Major electrical screwup.

[DanD]

So, say you managed to charge your battery backwards on an 81 Fiat spider with EFI, and you tried to start it.

Assuming the wiring is not fried, What would you need to replace ? I'm assuming you would start with the ECU and the alternator.

Yes, I really did this, and yes, the battery is really fully charged to reverse polarity. I don't screw up much, but when I do, It is FABULOUS. I'm fairly bummed out here, but I need to start moving forward.

[riverdadd]

i have done that too, charged a battery in reverse, with a old sears charger!. moving forward, get a new battery charger that will sense if the wrong polarity is connected. As far as what is damaged, before you assume something is toast, get another battery and see what works or doesn't . you may get super lucky..... I did. ( my stuff was precomputer)

[aj81spider]

+1 on replace the battery and see if the car works. There's not much on an old Fiat that would get damaged by reversing the voltage. Even the ECU may well have diodes to protect against that. I think there's a pretty high liklihood that you only damaged the battery. I certainly wouldn't replace anything until I'd verified that it was bad after replacing the battery.

[spider2081]

I would inspect the wire that connects the starter's battery terminal to the alternator. I'm pretty sure others have posted here that hooking up the charger backward to the battery caused the alternator to short and the wire connecting the alternator output to the starter solenoids battery post overheats and the insulation melts.
Was the battery connected in the car when you charged it?? I had a friend hook up the charger backward to his car and a few of the wires behind the dash melted. Did you see smoke or smell anything abnormal???
I was just talking to someone about how easy it is to connect to the Spider battery reversed polarity. I'm so use to seeing a red Battery cable on the plus terminal. My Spider has a green wire on the on the plus terminal.

[DanD]

Yes, I fried the alternator and the wire. I put in an alternator and wire from a 79 that seemed identical, and the car fired up with a new battery. The ECU seems fine, I had swapped it with another which kept cutting out, so I swapped back, and it is OK.

I have no instruments, no tach, no gas gauge, no temp and no oil light. The fuse was burnt out, so I swapped it, and I got the oil light back on, but the fuse quickly blew. I don't think I burned any wires, but I don't know yet. I am assuming I fried the tach.

[DanD]

Looks like I need a new gas gauge, and that is all. Look for me in parts wanted.

Can anyone tell me if there will be any harm in running a 79 alternator in a fuel injected car ?

[spider2081]

I am thinking most of the alternators used on the 2L Spiders were Bosch and were either 55 amp or 65 amp alternators. I think the 79 was probably a 55 amp and the 81 could have been a 65 amp. Either should work fine unless you have some super sound system or lights you have added.
From the factory Fiat used a #10 wire between the alternator and the starter solenoid. I feel this wire is marginal under certain conditions. When the battery is dead and the car is jump started the alternator will put out maximum current to charge the battery. A larger diameter wire here would be a good idea. Something like a #8 or even a #6 .

[DanD]

The new one looks like a 10. I really scooted by on this one. I bought a new battery, Now I am draining the old one to see if I can get it charged back to correct polarity.

[bobplyler]

Looks like I need a new gas gauge, and that is all. Look for me in parts wanted.

Can anyone tell me if there will be any harm in running a 79 alternator in a fuel injected car ?

Might be the fuel sender instead of the gauge.

[riverdadd]

i have a spare gauge..........in central VA.....pm me

[DanD]

Looks like I need a new gas gauge, and that is all. Look for me in parts wanted.

Can anyone tell me if there will be any harm in running a 79 alternator in a fuel injected car ?

Might be the fuel sender instead of the gauge.

I took the gauge apart, and I blew it. I may also have fried the sender, but I haven't pulled that just yet.

[DanD]

i have a spare gauge..........in central VA.....pm me

PM sent.

[DieselSpider]

Batteries too many times come reverse polarity when new and a polarity sensing charger won't correct them so you need to use an older manual charger that will force the battery to the correct polarity. This is most often the case with batteries where the electrolyte is not put into the batteries before being sent out to the stores. Many just fill them and put them on a polarity sensing charger and if the battery came up reverse polarity it stays that way. This is more common on power sports/motorcycle and lawn equipment batteries and I have had to deal with it on more than one occasion.

I always check polarity when installing a new to me battery now as they say once bitten twice shy and its a good thing I have started checking considering how many times I have found that snake ready to strike.