Alternator performance

Tony Radford · #1 (**permalink**) 02-24-2009, 04:33 AM

I've got a GM one-wire alternator with internal regulator on my car. What's the best way to tell if it's performing? Batteries only last me a year or so and I'm constantly having to put a trickle charger on it to keep it up. I'm guessing i'm needing a change.

RICK LAKE · #2 (**permalink**) 02-24-2009, 05:30 AM

Tony Radford Tony Couple of questions about your system. Does your car run under drive crank pulley? What power componets are in the car? FI, Radio, how many coolant fans, MSD ignition, Blower motor for heater, head lights, electric fuel pump? All these have drains on the charging system. Heaviest loads are at idle with these systems running. Get a cheap volt meter and check the charging system at idle and at 2,000 rpms. Both should be within 1 volt of each other. If not, you could have a charging issue. With all the power things on in the car at idle you want to see about 12.8-13.2 volts at the battery. Anything less and the battery is not getting a good charge. At idle with the normal power units on, ( ECU,ignition,coolant fan, fuel pump ) you are using about 20-50 amps at idle. Take the ALT to a pepboys or Autozone for an ALT test. This should test the diodes, bridges, and total output of th Alt. Tony send me a private e-mail with number and good time to call you about this, too much to type. What gauge are you running for the charging system? Volt or Ampage? Lets go through the basics before we start looking for problems Rick L.

trularin · #3 (**permalink**) 02-24-2009, 06:14 AM

Tony, I am sure someone will not like this suggestion:

With the car idling, pull the positive battery connection. If the car still runs and you can read a 12 or more volts output from the electrical system, there is a good chance the system is working.

A normal GM system with a single "self excite" alternator will allow a battery to run it's life of 5 or more years. We have gotten up to 7 years on batteries here in the winter wonder land.

1 year doesn't sound right. Rick has a list there that may help you get to the bottom of your problem.

Hope this helps. Like I said, someone will most likely say something about pulling the positive connection to the battery, but it works.

Tony Radford · #4 (**permalink**) 02-24-2009, 09:24 AM

Thanks guys. The car's DC load hasn't changed in years and yet the battery performance is certainly degraded. I do have quite a load between the pusher fans, SPAL puller and audio power amp. I was noticing that I could purchase another chrome alternator with the same case that outputs max power even at idle for $130. If I don't put the charger on it, I won't have sufficient starting current within a couple of weeks of being parked. Every year or so, she'll stop taking a charge and NTB will replace the battery (plus proration). It did'n't use to be that way back when I got the car in 2002.

jwd · #5 (**permalink**) 02-24-2009, 11:25 AM

When you take the idle volt readings, remember that a 1 wire alt. is self exciting and you have to rev it to approx. 1500 RPM to get it to start charging. Personally, I think 1 wire alternators are junk. A 3 wire (still has an internal regulator) has a remote voltage sensing wire and is far superior and I know several that have changed to one because of the problems you are having. Here's a great site that will explain it. http://www.madelectrical.com/electri...hreewire.shtml

Jim

PANAVIA · #6 (**permalink**) 02-24-2009, 02:25 PM

I am a fan of the ford 3rd gen alts, they are basically 2 wire systems, I will post a writeup.

However to see if you are on the good side of the positive, here is my test.

Setup: engine warm at idle, 700RPM all electrical accessories ON ; headlights, fans, heater motor, stereo , foglamps.

---then disconnect the ground wire from the battery,

1. the headlights should not dim
2. engine should not change speed
3. you should get 12.79+V from the positive terminal of the solenoid and a good ground.

--Ideally I like to see 13.79+ in that condition, or by 1400 RPM.

if voltage us under 12.4V at idle, you are playing "Apollo 13" with amps and should upgrade the Alt/system.

--Steve

Yetiman · #7 (**permalink**) 02-24-2009, 04:12 PM

Quote:

Originally Posted by Tony Radford

If I don't put the charger on it, I won't have sufficient starting current within a couple of weeks of being parked.

Is the problem after the car has been left a while ? It sounds like your issue is a current draw when the car is parked, not a faulty alternator.