuses which feed things like tail / park lamps, brake lights, etc, which work with the key off

2...The accessory buss. This buss is fed from the key ACC circuit, so it is only hot with the key in ACC or "run" and that feeds fuses for heater, radio, etc, which much have the key activated

3...The last one is a "trick." This is the INST fuse on one end of the panel. It gets power FROM the dash dimmer control, and feed TO the dimmer controlled lighting on orange wiring.

A way to troubleshoot shorts is to add a lamp such as a stop/ turn lamp in SERIES with the load, IE across the removed fuse, or in series with battery ground. Then remove loads on that circuit until the lamp goes out. First thing to do is figure out WHICH fuse this is and WHAT loads are on it, and these should be listed in the shop manual, before the diagrams begin.
 
In my 70 Duster with a 71 wiring harness, my horn circuit is shorted out and blows that fuse. As a “temporary” fix I just unplugged the horn wire from the steering column connector.
Unplug that connector and see if it still blows
 
Disconnecting the lighter, then is the FIRST thing I'd do. Actually either dome or lighter are excellent candidates "for a short"

fuses.jpg


fusepanel.jpg


Above, you can clearly see how the fuse panel is divided. The fuses are fed from above, the loads at bottom of fuses. Fuses to left are ACC. Third fuse from left is fed via a jumper. I think it is an option. Two fuses from next block to right are "always on" --and the ones you are dealing with. Last fuse to right is the INST lamp fuse.
 
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Cigar lighter is cut off, folded back and taped up, so thats most likely OK,. I suppose dome light could have issue or a wire leading to it.
Another thing I wondered about is that when I installed the emergency flasher switch connector I noticed there are two ways it can go on. Just four prongs in a square. I am wondering if its backwards or how you can even tell the right way it goes on.
Neal
 
Is it a fastback? The dome lights on the sides in the back have power to them all the time & the bulb holders can break & short to the frame.
 
67DART273 that last fuse ( right most) is what you were talking about right? The one you said was tricky. Feeds from headlight switch, goes to dash instrument lights. Wouldn't that only light up ( on test light) when you pull on the headlight switch. That's how I wired in my aftermarket gauge lights in my Coronet.
 
Disconnect your battery before doing ANYTHING with the pillar/courtesy lights on the FB. I just redid the rear harness on our 67 FB. You would be wise to redo yours. There is MINIMAL room to change those bulbs, etc. Also smash the f**k outta the bulbs and put in LED'S.
Good luck
Neal Zimmerman said:
Yes its a fastback. Thanks I will look them over.
Click to expand...
 
Sounds like in the re-wiring, maybe a mix up, but some components added to the cct & is now overloading the fuse.
 
if its your dome light that is the problem...you may find the wire up the screen pillar melted....

if so do not pull them out whithout tapeing new wires to their dash/ kick panel end so you can pull the new ones in......

before you put it all back. stick a pice of fibre board to the metal roof to act as a backing for the lamp. so that a person with a BIG head can't press the lamp connectors into the roof and short it all out again.

you may well find the original pice of card/fibre board floating about on the headliner

it really depends how High or Poverty spec you car is. in regards to the syle and implemention of the dome light and any anti- short circuit protection they put in... mine is a kind of bowed rectangular lamp and its basically crap, far too easy to short it out so i went to town with cling tape littl rubber boots for the connectors and fibre board.

Dave
 
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