my car has a slow drain on the battery, if i put my electric fans on or headlight it kills the battery within an hour....

car is an 86 350 carbed 5 speed, was orginally a 2.8 mpfi. I elimated the computer and wiring right down to the basi engine harness, no probs worked fine.

my car was working perfectly fine, then someone wanted to trade a serpintine setup for my vbelts, so i jumped on that train. i put a new alternator on it, switched my 2 wire alt wires to the one wire (+) and put the other ground wire from the 2 wire plug to the block. i put a new 4 awg wire from battery to alt.

everything worked fine at first, no problems but when i started to drive across canada i noticed my voltage dropped to 12v, then eventually i drove it till i had less than 8v. i had it up to 14v twice for about an hour or 2 each time before i stopped for gas and back down to 12v then dropped

so i have a new battery (optima 6 pack red top), wire to alt, removed my own circuts i put in (toggle switched fans and autometer gauges) and still no luck. i have had the alt checked and it was fine. my grounds seems fine (batt to fender then batt to block and even the firewall to block) i have the same voltage at the alt when the car is running as the battery but it seems to maintain the battery with nothing but the dist running but if i use headlights or turn my fans on itll die very fast. my serpintine setup is off a 93 chevy half ton (yes my hood closes fine just no insulation and had to bend a tab but works fine)

im stumped haha

 

u got a picture of this setup???, sounds like u missed something or wired wrong....

 

It sounds like the alternator is wired wrong.

 

What size pulleys are the serp setup and what was the size of the vbelt stuff? Crank pulley and alternator pulley ratios?

Could have a alternator pulley size that is not turning fast enough to keep charge up when under load. Has happened to me with underdrive swaps where crank pulleys changed diameter but alt pulley stayed same.

Also if you changed alternators are they both the same amp rating? Is it a good alternator?

 

I'd like to agree with this. Were the voltage just low, I could believe it a possible pully issue however, with the varying voltages, I tend not to think of this as a pully problem.

I did the serpentine swap as well on my 84 T/A. If you do a search on the Serpenting swap, ther is a thread that ells you which of the 4 wires coming off the new serpenting alternator you need to tie into your original V-belt alternator harness. It's late now, if I can, after work tomorrow, I'll take a picture of my wiring. Hopefully it'll help.