knuckless

ok i had no idea what to title this

anyway i just put an electric fan on my 68 mustang. the problem is that its equipped with the standard 60 amp alternator and im afraid that im not getting enough amps through the car. i left my door open thursday when i was working on my exhaust and the battery died and i have had to jump it the 6 times ive started it since then. the electric fan keeps turning on when the engine temp is warm enough so im afraid its taking away from the cars ability to charge the battery properly

what test with my volt meter can i run on the battery to see if the fan is using to many amps for my 60 amp alternator. i forget the proper volts/amps i should be getting from the alternator to the battery so any help would be great

67mustang302

It depends. The batt is around 12v, but when charging you'll typically see like 13-13.5 on a factory system. My Powermaster 140a charges at 14.8. Basically with a voltmeter hooked up and the engine running and revved up a bit, you should be seeing 13+v in the electrical system.

Ammeters are freakin worthless.

stangtjk

I don't know the specs of your fan but I know the electric fan from a Mark VIII draw 30 amps at start up and around 12-14 amps during operation. The 60amp alt is probably just enough to cover the stock equipment, I'd bet you need to upgrade.

andrewmp6

Yeah you need a higher amp alt and maybe a better battery too.

Greg-J

Minor correction, a battery should deliver around 12v (12.2 or better is expected) and an alternator should deliver no less than 14.4. You should see only nominal changes in voltage when at idle or full throttle. Amperage however will vary quite a bit between idle and full throttle if your alternator is not equipped with an integrated regulator. If you're not reading at least 14.4 with your car running, you're alternator isn't doing it's job.


Your battery is likely toast. Running a battery dead is hell on it, even if it's a dry cell / marine battery. That said, your car shouldn't be pulling more than 60 amps even with the electrical fan, but the fan shouldn't be running when the car is off for more than a few minutes. It sounds like a combination of a slightly underpowered alternator (look into getting at least an 80, if not a 120), a battery that's seen better days and an electric fan that is far too sensitive.

nba1341

I had a similar problem with my stock 55amp alt

upgraded to a 100amp alt (FORD 1G style) from summit and it has been perfect since

67mustang302

If you start adding amperage....you look at upwards of 4 for the instrument cluster, 6 for brake lights, 10 for running lights(20 so far) and as much as 36 for a CD type ignition, so that's 56amps(maybe less depending on your stuff). That's already pushing the limits of a stock alternator, you start turning on the heater....you get the idea.

60amps is weak for a car with modern electrical devices.

Starfury

Greg, these older systems don't usually run at 14.4V. Even some of the systems in newer cars don't. Anything above 13V should be ok.

Also, a good charged battery will have at least 12.3V. I test batteries all the time (and used to do 3-15 a day); 12.0V is low.

knuckless

ok so after running alot...and i mean alot of test here are my results

battery read between 11-12 volts when car is off. try to start the car and it cant even crank. as if it was totaly dead

when i jump the car, it starts up just fine and reads no higher then 12 volts no lower then 11, when i give it some gas it read just a bit above 12 volts. i turn the car off and try to start it...again not even a crank of the engine but the battery read 11 volts

cleaned my batter posts and cables and jumped the car again.
idle and headlights on 11.5
idle headlights and fan running 11-11.5
basically it keeps dropping. i wouldnt even dare turn my cd player on

i went through this last month (replaced the battery and voltage regulator. got the alternator tested) and it was reading around 14 volts at idle.

after a minute or two the volts were very slowly dropping. i have a feeling the alternator isnt even charging the battery that much and its just running off the battery power. tmrw morning im going to get the alternator tested again and check all my connections

67mustang302

You need a new alternator, and your battery is low.

Get a larger 1 wire alternator, at least 100a.