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Discussion Starter #1
Have a tough one, at least for me...

Have a 01GC 3.3L with 140k miles on it. Replaced alternator/generator with reman one ~2 years ago to deal with squeeling ADP. Have used tie wraps in past to adjust wire harnesses away from heat shields and rubbing into edges of parts. Replaced battery about <3 years ago (terminals are in good shape still). In NorCal so no road salt or rough weather...

About 1 year ago, when starting the car, the speedometer needle would occasionally dance to full speed and settle. Occasionally, would have to reset the cluster if needle got stuck. Read around that alternators may cause this so I thought maybe my reman one is going.

Well, a few weeks ago, I got a P0622 code with the battery light on indicating "Generator Field Not Switching Properly". Not right away, but after driving some.

So while cleaning the battery terminals and when battery was out, had battery checked, and it was bad so received a new one for free due to the warranty (probably dying a slow death due to this before error code coming on). Decided to have the alt tested while all apart, and it was "fine" (was not able to get a free swap-bummer...)

Same error once all hooked back up. Sometimes right away when starting and sometimes not over the last two weeks.

Seems like I hear a slightly larger whine when battery terminals read 15.9VDC and batt light comes on. Also light intensity in car changes slightly. Normally, battery terminals read 12-13VDC when running. When off, get 12 something... Need to double check-this if off the top of my head.

Next, looked at the harnesses and checked continuity with ohmmeter between the alt rotor, the IPM, and the PCM. No visible signs of corrosion or issues. Wire brush roughened contacts on big IPM connectors to be sure have fresh contact. For example, PCM C1pin6 to splice 112/IPM C4pin3(ASR)/AltRotorField1 and PCM C1pin8 to AltRotorField2.

Took out PCM and opened it to see if any signs of damage such as burnt components, but it is filled with a gel so can't see squat... But I needed to see the PN anyway for the next step below: 04727402AI but the dealer upgraded it to AK at some point.


Went ahead and just ordered a reman PCM (will have VIN preprogrammed in) to see if it is related to the voltage regulator or something else.

Heard that that new alts can create havoc in other components due to surges, but not sure if true. Hope that is it the PCM, otherwise, it must be the harness, and that is a big deal to swap out...


Anyone have any ideas on what to check for? Jeepman-need your opinion!

Can anyone send me their battery terminal voltages when engine is off, on, maybe after battery is charged so I can compare? Need to know what to look for now and once new PCM is in.

Thanks, Mike
 

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Quick question. Did that reman alternator have a decoupler pulley or a standard pulley? I hope it has a decoupler pulley or else you are putting some strain on the rest of the accessories.
 

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Discussion Starter #3
Has the correct ADP/decoupler pulley on it. Thanks for asking for clarification!
 

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Discussion Starter #4
After reading up on some other threads where atoman and others posted, I wanted to add that I already changed my starter years ago due to worn out contactors, swapped the ASD relay with another, and that I will

1) start monitoring DC & AC voltage with my DVM using the cig lighter outlet to see if can watch the charging range (according to battery temp sensor section of the manual, the PCM tries to control the battery voltage to 13.5-14.7VDC based on battery temp)
If I see any AC, then have to wonder if the alt is bad after all-maybe a bad diode.....
2) check the alt voltage which is supposed to be 14.0+-0.5V according to the manual
3) go back in with some terminal cleaner/lubricant/antioxidizer on some of the key IPM & PCM pins

I forgot to ask what version (greater than AK?) have people had flashed into their PCM and could it help?

Also, what's the best way to check for good grounding since there are so many grounding paths to the chassis and they should be tied together within components, right?

I think that the batt light is coming on due to overcharging having once seen 15.9VDC on the battery leads so probably the new PCM will solve it unless the alt has something to do with determining that voltage. Does it? Chicken or the egg....
 

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An alt should never go much above 14.5v, 15.9v will fry the batt in short order. Basic voltage control is by the voltage reg inside the alt, the computer is a fine tuner which adjusts for temp. 15.9v could burn out bulbs and is the reason they are so bright. Probably won't harm computers because they surely are surge protected?

So, I agree, the alt is probably bad - not unusual for remans although I always use them and have always had good luck.

