Low voltage and Check engine Light

Topic: Low voltage and Check engine Light (Read 1772 times) previous topic - next topic

Re: Low voltage and Check engine Light

Reply #25 – November 24, 2023, 04:30:12 pm

The 15A device in your diagram is probably a auto resetting circuit breaker.

Re: Low voltage and Check engine Light

Reply #26 – November 24, 2023, 04:32:00 pm

DUVAC trace (1 is the isolator, 2 is the circuit breaker)& Wilson pic showing IGN and DUVAC

Re: Low voltage and Check engine Light

Reply #27 – November 24, 2023, 04:37:05 pm

Quote from: stevej – November 24, 2023, 04:26:17 pm

Which further supports that the small post wires are reversed, no?

If my theory is correct, yes, having the small wires reversed on the alternator could cause what you observed.

Re: Low voltage and Check engine Light

Reply #28 – November 24, 2023, 04:40:55 pm

Do you think there's a less risky way to switch them (ie, only connect one)?

Re: Low voltage and Check engine Light

Reply #29 – November 24, 2023, 04:42:57 pm

Quote from: stevej – November 24, 2023, 04:40:55 pm

Do you think there's a less risky way to switch them (ie, only connect one)?

I can't think of any other way to test. Both EXCITE and SENSE wires are required in order for the alternator to function properly.

Re: Low voltage and Check engine Light

Reply #30 – November 24, 2023, 04:45:11 pm

The ignition wire is only hot with the key on and the sense wire is hot all the time.

Re: Low voltage and Check engine Light

Reply #31 – November 24, 2023, 04:53:21 pm

Quote from: stevej – November 24, 2023, 04:32:00 pm

DUVAC trace (1 is the isolator, 2 is the circuit breaker)& Wilson pic showing IGN and DUVAC

Your diagram shows two alternators. Does your Nimbus have dual alternators?

Re: Low voltage and Check engine Light

Reply #32 – November 24, 2023, 04:59:55 pm

Just one alt - the diagram shows options (dotted lines) for different models: 160A for Nimbus, 200A/270A for Phenix

Switched the wires and started it up, dash shows 13V, 13.4 at the chassis on isolator, 14.2 on alternator post. Didn't see any magic smoke escape. I think it might be good...

Re: Low voltage and Check engine Light

Reply #33 – November 24, 2023, 05:02:29 pm

Quote from: stevej – November 24, 2023, 04:59:55 pm

Switched the wires and started it up, dash shows 13V, 13.4 at the chassis on isolator, 14.2 on alternator post.

Better - I believe the wiring is now correct. Go have a cold one!

PS: When your batteries are pulled down a bit (discharged) you could see a lot higher voltage on the isolator center post. You might see over 15 volts at times - this is fine. It can take well over 14 volts (at the battery post) to recharge a depleted 12 volt battery bank, and the center post (on a diode isolator) always runs about 0.7 volts higher than the battery posts.

Re: Low voltage and Check engine Light

Reply #34 – November 24, 2023, 05:07:39 pm

Quote from: Chuck & Jeannie – November 24, 2023, 05:02:29 pm

Much better - I believe you solved your problem. Now go have a cold one!

Holy cow - such a small detail - I would never have been able to troubleshoot that on my own. Thanks for your help, hopefully I can pay it forward soon! Beers on me at the next campground!

Re: Low voltage and Check engine Light

Reply #35 – March 30, 2024, 05:11:57 pm

The Winter 2024 issue of MotorCader included an article in the Service News discussing the issue of intermittent low voltage. The author, Mark Crick, stated that the isolator may be the issue and to test by checking for voltage between the "center post" (alternator post based on my coaches wiring diagram and the markings on the Cole Hersee Co. No.48160 Battery Isolator) of the isolator to a ground. If there is voltage, that points to an issue with the isolator, probably a diode failure.

Sure enough there was ~13 volts.

In anticipation of this I purchased a Victron Argofet 200-2 battery isolator.

The wiring diagram for my coach shows an an Ignition Exciter wire going from the alternator to wiring that is energized when the ignition switch is on.

My question is the Victron unit has an "optional energize input" can that be ignored and use the input, output 1, output 2 and ground consistent with the existing wiring?

Re: Low voltage and Check engine Light

Reply #36 – March 31, 2024, 08:22:27 am

Quote from: twestrup – March 30, 2024, 05:11:57 pm

In anticipation of this I purchased a Victron Argofet 200-2 battery isolator.

The wiring diagram for my coach shows an an Ignition Exciter wire going from the alternator to wiring that is energized when the ignition switch is on.

My question is the Victron unit has an "optional energize input" can that be ignored and use the input, output 1, output 2 and ground consistent with the existing wiring?

IF your alternator is working correctly with the old isolator, then you can ignore the "optional energize input" on the ArgoFET. Hook the new isolator up just like the old one. Leave the alternator wiring alone - do not change anything. The "energize input" on the ArgoFET is only required if you convert to a Delco alternator. See the post by prfleming (linked below) if you want more info:

DelcoRemy 28SI alternator

Re: Low voltage and Check engine Light

Reply #37 – March 31, 2024, 06:56:11 pm

Some progress. When I got to the coach today, set high idle and checked voltage at the alternator and the alternator post on the isolator both readings were approximately 12.5 volts. At that point I started investigating the sense wire. On a wild guess I checked continuity across, what I believe is a fuse or auto reset circuit breaker. Circled in blue in the attached picture:

No continuity....when measuring ohms with my Fluke 117 it should OL. I started to take it out and naturally it fell apart....one post came out.

