Cannot Turn Off Field Output

[stiertj]

My NEXT-12P (#N12892), purchased in March 2007, displays the error indicator code for "Cannot Turn Off Field Output" (CTOFO). The battery banks receive over 16 volts from the Ample alternator (#4023/S, #RR1924). The CTOFO error indicator is displayed even when the engine is NOT running, but the ignition switch is "on". The NEXT step troubleshooting revealed two exceptions: 1.) With the engine running, the house battery receives the excessive voltage noted above, and 2.) In all three test conditions (ignition "off", ignition "on", and engine running), the field tab voltage is 9 volts or more.

There is a jumper between the positive and ground terminals on the alternator, with a 20-amp "slo-blo" fuse and a diode (#MR2535L, #W0032). The diode is separated, resulting in NO connection.

Finally, when a battery bank is "on", the ignition warning buzzer can be heard faintly (at significantly less volume than when the ignition switch is in the "middle" position), even when the ignition switch is "off".

Questions:

1. Is the diode condition a probable cause of the primary error condition? If so, what is the appropriate replacement part, and how can it be obtained?

2. Is the ignition warning buzzer condition related to the primary error condition?

3. What other tests and/or causes of the primary condition should be performed / explored?

Any responses will be greatly appreciated.

/s/ Timothy J. Stier - Cape Coral, FL

[Coulomb]

The troubleshooting guide locate at
http://www.amplepower.com/trouble/index.html will probably answer most
of your questions.

The component on the back of the alternator is a snubber that is used to
limit high voltage transients. Someone was creative and added a fuse
where none should be.

The most common source of high voltage transients is opening of the
battery selector switch, either manually, or under high current. See:
http://www.amplepower.com/apps/burnt_sw/index.html.

Lightning strikes are another source of high voltage transients, which
at your location are frequent.

[stiertj]

I sincerely appreciate your response, but perhaps you could be more helpful.

I have already referred to the troubleshooting guide. In my initial post, I reported two exceptions: 1.) With the engine running, the house battery receives over 16 volts; and 2.) In all three test conditions, the field tab received 9 volts or more.

You stated that the alternator jumper has a "snubber", rather than a diode. OK. Is this broken part a probable cause of the primary error condition? Can you tell me what the appropriate replacement part is, and how I can obtain it?

You mentioned referred to a "transient" condition. The excess voltage I'm getting is NOT "transient" - it's constant.

You did not address the ignition warning buzzer condition. Is this related to the primary error condition?

Does the regulator need to be replaced?

Please re-read my initial post. I look forward to hearing from you.

/s/ T.J. Stier

[Coulomb]

Based on the failures of the tests in the Troubleshooting Guide the
regulator is faulty and needs to be replaced or repaired.

You can order a new snubber from Ample Power.

The snubber will not blow on 16 Volts. It can absorb 1500 Joules of
energy and generally the only way to blow a snubber is a lightning
strike, or opening of the alternator circuit when it is charging at
maximum.

I don't know how your ignition/buzzer is wired, but maybe it has a high
voltage alarm on it.

[stiertj]

Thank you. Now we're getting somewhere.

About the snubber. What is its purpose? Please note that it has NOT blown. As stated in the initial posting, it has been separated, resulting in no connection on that jumper. How would I go about ordering this part?

About the regulator. If it is now inoperable after only 2 years, will the Company provide me with a replacement? I have no warranty information on this, but I do have the invoice.

/s/ T.J. Stier

[Coulomb]

A snubber often separates when hit by a high voltage transient. Do you have a battery selector switch?

Snubbers can be ordered under regulator accessories at http://store.amplepower.com

[stiertj]

Thanks. So what is the function of the snubber?

Yes, I do have a battery selector switch. It appears to be operating properly.

What about the warranty on the regulator?

/s/ T. J. Stier

[Coulomb]

The function of the snubber is to sacrifice itself to save the alternator and hopefully the regulator. It was only partially successful.

Did you read this URL:
http://www.amplepower.com/apps/burnt_sw/index.html. That brand new switch cost the owner about $3500 in blown up electronic gear.

Products are covered by warranty when they are wired according to the wiring diagram. The wiring diagrams show the alternator wired directly to the distribution point and there to the batteries, so there is no switch in the circuit to be opened up and blow things up. It's been that way since 1994.

Ordinarily we give people a trade-in allowance on products , but will only do so in this case on your assurance that you will wire the replacement according to the wiring diagram.

[stiertj]

OK, I have little choice. I'd like to order the regulator and snubber. How do I go about this?

/s/ Tim

[Coulomb]

You need to order the NS2 or SARV3 regulator here:
http://store.amplepower.com/page3.html

The snubber can be ordered here:
http://store.amplepower.com/page4.html

If you return the old regulator, we'll give you a $50.00 credit when we receive it.

See shipping instructions here:
http://store.amplepower.com/page4.html