throwing codes

93 auto air, getting this code,41 Alternator field switch. Switch not operating correctly and check charging system is the alternator pooched or is it something else. New optima like battery. Is there something else I should check or swap in my alternate alternator? T

anyone

"Alternator field switch?" Without looking that up and just guessing (which I really hate doing, by the by...) I'd say it almost sounds like it could be an "open" in the field coils. Fortunately, the regulator circuit in the PCM going out is quite rare.

Have you checked voltage at the battery, engine running vice not? Could be an important clew...

Thanks for the reply 5-90, I was going to pm you on this if no one replied. What happens is sometimes, usually when I get in to come home from work rather than when I get in to go to work in the morning, the check engine light will come on, I've had this occasionally for a month or 2, but recently the voltmeter will read almost in the red at start up, sometime it will correct itself when I rev it up but lately its been taking a minute or 2 on the road before it will "kick" in, while its in the red of course the lights are dim etc. so I know I have a voltage issue, thought it was just the alternator though, it is getting older now, at least the 3 years that I've had it. Any ideas anyone?
By the way this never happens when we're rolling, once I'm going the check engine light never comes on, just on start up.

tkjeeper said:

Thanks for the reply 5-90, I was going to pm you on this if no one replied. What happens is sometimes, usually when I get in to come home from work rather than when I get in to go to work in the morning, the check engine light will come on, I've had this occasionally for a month or 2, but recently the voltmeter will read almost in the red at start up, sometime it will correct itself when I rev it up but lately its been taking a minute or 2 on the road before it will "kick" in, while its in the red of course the lights are dim etc. so I know I have a voltage issue, thought it was just the alternator though, it is getting older now, at least the 3 years that I've had it. Any ideas anyone?
By the way this never happens when we're rolling, once I'm going the check engine light never comes on, just on start up.

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The voltmeter in the IP is usually lying to you - back-check it with a decent DMM directly at the battery terminals!

Nominal battery voltage (engine OFF) is 12.0-12.6VDC
Nominal charging voltage (engine running) is 13.2-14.0VDC.

If the alternator's output is getting flaky, it can present as a "regulator fault" - and the PCM will throw a regulator code about 1/3 of the time (I've seen it before with ChryCo stuff.)

5-90 said:

The voltmeter in the IP is usually lying to you - back-check it with a decent DMM directly at the battery terminals!

Nominal battery voltage (engine OFF) is 12.0-12.6VDC
Nominal charging voltage (engine running) is 13.2-14.0VDC.

If the alternator's output is getting flaky, it can present as a "regulator fault" - and the PCM will throw a regulator code about 1/3 of the time (I've seen it before with ChryCo stuff.)

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My ip meter has in the past been relatively accurate, I can watch it fluctuate when I engage the fan etc. but I dont trust it entirely obviously. I do have a decent dmm and I will do that check tomorrow. The next time I get it to act up with the low voltage(as I can see by the dimmed cluster lights etc.) I will check it running at the battery. So if I have a low reading when the engine running what else could it be but the alternator, or do I want to know. Thanks 5-90, I appreciate your help, by the way while I have you can you tell me if my new alternator from my recently retired 87 aw4 w/air and auto will fit into my 93 ho auto w/air aw4. Thanks again.

It means somethings wrong at the alternator. Could be slipping belt, bad connection on the alternator, etc. Dim lights are a sure clue that somethings wrong. I believe the PCM controls the ground side of the field coil. Don't the Renix and HO alternators mount in different spots?

tkjeeper said:

My ip meter has in the past been relatively accurate, I can watch it fluctuate when I engage the fan etc. but I dont trust it entirely obviously. I do have a decent dmm and I will do that check tomorrow. The next time I get it to act up with the low voltage(as I can see by the dimmed cluster lights etc.) I will check it running at the battery. So if I have a low reading when the engine running what else could it be but the alternator, or do I want to know. Thanks 5-90, I appreciate your help, by the way while I have you can you tell me if my new alternator from my recently retired 87 aw4 w/air and auto will fit into my 93 ho auto w/air aw4. Thanks again.

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Not directly. The alternator from your 87 is a Delco CS-130 with internal regulator, and the unit in your 1993 is a Nippondenso with external regulator (regulator in the PCM.)

Physically, you can probably make the thing fit with some work. Electrically, expect to get a "persistent MIL" - since the regulator in the PCM doesn't have to do anything anymore, the PCM will end up thinking it has failed, and will throw codes at you. You won't be able to make them go away, either...

(Oh - the "fairly accurate" comment isn't entirely unexpected. My RENIX meters are "fairly accurate," but they're only really useful as indicators for relative state of charge, not absolute voltage. This is why there are grease pencil marks on the IP window - so I can tell when the voltage is actually nominal. You should see gage action with voltage changes - but that's still not a reliable indicator of actual voltage, in this case. That's why the very first thing you should do when you see something goophy is to confirm what you're seeing by digging out your DMM...)

ok, I'll check next time it happens, I'll keep u posted guys, thanks again.

Ok guys, once again today was the same story, started perfect this morn, no code, got in to come home tonight and code, so I checked battery output. Not running 12.17 volts, running this morning 14.74 volts, all ok right? Tonight same not running voltage 12.17, but running was 11.74 volts. This lasted for approx 1 minute when the dash voltmeter kicked back up and lights came on full power and all's ok for the rest of the trip. I just dont want to replace the alternator and still have codes, the alternator is at least 3 yrs old. Thanks