Can't stop blowing these %$#@ fuses

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Can't stop blowing these %$#@ fuses

Postby 66 Sprite » Mon Oct 20, 2008 4:28 pm

So I'm getting dangerously close to having my 66 Sprite up and running. I spent some time the other day chasing down some little electrical demons (headlights, panel lamps, etc.) Prior to all of this, the car started up just fine, but now I blow a fuse every time I try to start it. It looks like something I did under the dash has caused this.

The symptoms: The fuse blows as soon as the fuel pump starts running, which is to say when I turn the ignition to accessory mode.
Most everything electrical works (wipers, tach and left blinker don't, but I believe those are all mechanical issues) when the fuse isn't blown except the brake lights (which had worked previously). I'm not sure if the brake lights and the fuse issue are related or not.

The only change that preceded this was rearranging some of the wiring under the dash to get the headlight switch and the panel lights working. I'm going to try to double check all the ground wires to make sure I didn't knock one loose. Any thoughts on the likely culprit?
Ryan R.
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Re: Can't stop blowing these %$#@ fuses

Postby Hey Mikey ! » Mon Oct 20, 2008 5:19 pm

I also have a 66--If there is one thing I learned about electricals is the fact previous owners have done their own "Maverick" wiring to bypass/rig problems instead of fixing them. When I startd on the bad wiring issues--many which were dangerous-- and started reconnecting-- just like your scenario--I usually made problems worse. Lights/horn, etc are always directly connected to the + battery side. (Neg Ground/chassis set up) When you throw a switch/make the connection--(lights, push horn) it is connecting the "other side" of that lamp/horn to chasis ground--completing the circuit. Most likely you have a short to chassis--a hot wire touching ground/chassis. A big culprit is the headlight wiring harness connection at the front of the car--mine had some missing insulation--just a bit to rub on the chassis and cause a short. As soon as I turned on the lights--blown fuse.
Do you have a Volt/continuity meter? You can test wiring to see if it is shorting or there is continuity to GND/Chassis when your switches are in the Off position. When switches are in Off position there should not be a connection to chassis/Battery GRND.
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Re: Can't stop blowing these %$#@ fuses

Postby Bugzy59 » Mon Oct 20, 2008 8:29 pm

I had a few shorts in my bugeye harness - mostly due to my wiring mistakes.
Your harness is more complicated than a bugeye but there are a few things you can try. I take it you do not have an ammeter. I was able to use mine to determine when the short occurred and thus isolate the problem. The ammeter needle pegged when the circuit with the short was engaged.
There are really three harnesses with the bug. The front, main and rear. I disconnected one and then determined if the short appeared. Then the other. While you have it disconnected you can use a circuit tester on the positive bullet connectors to see if there is a path to ground.
Good Luck!
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Re: Can't stop blowing these %$#@ fuses

Postby LittleRedMG » Mon Oct 20, 2008 8:56 pm

I feel your frustration. I have had my midget for about 2 weeks and i am about to replace ever wire in the thing. No sense putting lipsick on a pig ya know? I want to make sure that i never have to fix electrical problems again! (wishful thinking I'm sure!)
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Re: Can't stop blowing these %$#@ fuses

Postby hoggie » Mon Oct 20, 2008 9:11 pm

Are you using the original Sprite MKIII wiring harness ? Did you do a negative ground conversion?
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Re: Can't stop blowing these %$#@ fuses

Postby 66 Sprite » Mon Oct 20, 2008 11:42 pm

The update: I started with the connections in the brake lights and they were getting no juice. Next I checked the brake light pressure switch. It wasn't putting anything out either.

I took Hey Mikey !'s advice and started looking for shorts and/or wires touching the body. I found the ground to the tachometer was loose and then thought about the left front turn signal (which had a burned out bulb). I put in a new bulb and it still didn't work. took it apart and lo and behold the insulation where the wires run into the metal assembly was gone. Plus, because the insulation was gone the two prongs were touching. I remedied that problem with a $2.99 replacement wiring pigtail from Autozone (which is a great deal compared to $89.00 for a new assembly from Moss). Turned the key and no fuse blown!

I'm guessing it was the tach and not the blinker (since the blinker shouldn't be hot when the car comes on and the switch is off). I saw a guy in another post who recommended grounding the tach directly to the case. I think that may be the next project.

Thanks for the help.
Ryan R.
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Re: Can't stop blowing these %$#@ fuses

Postby Hey Mikey ! » Wed Oct 22, 2008 12:59 pm

Good job Ryan. By the way--the reason I use "Hey Mikey" as my user name is because of the "Life" cereaI commercials of the 70's. I was given the nickname at an early age and it stuck. I was the teenager taking things apart, blowing things up or shorting circuits and creating small fires. So the stigma-"Hey Mikey--he can't fix it--he can't fix anything" stuck. It wasn't until I took a crack at my dad's Spitfire wiring problems that the stigma changed. My college buddies were standing around the little white Spit--giving me heck--I had created a little smoke under the dash. Of course they were the "experts" of car repair--but they could not figure it out themselves. I got the problem solved--(Another PO miswiring !) and turned over the Spit to a beautiful purring motor. My buddies piled in the LBC and asked for a ride--as we pulled out of the driveway they yelled "Hey Mikey--Ya fixed it--Hey Mikey--he can fix anything" ! So everytime I fix a wiring problem it brings back those days.
If you can--get a DVM--a digital volt meter. The Radio shack cheapies will do the trick. If you are not familiar using one--get some help--maybe a local club member--it will save alot of time and frustration.
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Re: Can't stop blowing these %$#@ fuses

Postby 66 Sprite » Wed Oct 22, 2008 7:49 pm

I have a DVM (worth it's weight in gold). The trouble is figuring out where to stick it and taking the time to trouble shoot the whole thing. I figure most of the issues have happened before so I use this site as something of a short cut. If you hadn't chimed in I would have been trying to figure out what I wired incorrectly, rather than looking for issues with the wiring harness itself. Thanks for the help.

P.S. We used to call my brother Hey Mikey, because he wouldn't eat most foods, but he loved life cereal. Unfortunately that nickname never stuck.
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