Is there any way I can test my alternator for malfunction, or needed replacement?

 

Has your battery been excessively drained as of late?

 

Well as of right now my battery has 12.2 volts. (Thats turned off) 630 CA
And honestly I dont think those Cranking amps are enough for a old 86. I could be wrong. I dont know what my battery reads while running because I cant start it. When I try...the engine barely cranks.

 

Has it just recently started doing this? What size engine engine is it? If is is something like a 351W you would probably want 900 cca's. I have a battery with over a thousand because these New Brunswick winters are cold....

 

Its a 302. I live in minnesota so I might get close to a thousand. It did recently start doing this. I just replaced the iac/abv, and while diagnosing that...i tried cranking the engine countless times...

 

Welp. I finally got'r started. With a new iac, and 1000 CA battery. The funny thing is...its still running like its a bad iac/abv, ...low rpm...step on gas, dies when I come to a stop...any one know what it could be?

 

Take your voltmeter and hook it to the battery with it off. Should be about 12.4 volts, give or take a couple tenths. Start the engine and rev it. Then check the voltage. Should be around 13.6. If it does, then the alternator should be OK. As far as your running problem I would look at the TPS or fuel pressure and regulator.

 

Also, it may be your starter is going bad and not your battery. Starters build up resistance over time and slowly require more amps to kick them over.

 

Thanks guys, ill post more when i get more

 

You can also run your truck and then remove the battery cable, if it stays running your alt is working. But like jeep said it should read around 12 -12.5 off and 13 to 14 with it running.

 

You should never do that, it can cause huge voltage spikes and fry your computer. You could do that to the old generator systems but not an alternator.

 

I agree, DO NOT EVER remove the battery cables while the engine is running!!! The Di/Dt will create huge voltage spikes!!!! The old generator systems didn't have all of the sensitive electronics stuff either!!!

 

Haven't had a problem yet doing that. And the old gerertors would not work that way. They had to have electricity to generate it so it wasn't till the alternators came out that you could run without a battery.

 

Alternators are still generators - they need 12v to generate the moving electrical field that induces current in the stator coils. And removing a battery cable when the engine is running can generate a huge voltage spike in an internally regulated system. It's even worse if the battery is partially discharged - the alternator is already working overtime, and suddenly all that energy has nowhere to go. We're not busting your chops here, but there are much more reliable and accurate ways to test an alternator. A 15 dollar analog voltmeter should be in every Bronco owner's toolbox!

To answer Muddweiser, I would have the battery charged and tested out of the vehicle, by someone with a resistance or "load" tester. If the voltage readings don't register 13-14v with a freshly charged battery and the vehicle running, then remove the alternator and have it bench tested. Always make sure a new alternator has a freshly charged battery to work with. If you have access, the alternator can be "full fielded" while on the vehicle, and this will rule out a faulty voltage regulator. Honestly though, a bench test at Napa or Autozone will give you more useful information.

 

I agree with that. The best way is to take it off and have it bench tested. Some are eve able to put loads on. I was just stateing that you could test them that way, I should have noted though that it is NOT advisable on newer vehicles with the computer controls. My oops.

And yes I know your not trying to bust my chops and niether am I but I disagree with the statement that alternators are still generators, there is a big differance.