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620 electrical problem!! help!!


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So yesturday as I got home my truck started smoking (73 ..620).. I opened the hood n my throttle cable was red hot n the plastics were burning...the only thing I have changed or done to the truck electronically is changed the battery...fixed my BMW headlights.. n wen I did that it blew the 15 amp fuse so I put in a 25 amp but that was weeks ago.. I fixed the right side speaker on my door..n that's it.. upon further inspection I noticed my alternator (wut i believe is the) ground cable is also burnt up n follows up to right in between the radiator n battery where it grounds.. I haven't seen anything else destroyed as of now but do u guys know wut might be the problem n why?.. I figure it's grounding somewhere but maybe u guys know something else..thank u

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Most likely, the ground between the engine and cab sheet metal went away.  Another possibility, how did you ground the BMW headlights you put in?  Did you just ground them to cab sheet metal?


The negative battery cable connects to the cylinder head by the fuel pump.  From the head ground connection, a pigtail goes down to the alternator frame, to ground it.  There is a second ground wire from the alternator frame to a bolt that holds the voltage regulator to the inner fender.  All these ground wires must be in good condition, make good connections, and if you upgrade the alternator, you should upgrade these wires also.


Did the BMW headlights work for a while with a 15 amp fuse?  If they now require a 25 amp fuse, why the change?  Is one or more of the positive wires for the headlights shorted to cab sheet metal?  If that is the case, and the cab to engine ground was weak to begin with, that would cause the headlight wiring short circuit to find any way it can to get back to the battery, and one way for that to happen is the throttle cable.

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Ok I'll change the wires and check the grounds.. but i'ma have to order a new throttle cable since mine is shot... n Daniel I did not ground the wires to the BMW lights... I dnt even know if they are grounded cuz the truck came with them.. n yes the 15 amp fuse worked for a couple weeks n then pop.. went out..i'ma have to get in der n really check it out though.. just have no time..

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Just make sure you have a 10 gauge (I think will do) wire running from the battery ground to the body sheet metal. This could also be from the head or block to the firewall. Has to be bare metal connections. Just remember that the engine is solidly grounded by the battery cable and the engine/transmission/rear end/ springs and shocks are rubber mounted and insulated from the frame and then there's the rubber body to frame mounts.


There should be a slightly smaller Black wire on the negative battery clamp that connects to the voltage regulator hold down bolt. What happens is the battery cable gets old and replaced with some generic one from NAPA and it doesn't have the wire.You'll have to make your own.

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