I do not know how to determine the size of the circuit breaker. I had a 15 amp, so I installed that. Set fast idle and bam 14.2 volts at the alternator and center post of the isolator.

I shut everything down, buttoned it up, put all the tools away and fired it up. I backed it out and suddenly got the check engine light and the Silverleaf gave me the same low alternator voltage.

Unfortunately I was too tired to tear it all apart again. I will leave that until tomorrow.

Any suggestions as to how to figure out the appropriate size of the auto reset circuit breaker, if that should have gone south again?

If it didn't go south any thoughts about how to continue troubleshooting?

I did not install the argofet isolator because I thought I had figured out the problem.

Re: Low voltage and Check engine Light

Reply #38 – March 31, 2024, 09:44:44 pm

Quote from: twestrup – March 31, 2024, 06:56:11 pm

Any suggestions as to how to figure out the appropriate size of the auto reset circuit breaker, if that should have gone south again?

The sense wire normally does not carry any significant amperage. A 15A circuit breaker should be fine. In many cases, there isn't any type of circuit protection provided on the sense wire.

If you continue to see that breaker opening, that would tell me that something is wrong inside the alternator voltage regulator, which is causing an abnormal current draw from the isolator battery post back to the alternator.

Something like perhaps a intermittent dead short.

Re: Low voltage and Check engine Light

Reply #39 – April 01, 2024, 10:05:58 am

Reference your questionable circuit breaker - there are three possible types. See link below:

Bussman Automotive Circuit Breakers - Wiring Products

Re: Low voltage and Check engine Light

Reply #40 – June 28, 2024, 10:43:48 pm

This is an old thread but I wanted to bring it to a true close. To save you from reading everything that transpired above - I had an issue with low voltage from my alternator that would intermittently cause a check engine light until the voltage rose again.

My alternator was an aftermarket Wilson DUVAC 200A and we found that the sense and ignition wires were switched. That helped the situation, but I would occasionally see CEL and my voltage never was very high per my dash voltmeter. I'd see 13.8V at my center lug on the isolator and 13.1 at the battery lugs. I had O'Reilly test the alternator and it showed a bad voltage regulator.

I didn't think it was truly bad - it was charging, just not charging at a high enough voltage. So, I bit the bullet and bought a Leece Neville since that's what came with the coach. I found a brochure in my paperwork and determined I should get the 4884JB. The thing I found interesting is that brochure listed the value for Voltage Adjustment as +1.0V.

That's when it clicked - these DUVAC alternators need a voltage offset to account for the drop across the battery isolator. I swear I came across a way to change the offset voltage on the regulator - but that would make sense to be the culprit to my charging woes.

Tonight I swapped out my alternator with the new one. Dash voltage is now excellent! Over 14V - I've never seen a value that high.

I'll hold onto the Wilson, maybe consider seeing if I can adjust the regulator get it replaced. I'll keep in tucked away in a compartment with my 41188 hydraulic pump, extra belts, fuel filter, and whatever else I add to The Kit.

Re: Low voltage and Check engine Light

Reply #41 – June 28, 2024, 10:59:14 pm

Quote from: stevej – June 28, 2024, 10:43:48 pm

That's when it clicked - these DUVAC alternators need a voltage offset to account for the drop across the battery isolator.

The purpose of the "sense" connection on a DUVAC alternator is to ensure that the alternator output voltage is high enough to correctly charge the start battery bank. If the sense wire is connected to the start battery bank (or another spot that reads start battery voltage) then the alternator should automatically output whatever voltage is required to properly charge the start battery bank. The fact that there is a voltage drop across the isolator diodes then becomes irrelevant.

Re: Low voltage and Check engine Light

Reply #42 – June 29, 2024, 11:10:44 am

Interesting - so maybe my old regulator was bad afterall.

What is function of the regulator set point voltage and voltage adjustment specified here?

Re: Low voltage and Check engine Light

Reply #43 – June 29, 2024, 12:15:00 pm

Quote from: stevej – June 29, 2024, 11:10:44 am

What is function of:
1. regulator set point voltage
2. voltage adjustment

Seems (to me) self explanatory.
1. The standard 4884JB regulator set point is 14 volts.
2. If, for some reason, 14 volts is insufficient then the set point may be increased by (up to) 1.0 volt.

Voltage Set Points | Smith Co Electric

Re: Low voltage and Check engine Light

Reply #44 – June 29, 2024, 12:54:34 pm

Quote from: Chuck & Jeannie – June 29, 2024, 12:15:00 pm

The standard 4884JB regulator set point is 14 volts.

And, that is perfect, as long as the SENSE WIRE goes to the chassis battery side of the diode-based battery isolator. That has alternator output around 14.6 (and should measure that at the center lug of the isolator which comes from the alternator B+).

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