Electrical Short?

[A1Avette79]

I istalled an aluminum radiator (Dewitts) last week with dual electric fans. Within a day my Generator light came on and i noticed the "Battery" guage was reading around 12 (usually 14-15). Next day the guage was lower - then car wouldn't start. Got a jump - went to autoparts store and had the Alternator and Battery checked (both are about a year old- battery is an Ultima Red Top). Tester showed Battery low but not "bad" so i had it charged and I put in a new alternator (stock, 63 amps type). Car started with recharged battery but guage still read low with engine running and Generator light was still on.
The fan system draws its power directly from the battery and is active when the ignition switch is in the ACC mode (spliced into the windshield wiper motor feed) and is grounded to the front cross member rail beneath the radiator. There are 15 amp fuses in the lines from the battery to each fan. Fans work properly as far as I can tell.

Could this be caused by a short in the fan electrical system? A bad ground?

 

[jimbil208]

Hello

I can tell you something about how the charging circuit works.
When you turn the key on,the generator light comes on.
This sends a signal to the alternator.
I happens to be pin 10 on the plug that goes into the dash guage circuit board.
It is + or 12 volts. When you start the car you will have around 14 volts.
If that signal(+ or voltage on pin 10) causes the voltage to go immediately to 14 volts.
As you replaced the alternator,I assume it is ok.
Jim

 

[A1Avette79]

Thanks Jim,
I did some digging today and found a fried power wire in the harness leading to the Alt. The Alt must have gone bad and overheated the wire. Replaced it and all runs fine.
Thanks again.

 

[Ghilliesuit]

Love that Dewitts radiator. My girl runs so much cooler now. It was well worth the money, but i didn't get the one with the fans. But lord have mercy, my poor knuckles and fingers were beat up from putting it in. Direct fit my butt, it took some work but its in lol

 

[Hib Halverson]

I'd reconsider your cooling fan wiring.

First, they need to work only when the ign is in "run" not "acc". Generally, you don't want the fans to run with the key in "acc" and the engine off because they'll rapidly discharge the battery when you have the ign in "acc".

Secondly, you didn't specify if you are using relays to turn the fans on but, generally, that's a better idea than having the temp switch controlling then directly.

Third, it is unlikely that the power feed for the wipers is heavy enough wiring to handle the fans. I don't have an FSM for 79, but I'm going to bet the wiper power feed is not fused for 30 amps.

I have dual electric fans on my 71. They only operate when the key is in "run" and they are controlled by a relay. Very reliable system.

 

[geekinavette]

The fan system draws its power directly from the battery ...

Not when the engine is running it absolutely does not. Your alternator/wiring MUST have enough current sourcing/handling ability to drive these fans, and through a relay (or two relays) as Hib mentioned. Any accessory power feed is not going to be sufficient.