2004 e350 dual alt operation

[Rickster42]

I have an 04 ambulance with an int battery light on in dash. it has had a myriad of parts - including both alts and a pcm. it does code p0620 - generator 1 control circuit. p0620 always leads to gen1 replace...hehe

- i can monitor gen1 I circuit at pcm. when concern occurs I circuit drops from 9v to 1.5v and upper alt stops charging and bat light comes on.

Lower alt I circuit at pcm always reads 9v except when glow plugs are on cold start (normal)

- I have volt drop tested upper alt case to ground - .01v

- upper alt bat term - to battery pos - 1.2v - trace that to battery isolator(diode type) but tested a diff 04 my amb with no concerns and it had the same drop on isolator.

- if i rev the engine bat light will go out but comes back on at idle.

- the strangest deal is that when bat light is on - if i activate any switch on the doghouse(rear heat/cot lights...ect)

the bat light will instantly go out..wtf?

- i gotta be missing something simple.... any ideas most welcome...

[Bruce Amacker]

I have an 04 ambulance with an int battery light on in dash. it has had a myriad of parts - including both alts and a pcm. it does code p0620 - generator 1 control circuit. p0620 always leads to gen1 replace...hehe

- i can monitor gen1 I circuit at pcm. when concern occurs I circuit drops from 9v to 1.5v and upper alt stops charging and bat light comes on.

 

This is how the alternator (regulator, actually) communicates a problem to the PCM- the alt. pulls the I-line low, which tells the PCM it has a fault. If this I-line is going from 9v to 1.5v, either the alt. is defective or the harness is rubbed through and grounding. We had a DTS member last year with a similar problem- a Gen 2 code when it only was equipped with 1 gen. It turned out to be a rubbed Gen 2 I-line which is still in the harness even though there is no Gen2. He disconnected the Gen2 line at the PCM and fixed the problem.

 

(See this thread from RockBronco,

 

http://www.forddoctorsdts.com/forums/ubbthreads.php?ubb=showflat&Number=7199&Searchpage=1&Main=1027&Words=%22I-line%22&Search=true#Post7199

 

Hey, the fucking search engine worked, but the link won't!)

 

Another anomaly is your no-fault voltage. On F-models the PCED calls for VBAT in a no-fault situation and 0v in a fault situation. I've measured 12.3v KOEO and 13.4V KOER on several F-trucks on both pins 1 and 4, center connector, PCM engine harness with a BOB. I wonder why yours is only 9v without a fault. I'd suggest you check this on another similar E-van if you have one handy, but I have a hard time believing E-vans would be different from F models in this area. Cutting that wire and overlaying the harness seems like a good idea, or maybe de-pinning the PCM connector and checking the voltage at the PCM pin with the wire unhooked.

 

 

Lower alt I circuit at pcm always reads 9v except when glow plugs are on cold start (normal)

- I have volt drop tested upper alt case to ground - .01v

- upper alt bat term - to battery pos - 1.2v - trace that to battery isolator(diode type) but tested a diff 04 my amb with no concerns and it had the same drop on isolator.

- if i rev the engine bat light will go out but comes back on at idle.

- the strangest deal is that when bat light is on - if i activate any switch on the doghouse(rear heat/cot lights...ect)

the bat light will instantly go out..wtf?

- i gotta be missing something simple.... any ideas most welcome...

I'd put the doghouse switch thing lower on the diag list and concentrate on why the Gen1 I-line is going low. Check the harness, overlay a new I-line from the PCM to the Alt, or change the alt again. The fact that your I-line is going from 9v to 1.5v is your glowing problem to correct.

 

Alt listings are really weird for these trucks- don't swap out a known good unit from an identical truck because they can have different alts, even though they are the same year and model. Verify PN by VIN if you put one on.

 

Good Luck!

 

 

[Rickster42]

Another anomaly is your no-fault voltage. On F-models the PCED calls for VBAT in a no-fault situation and 0v in a fault situation. I've measured 12.3v KOEO and 13.4V KOER on several F-trucks on both pins 1 and 4, center connector, PCM engine harness with a BOB. I wonder why yours is only 9v without a fault. I'd suggest you check this on another similar E-van if you have one handy, but I have a hard time believing E-vans would be different from F models in this area. Cutting that wire and overlaying the harness seems like a good idea, or maybe de-pinning the PCM connector and checking the voltage at the PCM pin with the wire unhooked.[/b]

 

- yes i wondered about the 9v also, however I measure 12v at the I line at the alt pin when disconnected at alt koeo or koer.

as soon as I reconnect the upper alt connector koer (when the fault is there - it is drawn down to 1.5v and bat light comes on.This amb has had 3 motorcraft upper alts in a very short time trying to correct for bat light issue. It appears to be a fairly simple upper alt internal problem - but 3 alts? maybe i need to go new alt?

[Bruce Amacker]

I had a policy at my shop that I changed suppliers (sometimes temporarily, sometimes permanently) when I had two defects in a row.

 

Overlay a wire, and change the alt. I recommend new OE in my classes for these units.

 

Good Luck!

 

 

[Jim Warman]

Rick... is this a Crestline, E-One, Demers or????

 

When the concern happens, does it matter what position the battery switch is in? I'm not a fan of those diode battery isolaters a diode has a 1 ohm resistance... this mimics a fully charged battery.

 

What is the load at normal idle presented by the package? Are you measuring the charge amps at the alternator feed? What are the volts you see at the B+ terminal?... at the alternator terminal?.... When the problem happens? when it don't?

 

I feel that T2 and T3 are inappropriate in that they don't account for a circuits ability to cope with a load... I cannot say that this will or wont affect your testing.

 

Gen 2 wont excite until the glow plugs turn off... at the same time, a concern with Gen 2 might affect gen 1... You have tested the batteries? I test them "both ways" with the Micro 490 as well as a high rate discharge test.

 

Last, but not least.... you are the benefactor of everyone that worked on the bus before you.... and we all know where that can go....