[CrazyIvan]

So, I've got my 351C in my 72' Mach 1 Mustang.

The baterry has been draining lately. I don't know if the alternator is bad or if the baterry is bad. I've never tested either myself, so I don't know how to do it.

I did put a new rebuilt alternator in about 3 years ago. The baterry is about 4 years old.

I've checked other stuff, like the belt-tightness, fuses, etc..and have come down to either it being the baterry or alternator.

I have a variable AC/DC voltimeter/Ampimeter.

How do I test to see if the alternator is outputting a charge?

Thanks.

[just_a_car]

First off, we have the same year, make, model and engine (though, mine's a 2v, they came in 2v and 4v and you didn't specify). That's just sweeeeet.

For voltage, check this out: Alternator Testing
The first four pages are good for general diagnostics.

The measured amperage with the key off should be 50milliamps or less. The directions are on this site under Parasitic Electrical Drain on Your Battery: saab battery and alternator by swedish wrench

As a side-note, unless you have A/C or a lot of electrical options (such as power windows, rear-window defrost, etc) the original alternator will be 55amp. The A/C model was 65amp.

Here's a good general electrical system testing site with diagrams: http://assets.fluke.com/appnotes/aut...e/beatbook.pdf


Now, if all that checks out, you could have a faulty Voltage Regulator, located on the passenger side of the engine bay with either "Autolite" or "Motorcraft" in silver, white, or yellow lettering. I had to replace mine as it had gone bad. I'll attach a picture of the new one for ya (ignore the bungee cord that's holding the battery down *chuckle*).

*stretches out as he lives up to his username*

[CrazyIvan]

Thanks JaC.

That is cool. I have seen your avatar everytime I look on here and always wondered if it was the same as mine.

Yea, it's a 4V. It's been rebuilt tho with racing cam, aluminum intake, 700 Edelbroch carb, holly headers and Flowmaster H-pipe.

Thanks for the info, I'll try it out this weekend.

You know, now that I think about it, it very well could be the voltage regulator. I noticed when driving above 50 mph at night, my headlights would flicker. I thought maybe there might be a break somewhere in the wiring, also thought it might be the Voltage Regulator, as some electrical problems happened with my mom's 76 F-150 a few years back...so this could be the problem. I think I'll have my head under the hood this weekend.

[Johnny_Revolver]

Could be a dead cell in the battery. Adjust your multi-meter to volts and stick it on the terminals of the battery with the car running, should read 13 ish volts. Alternately, ( nyuk nyuk ) just slip out to the car with the multimeter and check the volts of the battery with the engine off a few times over an afternoon or day, see if it`s loosing charge.

[Oxford]

As a shade tree mechanic here's how I check for voltage loss.

-Remove both battery clamps and clean with something like baking soda solution till nothing more comes off.

-Wire brush both clamps and terminals thoroughly

-Clean exterior surfaces of battery with same solution. Repeat as needed till it's absolutley clear of acid which might have leaked out of caps, etc.

-Use 12 volt battery charger and give the battery a full charge.

-Use a Volt/Ohm/Meter with the settings on DC 12 Volts or more to determine the battery's voltage.

-Wait at least 2-3 hours and remeasure the battery's voltage. As mentioned above by JR, the voltage should have read close to 12.9 V or 13.0 Volts when fully charged.

Conclusion---If there is a significant drop in voltage the battery is defective and probably has a short in one or more cells. Get rid of it before you're caught with a dead battery the next time you have an emergency trip to the gun shop, or sooner.

[SilverRun]

Well, being the expert mechanic that I am - I would ahh take it down to Auto-zone and let them check the alternator for me on their handy-dandy tester do-hicky. But, that wouldn't be near as much fun. I think they will do it for free in lots of places.

[CrazyIvan]

Quote:       Originally Posted by SilverRun

Well, being the expert mechanic that I am - I would ahh take it down to Auto-zone and let them check the alternator for me on their handy-dandy tester do-hicky. But, that wouldn't be near as much fun. I think they will do it for free in lots of places.

"Give a man a fish...."

[alan c.]

Let's make this easy. Using a volt meter set on D.C. check batterry at rest--no load
12.5 + and again with engine running. Increase rpms -- voltage should go up. 14 v or better shows alternator is charging. If you are charging a battery and one of cells is not cooking (boiling). Then that cell is dead. Replace battery.

[Brother Bob]

The battery is four years old. Even if that's not the problem, it will probably be your next problem. If your lights are flickering, you have an electric problem probably in the voltage regulator or a bad brush on your alternator. Could be a broken wire that is arcing to make connection. If your alternator was bad, your headlights would slowly dim, not flicker, and your battery would be dead and so would your car. I believe you just might have more than one problem. Between the guys above me and my recommendations, I'm sure you'll find the problem. Good luck.

[SilverRun]

Quote:       Originally Posted by CrazyIvan

"Give a man a fish...."

Well, I know how to fish, but nothing about testing alternators.

Seriously, I am not quite as mechanically inept as I made out though. I have actually put an alternator in before.

In my own smart@zz way, I was making the point that a lot of the auto-parts stores will check it for free. Fishing aside, that seems like the easy way out to me.

