1994 holiday rambler, F-53 chassis, 460 ci engine- Battery was completely dead and while attempting to jump start the cables were reversed (bonehead!). A brief puff of smoke and burnt plastic smell in the engine compartment when ignition was turned on, but nothing else. Thorough flashlight exam of engine compartment failed to find the source of melted plastic smell- battery is intact (thank God..)and still dead. Where do I start to troubleshoot and repair the damage of my boneheaded jumpstart attempt?

scottmarsc wrote:1994 holiday rambler, F-53 chassis, 460 ci engine- Battery was completely dead and while attempting to jump start the cables were reversed (bonehead!). A brief puff of smoke and burnt plastic smell in the engine compartment when ignition was turned on, but nothing else. Thorough flashlight exam of engine compartment failed to find the source of melted plastic smell- battery is intact (thank God..)and still dead. Where do I start to troubleshoot and repair the damage of my boneheaded jumpstart attempt?your lucky the battery was dead that,s why no big damage anyhow charge up the battery and then see what works and what dont and trace from there.

May have burned the main fuseable link. Usually connected to the starter solenoid.

You probably toasted one or more relay coils. They smell lick plastic when they get hot and have a melt down. You may want to install a good battery, get it running and see what isn;t working. Things like headlights, horn, wiper. Good luck.

+1 for a fusable link. BTDT on a car.

Relay coils do not care about battery polarity. Ditto the fusible link. Inspect all wires around battery in case a light weight one melted. You may have multiple blown fuses so take your time sorting things out.

cables reversed during jump start attempt | Good Sam Community

scottmarsc
Explorer
Oct 03, 2013
Update: Had power to the starter relay solenoid from the battery and power from the ignition when key turned to start, but no power to starter- jumping across the large terminals kicked over the engine. Installed a new starter relay solenoid and the engine fired right up, minus output from the alternator. Alternator tested bad, and while installing a new one noticed a hairline crack and small leak from the engine thermostat housing. Of course one of the bolts broke off, thankfully above the block, and with a little tapping from a hammer and heat from a tourch I was able to get it out with a vicegrip. Neither Ford nor NAPA shows a listing for a new thermostat housing, so thanks to Autozone I should be back in business today. Thanks to everyone for your input and suggestions- couldn't have done it without you!
YC_1
Nomad
Oct 01, 2013
allbrandauto wrote:
don't think that's your problem I work on 12 volt electrical system on cars test small wire on sol. with 12 volt test light should lite up when trying to crank if not I am shore you blew a fusable link test again with test light

Ditto:

Not likely the starter relay. No reason it would have failed.
Relays could care less about voltage polarity,.
allbrandauto
Explorer
Sep 30, 2013
don't think that's your problem I work on 12 volt electrical system on cars test small wire on sol. with 12 volt test light should lite up when trying to crank if not I am shore you blew a fusable link test again with test light
scottmarsc
Explorer
Sep 30, 2013
Thanks for all your input- installed a new battery today, traced power to the starter relay solenoid. Turning the key caused the fuel pump to start, but not a noise from the engine. Shorted across the two large posts and the engine cranked. Off to NAPA for a new starter relay solenoid tomorrow and see what happens after the engine starts.
Dale_Traveling
Explorer II
Sep 29, 2013
I don't think you harmed anything either. Reversing jumper cables happens many times a day. Suspect the burning smell was the jumper cables over heating. Usually what happens is a battery explores.
NMace
Explorer
Sep 29, 2013
I doubt it harmed anything. Charge the battery and then find out, don't borrow trouble.
RayChez
Explorer
Sep 29, 2013
Just because it sparked when you made the contact does not mean you damaged anything. Charge the battery and then start the engine to see if there is any damage. Maybe you got lucky and nothing happened.
Peg_Leg
Explorer
Sep 29, 2013
Check the alternator's output once you've got it running. Not familiar with Ford's but I've seen GM one's with the diodes burnt out. I've seen the smoke rising from the alternator on a 65 Mustang from just the same reason.
Daveinet
Explorer
Sep 29, 2013
Possibly your battery isolator. But you really are going to have to charge the battery, and start it up and see what doesn't work. We can make a ton of arm chair guesses, but that is all they are - wild guesses. Until you fire it up and see what doesn't work, you have no place to look.
Jagtech
Explorer
Sep 29, 2013
If it didn't burn the fuseable link, then the smell may have come from your alternator. Is the charging system working now?
Most engine management computers are reverse-polarity protected internally.