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 Blowing #4 Fuse

 Created by: Mini41
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 Posted: Mar 25, 2017 10:32AM
mur
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It is great that you followed through. 

There should be a ground wire in that harness that is fastened to the speedometer. You can always subtlely and neatly add another, going straight from the speedometer back to the body of the car. Also, at this point, carefully check the main front harness to ground point. Perhaps paint is preventing a good connection.

 Posted: Mar 25, 2017 09:31AM
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Chalk another success up to the forum members willing to help an electrical system dummy.

geoO suggested that the tail lights might also be involved with fuse 4 and they were indeed not operating.  I did't pay any attention to them because the brake lights had been working and were staying on when the I turned the headlight on because I had not yet adjusted the brake light switch on the brake pedal. I took those for tail lights even though they were a bit bright. DOH!

After figuring that out I began looking around the tail light wiring and found a splice in the only wiring I didn't replace back there - the ones going to the license plate light.  I opened up the light fixture per nkerr's suggestion concerning a possible devide fault and found a dangling wire like Dan Moffet mentioned that was causing the power and ground to be in contact with one another.  Thus a short to ground and the blown fuse.

But when this was sorted out I still only had instrument lights and no speedo illumination.  As I mentioned, the instrument lights had ground wires but the other panel lights did not.  So I grounded these two and - SHAZAM - I had all the panel lights.

So the bottom line on all this part of my electrical woes is that the wiring harness I bought to connect the center cluster I switched out on my '84 saloon (which had a three clock set up) was not correct and needed some assistance.  Only one indicator light on the speedo had a ground as well and I needed to add to the other to make them both flash.
I guess there might have been a central ground wire somewhere in that harness that I failed to connect.  But I sure didn't see it.  

So I'm back in business.  Sorry for the long explanation but I often see other forum members asking original topic creators if they ever solved their problem and how.  So I did the same.

My sincere thanks to all.

Jack

 Posted: Mar 25, 2017 05:54AM
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US
You might check your taillights too. When I was blowing that fuse, I lost panel lights AND taillights.

 Posted: Mar 25, 2017 04:52AM
 Edited:  Mar 25, 2017 04:53AM
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"The question is, is there some obvious problem that might be causing me to keep blowing the #4 fuse?"

yes and no

yes, there is definitely a short to ground somewhere which is causing your fuse to blow

no it might not be obvious - usually with old wiring you will be looking for frayed insulation, a bare metal edge of a body hole somewhere that is cutting through a wire (missing rubber grommet), things like that.  But, you've indicated your parts are all new.  In that case, I'd suspect a mistaken connection made somewhere while installing the new harness.  


Note that only wires that are the same color will ever be connected to each other.  If you have, say, a black wire connected to a red one, that will definitely blow a fuse.

Inspect each of the places where wires are connected to each other and make sure only same color wires are connected.  If that all checks out, make sure the only color wires which are connected to the body are the black ones.

If those things all check out, then there is a possibility that one of your devices has an internal failure, shorting to ground.  Maybe a new part was made wrong?


You can narrow down your search by studying the wiring diagram and only looking at the things which are run to and from that particular fuse.  IIRC, maybe that fuse only manages dash lights and the side marker lights?




hope this is helpful!
N

 Posted: Mar 25, 2017 04:43AM
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CA
Any after-market gauges (e.g. a tach) or illuminated switches that may have been spliced into the illumination circuit? Have any such previous additions been removed, leaving the illumination wire dangling? 

.

"Hang on a minute lads....I've got a great idea."

 Posted: Mar 25, 2017 03:25AM
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After working out a problem I had with the red ignition/battery light on the center cluster set up in my '84 saloon, (thanks to kind forum members) I have all lights working as they are supposed to except the panel/instrument lights which keep blowing fuse #4 on my fuse box.  The speedo illumination lights run off of red/green wires and the oil/temp illumination likewise come from red/green wires with added black ones.  The red green wires mentioned terminate on the opposite side of the fuse box from where a solid red wire attaches.  These are positions 7 and 8 on the box.  All wiring is new as is the fuse box.  All fuse box connections are as they are suppose to be and I have a nice fat cluster of black ground wires that come out of the main harness are are firmly and cleanly attached to bare metal on the inner fender.

 

The question is, is there some obvious problem that might be causing me to keep blowing the #4 fuse?

Jack