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Topic: Engine start battery voltage drop. Where to get fixed in Tucson AZ? (solved) (Read 1305 times) previous topic - next topic

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #25 –
Quote from: wolfe10 –
Yes, assuming the "sense wire" is connected (it is a small wire and can break) is OK, then indeed, the alternator is the likely culprit if not voltage at B+ of alternator/center lug of isolator (as they are connected by a single large gauge wire).
Joe/Brett,
For a three wire (B+, Ground and remote sense wire) alternator configuration, if the sense wire is disconnected or broken, the alternator would believe that its output is low (0 Vdc) and the B+ alternator terminal would read somewhere from 16 to 17 Vdc (whatever the maximum output would be that the alternator's internal voltage regulator would allow). So, with the ground wire good (and verified 0.0 ohms resistance), the engine running at 1000 RPM and the sense terminal reading 12.XX Vdc (essentially engine start Battery (+) voltage), if the alternator's output terminal is 0 Vdc, the alternator or its internal voltage regulator is broken.  However, as JD and others have noted, the alternator output terminal and the alternator output cable are two different items so make sure the terminal and cable are reading the same.  From experience (Thanks Escondido), the alternator B+ output terminal can be 14.7 Vdc and the cable can be near 0 Vdc, due to an oxidized, corroded or just plain poor mechanical connection on the alternator B+ terminal.  Same thing applies to the B+ terminal (center terminal) on the isolator (although less likely due to less vibration and corrosion susceptibility, if it is mounted up on the firewall).
Neal
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Neal (& Brenda) Pillsbury
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Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #26 –
Quote from: Neal Pillsbury –
For a three wire (B+, Ground and remote sense wire) alternator configuration, if the sense wire is disconnected or broken, the alternator would believe that its output is low (0 Vdc) and the B+ alternator terminal would read somewhere from 16 to 17 Vdc (whatever the maximum output would be that the alternator's internal voltage regulator would allow).
Neal:
This may be true for a Leece Neville alternator. I have a 300 amp Delco 40SI alternator installed with sense wire. Delco documentation states the 40SI & 55SI alternators will function without the sense connection (regulate B+ voltage at the B+ terminal instead). I have tested this to see what would happen if my sense wire broke - I could still drive, but with slightly lower voltage at the batteries (due to isolator diode voltage drop) until I could repair it.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #27 –
Thanks for all the input.  I will measure the voltage at the alternator B+ terminal and if it's zero, will repair/replace the alternator.

PRFleming brought up a good point.  I don't know if this is the original alternator.  I haven't been able to find info about what was originally installed, just a brochure on the basic model that list 21 different possible models.  How do I find out what alternator was originally installed?

Also, I notice many of you post your "build" number in your signature.  Where is the build number located?  Is it the last four of the VIN?

Thanks - Joe
2008 Nimbus

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #28 –
Joe
The build number is the 4th - 7th digits of the Foretravel coach model specification on your chassis plate.

A quick call to Foretravel, they can give you the original alternator info.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #29 –
Do not know if this applies in your case but the build # was placed under the lift up dash in front of steering wheel as well.
JohnH
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Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #30 –
It was the alternator.  I removed it on Monday and dropped it off in the afternoon at:

Tucson Alternator Exchange
1401 E. 20th St.
Tucson, AZ  85719
520-622-7395
Tucsonalternator.com

They are related to Copperstate Alternator Exchange in Phoenix that Forewheelers (Lynn and Marilyn) recommended.  There were lots of good reviews about them on the web.

When they rolled it around on the counter to find a part number, chunks of metal fell out of it.
On Tuesday they quoted $383.00 + tax = $402.85 to replace the following:
Capacitor, bearings, brushes, brush holder, regulator, rotor, and a gasket.
I picked it up on Wednesday afternoon and installed it today.  After starting the engine, when the "Silverleaf" gauge came to life, it showed charging at 13.7 volts and rose to 13.9.

I'm very pleased with TAE and would recommend them without hesitation.

According to MOT, the original alternator was a Leece-Neville 4884J 200 amp.  The current one is a Leece-Neville 4874JB.  TAE told me it was 270 amp, but the receipt only shows the part number.

Thank you everyone for guiding me through the diagnosis process.

Joe
2008 Nimbus

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ? (solved)

Reply #31 –
Joe,
If your alternator has a larger output than the original one you should check the rated capacity of your isolater to confirm that it can handle the output of that alternator.
JD

John Duld
1995 U320C SE 40'
 

Re: Engine start battery voltage drop. Where to get fixed in Tucson AZ?

Reply #32 –
Quote from: joe g –
It was the alternator.  I removed it on Monday and dropped it off in the afternoon at:

Tucson Alternator Exchange
1401 E. 20th St.
Tucson, AZ  85719
520-622-7395
Tucsonalternator.com

They are related to Copperstate Alternator Exchange in Phoenix that Forewheelers (Lynn and Marilyn) recommended.  There were lots of good reviews about them on the web.

When they rolled it around on the counter to find a part number, chunks of metal fell out of it.
On Tuesday they quoted $383.00 + tax = $402.85 to replace the following:
Capacitor, bearings, brushes, brush holder, regulator, rotor, and a gasket.
I picked it up on Wednesday afternoon and installed it today.  After starting the engine, when the "Silverleaf" gauge came to life, it showed charging at 13.7 volts and rose to 13.9.

I'm very pleased with TAE and would recommend them without hesitation.

According to MOT, the original alternator was a Leece-Neville 4884J 200 amp.  The current one is a Leece-Neville 4874JB.  TAE told me it was 270 amp, but the receipt only shows the part number.

Thank you everyone for guiding me through the diagnosis process.

Joe
do a google search for leece Neville 4884jb it is still a 200 amp alternator
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