A fully charged batt will show around 13v right after being charged by a correctly operating alt. After it sits a couple of hours it will drop to appx 12.65 -.85v. You need a good digital VM to get accurate readings, but these are ballpark.
 

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check the rotor field wiring, if you're getting over 15Vdc it's getting shorted to ground either in the wiring harness, alternator case or PCM (or rotor winding is damaged).

There is NO voltage regulator of any kind in these desno alternators - the field is controlled solely by PCM circuitry.
 

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The thing that makes an alt over charge is too high voltage to the alt field. If the field circuit is shorted ahead of the alt there will be no voltage to the field and no output? If it is shorted at the end of the field circuit the alt will output as high as 40-50v!! Since this one is only making slightly above normal it appears to me it is a VR problem.

My factory maint manual says the alt has an internal VR and the computer only adjusts for temp, is this wrong? I know these vans use different alts but I can only assume the manual is correct. I stand corrected if not.
 

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The thing that makes an alt over charge is too high voltage to the alt field. If the field circuit is shorted ahead of the alt there will be no voltage to the field and no output? If it is shorted at the end of the field circuit the alt will output as high as 40-50v!! Since this one is only making slightly above normal it appears to me it is a VR problem.

My factory maint manual says the alt has an internal VR and the computer only adjusts for temp, is this wrong? I know these vans use different alts but I can only assume the manual is correct. I stand corrected if not.
You must be looking at wrong FSM, the alt is nothing more than two 'Y' configured stator windings with a 12 diode bridge and a connector for the rotor field winding (diesel engines have a single Y on stator and an eight diode bridge)
 

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Discussion Starter #9 (Edited)
PROBLEM FIXED....

Bad remanufactured alternator!

Picked it up a couple of years ago at PB because I couldn't get that dang ADP off the orig Denso alt when I only wanted to get rid of that squeal for the wifey... That's the price I pay...

Looks like I won't need that new PCM after all-luckily the place I ordered has a 14-day money-back guarantee. Wheh...

But this was a pain since when I first suspected the alternator based on a year of the tach needle flipping out and reading 3rd gen forums, I took it to PB and their testing unit said AOK (first thought tach issue was from AT speed sensors but new sensors didn't fix it). So they wouldn't swap it with the lifetime warranty. But did get a brand new battery out of it since still within PB 3year full warranty (Only bright spot to this hole story).

Well, since that test and the new battery, the bat light was intermittent but recently was on all the time and my (brand new) battery was draining...

While waiting for the PCM to be mailed to me, went ahead and bought a new reman alt from PB (since many other 3rd gen posts say the reman alts go bad) and wa-la, the voltages are normal, and the battery light is off. Charging voltages are within range quoted by manual in bat temp sensor section and engine-off voltage showing charged battery again ~13.0VDC. Tach needle not flipping out so far after ~6 starts-keeping fingers crossed...

So word of warning to all, that at the first sign of trouble, suspect and swap the remanufactured alternator/generator probably due to the bad voltage diode bridge. Prove 'em wrong and buy another to see issue goes away if they won't honor the warranty initially, and if issue goes away, then force them to honor it like I did (so no extra $$$)

Thanks Atoman and Gusc!!!

Now, just have to build enough courage to drop the tranny to fix my only remaining oil leak-the dreaded rear crankshaft seal... This summer... Gives me a chance to refurb the tranny too-but won't take a chance on buying a rebuilt one based on this alt experience, reman half-shafts eventually creaking (even bent one), and a reman power-steering pump slightly leaking...

Mike
 

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Glad you found the problem, always a good feeling of accomplishment.

Atoman, I stand corrected. You are absolutely correct. I went back and re-read the manual and it specifically says there is no separate VR (EVR they call it). I must have read the temp compensating part as the only thing the PCM does rather than part of what it does! I remember being surprised at the time that the computer did not act as a VR, but I was in a hurry looking for something else and didn't go back to read it again.
 

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Glad you found the problem and it didn't cost you a fortune!
 

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Discussion Starter #12
Just a quick update...

Still get the occasional speedometer needle spiking to various degrees at startup. So not sure the new reman alt responsible. New AT speed sensors installed last year didn't fix it...
 

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One online rebuilder states that his fixed pulley rebuild is superior to the one with an ADP. Prices are almost the same.

Anyone have any experience with this?
 
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