Dead Battery

The past couple of days I have had a difficult time starting the car on

a cold morning. It seems to crank ok but won't fire. Got the car

started and drove to work. Left work no problem starting car as it was

warmer outside albeit really wet. Big storm came this way. Went to

store, no problem starting car on way home. Got home, dead battery.

The battery is an Optima about four months old. We have replaced

all of the starting/charging system except the alternator. Is there any

way to test an alternator? While running we get 13.6 volts at the

battery but that does not mean it is being charged properly, correct?

Anyway, new alternator on the way from Summit Racing.

http://www.summitracing.com/parts/TFF-7078NA

mike

13.6 volts is a little low and can be caused by either a weak alternator or a battery with a shorted cell. My next step would be to check the load the alternator is capable of. You'll need an ammeter for that. An amprobe clip-on type is the easiest to use. With the engine running turn on the headlights and heater and see if the alternator is producing enough current (amps) to keep up with the load. With a dead battery and the additional load the alternator should put out at least 75% of its rated capacity at 1,500 to 2,000 RPM.

Most of your chain auto parts stores will load check your alternator for free. No obligation.

13.6 volts is a little low and can be caused by either a weak alternator or a battery with a shorted cell. My next step would be to check the load the alternator is capable of. You'll need an ammeter for that. An amprobe clip-on type is the easiest to use. With the engine running turn on the headlights and heater and see if the alternator is producing enough current (amps) to keep up with the load. With a dead battery and the additional load the alternator should put out at least 75% of its rated capacity at 1,500 to 2,000 RPM.

Click to expand...

Thanks for the advice.

Can you point me in the direction of an amprobe clip-on. Sounds

like another cool gadget for my toolbox.

mike

In the past I have used "full field" testing to troubleshoot charging problems. Here is a good link for this test and other test to help you troubleshoot this type of problem. Take a look at the load test, no load test, and full field test. Hope this helps.

http://www.fordification.com/tech/charging.htm

Thanks for the advice.

Can you point me in the direction of an amprobe clip-on. Sounds

like another cool gadget for my toolbox.

mike

Click to expand...

Here's three that do both AC and DC, most just do AC (even the Amprobe brand):

http://www.amazon.com/Auto-ranging-Digital-Clamp-Meter/dp/B001VGND88/ref=sr_1_18?s=automotive&ie=UTF8&qid=1423335784&sr=1-18&keywords=ammeter#productDetails

http://www.oreillyauto.com/site/c/detail/OTC0/3908/N1001.oap?ck=Search_N1001_-1_3490&pt=N1001&ppt=C0103

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

Here's another very handy item, a clip-on inductive ammeter, that everyone used to sell. I looked on line and couldn't find one like it. I've had mine for 30 or 40 years, I guess the digital stuff has superseded them. This one has two measurements 600-0-600 amps for starters and 75-0-75 amps for alternators.



Sorry about the picture quality, my cell phone doesn't do well on close-ups.

Here's three that do both AC and DC, most just do AC (even the Amprobe brand):

http://www.amazon.com/Auto-ranging-Digital-Clamp-Meter/dp/B001VGND88/ref=sr_1_18?s=automotive&ie=UTF8&qid=1423335784&sr=1-18&keywords=ammeter#productDetails

http://www.oreillyauto.com/site/c/detail/OTC0/3908/N1001.oap?ck=Search_N1001_-1_3490&pt=N1001&ppt=C0103

http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

Here's another very handy item, a clip-on inductive ammeter, that everyone used to sell. I looked on line and couldn't find one like it. I've had mine for 30 or 40 years, I guess the digital stuff has superseded them. This one has two measurements 600-0-600 amps for starters and 75-0-75 amps for alternators.

Sorry about the picture quality, my cell phone doesn't do well on close-ups.

Click to expand...

Just bought a Fluke 325 as I have two other Fluke products.

A multi-meter and a visual IR thermometer. We replaced the

entire starting/charging system and it may have been the

alternator all along. There is one arriving from Summit Racing

today so we will go slap it on the car. Thanks for your advice.

mike

Sounds good, Fluke makes very high quality test instruments.

Go old school to check the alternator. With the car running, pull the negative terminal off the battery. If it stays running the alternator is working, if the motor stalls the alternator isn't making enough juice. Not very high tech but it works.

Go old school to check the alternator. With the car running, pull the negative terminal off the battery. If it stays running the alternator is working, if the motor stalls the alternator isn't making enough juice. Not very high tech but it works.

Click to expand...

DO NOT DO THIS! You can damage the alternator diode pack. Don't believe me? Check out this earlier link:

http://www.fordification.com/tech/charging.htm

We replaced the alternator with one from Summit Racing.

Never heard of "Tuff Stuff" as a brand name but they did

not want the core returned. Will do a load test on the old

alternator, maybe nothing wrong with it.

mike

Just checked voltage with my Fluke, 12.46 off and 14.42 running so I think we fixed it.

Thanks for all the advice.

mike