I am all about the easy way out.

I can fri-up some good fish too!

[billy]

teach a man to fish....
and he sits and drinks beer all day!
and buys a steak on the way home.
thats how i did it.

[Brother Bob]

Quote:       Originally Posted by billy

teach a man to fish.... and he sits and drinks beer all day! and buys a steak on the way home. thats how i did it.

Ya know, ............. now that I'm getting to know you, you do fit your avatar.

[billy]

its nice to know im appreciated around here

[Brother Bob]

Your Ok Biily. I don't care what Ezerln, Troy, and Texas-T say about you.

[billy]

[Rufus Rhastus J]

Those old ford regulators were also known to "stick"....so, if the alternator is charging okay and the battery seems okay (a fully charged battery, if good, should not drop below 9.5-10 volts while turning the starter with the coil wire removed)...figure near 350 amp surge as the starter begins to turn and no more than 200-250 while turning. If the volts remain within suggested ranges, the battery and starter are okay. remove one lead from the battery and check for an arc when touching the post to the cable end. be careful! I would suggest you remove the ground battery cable, from the engine block, if it's easy to reach to avoid an explosion from the gases escaping from the battery if it has been charging. If there is a noticeable arc as you touch the cable to ground, it's a good bet your regulator is sticking or, you have a short somewhere in the wiring. I am a retired mechanic myself and know that the regulator problem was very common problem with fords back then. These suggestions I have given you assume you have basic tools like a voltmeter and amp meter. BE CAREFUL!!!!! Batteries can, and do explode! Another easy, quick way to check to see if the alternator is charging, anything that is steel can be touched to the rear bearing of the alternator while the engine is running assuming you can do this safely. A screw driver blade works well to keep your hands clear of moving belts, electical connections on the alternator and such. If the blade is attracted magnetically, you got charging going on. This method assures the alternator is working but, doesn't answer the question of how much charging is taking place. Oh, and one more thing.....BE CAREFUL!

[CrazyIvan]

RR,

Thanks. I've done a lot of work under that hood...but checking for a working Alternator was not something I have done before. I bought a new voltage regulator, it probably needs it anyway, I think the original one is still in there. LOL. Then I'll move on from there.

I've checked the baterry, it never dropped below like 10.5 volts, even when the car wouldn't start. But, hook up some jumper cables or my baterry charger, and off to the races.

Can the voltage regulator effect the distributor? If so, that also answers a TON of questions...

[Rufus Rhastus J]

Quote:       Originally Posted by CrazyIvan

RR, Thanks. I've done a lot of work under that hood...but checking for a working Alternator was not something I have done before. I bought a new voltage regulator, it probably needs it anyway, I think the original one is still in there. LOL. Then I'll move on from there. I've checked the baterry, it never dropped below like 10.5 volts, even when the car wouldn't start. But, hook up some jumper cables or my baterry charger, and off to the races. Can the voltage regulator effect the distributor? If so, that also answers a TON of questions...

Does your car still have points? I'm thinking you got electronic ignition on that car. However, it requires electricity to operate the coil. If volts are low, then the spark will suffer. If you have electronic ignition, remember the "trigger" that causes the ignition coil to fire is accomplished by magnetic fields supplied by the reluctor which is the part in the very center of the distributor (it sorta looks like a spider with eight legs) below the rotor. These magnetic fields swing past the pick up coil located near the reluctor(horizontally mounted on the advance plate where the points, if you had them, would be mounted). The pick up coil is just a coil of wire wrapped around an iron core. As the magnetic fields rotate past this little coil, while turning the engine to start or, while the engine is running, small electrical charges are generated. This is what "triggers" your control module and orders the coil to spark. If you have points, they serve the same function as the reluctor and pick up coil. however, if system voltage is low, this low voltage condition can cause excessive metal transfer and prematurely ruin the point set. Excessive voltage can cause arcing and do the same damage. REMEMBER the basic rue of electricity: When volts go up, amps go down....and, it follows: when volts go down, amps go up! This is why, when the battery is low, you might read as much as a 400 amp draw on the battery when the starter is engaged. but, it reads only 8.0 volts, or less, as the starter begins to turn. This is why low voltage can damage points and other electrical parts like the starter or alternator. Remember, the alternator may be rated at 60 amps.....but, that's not for continuous operation or long cycles as might be experienced with a chronically low charged battery! If you have an amp gauge on the dash, you may notice, when you start the car, the amp gauge shows a pronounced charging rate which tapers off to very little after the engine has been running a while. That's because the alternator is recharging the battery with the electricity that was consumed to start the engine. If the battery is near total discharge, the alternator then is tasked with total recharge which, in worst possible scenarios, could call for maximum output to fill the battery's order for replacement electrical charge. In this case....POOF! the alternator burns out due to overload or over heat. I hope my little primer has helped you understand how things get "fired up!"

[SPOCAHP ANAR]

An easier way would be to go to Advance, Autozone or O'Reilly's and have them test it for you for FREE. They can check the alternator and the battery I believe.

Then pick up the part and fix it, on the spot if ya feel like it.

[Rufus Rhastus J]

and where's the fun in that? Ain't be learn nothin' either.