Topic: dash lights blowing fuse

[sflaten]

Does anyone have a lead on where to start looking for what is causing fuse to blow on 1969 Mach 1 dash lights. I have changed the light pull knob initially as the dimmer would not adjust and get to the top of range to illuminate speedo etc. Somewhere it popped the fuse. I got a second knob unit and had it fail again. Anyone had similar issue that might get me started.

[J_Speegle]

Would get a wiring diagram and unplug first item in the circuit and check, after putting in a new fuse. If the fuse doesn't pop,  pull the second item (if there are multiple items feeding in that circuit) plug back the first time and try it again. remember to operate what ever the item is at each step.

Work forward until you go through everything as well as checking the feed wire for cracks, grounding and problems along the way

Just what has worked for me

[67gtasanjose]

#1 cause of fuse blowing: Aftermarket or altered original equipment. This is true no matter what car you are working on.

First, does the fuse blow out instantly or after a while? If after a while, it may be more difficult to trace.

As Jeff mentioned, get a wiring diagram of where all the circuit goes, consider also anywhere a wire might get pinched (e.g., under carpet or floor console to auto shifter indicator, is always a possibility...if you have an "automatic" or have a "converted from automatic" car)

Richard

[CharlesTurner]

Possibly a shorted/pinched wire somewhere too.

[sflaten]

The fuse does seem to take some time to pop. I was hoping for a typical problem common to the cars to shorten the hunt. Do have the wiring diagram, so looks like it's time to stRt hanging upside down under the dash. To make it even more aggravating the fuse that is the problem is very hard to find. Auto stores only have them in an assortment pack where you only get one that you need and 6 you don't. Time to find an electronis house

[sflaten]

Thought I would post results so the next guy searching could benefit.

It looks like I found the source of the short in the dash lights. I pulled the pad, dash and looked all over behind the radio etc. Finally found an odd loose wire under the center counsel ash tray.  Looks like the wire going to the center contact in the lamp socket broke off the crimped on copper contact. I was able to pry open part of the crimp and solder it in place and recrimp. put it all back together and it looks like it is working. Was a periodic issue and had no pattern, so it looks like it was flopping around and only occasionally hit the ground surface.

FYI, this circuit used a Buss SFE4 fuse that only comes in a pack with many other sized fuses. No a good cost effective solution. Found Grainers has a 5 pack for sale

[67gtasanjose]

Thought I would post results so the next guy searching could benefit.

It looks like I found the source of the short in the dash lights.

 

[midlife]

I buy glass fuses in bulk: typically 100-200 of each type from an industrial supplier specializing in fuses.  I'm not your typical hobbyist when it comes to fuses, as I go through about 500 fuses of all sizes per year.

http://fusesunlimited.com/