Community Forums

Rocketman3 · 07-13-2020, 12:31 AM

Hello everyone,

On my 2000 Dynasty, I have installed 800 watts of solar. Sometimes, I get an issue of the RPM gauge dropping to zero and the alt fail light comes on. After that happened, researched it and found if I added a load (turned on my headlights), the issue goes away.

My understanding is the solar is putting enough juice into the system that the alternator doesn’t see the need to make any more. The RPM is tied to the alternator- so the gauge goes to zero. (I could be wrong here please correct me if I am).

I only see three systems that tie to both The chassis and house power: the blue battery isolator, the chassis battery charger, and the solar charger. Does anyone know which system is letting the house power override the alternator?

That is the engine battery charger’s job, but then wouldn’t it happen all the time?

Thanks for everyone’s help!

twinboat · 07-13-2020, 02:12 AM

The chassis battery charger should be the Lambert 415 battery maintainer.

That takes house battery voltage and sends it to the chassis battery, BUT only when the house battery is being charged. Its doing its job.

It doesn't happen all of the time because the alternator output is dependent on chassis battery voltage. The house battery will be getting equal charging voltage thru the isolator and the 415 doesn't come on.

Adding solar to the house battery raises its volts higher then the chassis volts, causing the 415 to send some to the chassis battery.

When the voltage regulator in the alternator senses more volts then its set to output, it believes its not working and turns on the warning light.

This all should only be happening when driving and the house batteries are fully charged bringing the solar controller into float mode. If your float voltage is adjustable, turn it down one or two tenths of a volt and see if that clears it up.

Ivylog · 07-13-2020, 10:12 AM

Yes, on many Monaco’s the alternator is your RPM source... why you rebuild the alternator instead of replacing. Running the generator while driving will do the same thing sometimes...inverter/charger is charging house batteries and engine batteries confusing the alternator. Running your headlights may solve the problem... not a bad idea to have them on as long as you do not forget to turn them off.

You could add a switch to the wire that’s engauging your boost solenoid (before the wire from the boost switch) separating the two systems.

creativepart · 07-13-2020, 10:17 AM

What solar controller do you have installed? All the current ones I'm aware of are smart enough to not send any solar charging to the batteries when ANY other device is charging the batteries.

Your solar charge controller should read your battery bank's voltage and when it sees the 13 to 14v from your alternator (or inverter/charger or converter/charger) that it stops attempting to charge your batteries even if it's the middle of a sunny day.

Timaz · 07-13-2020, 01:47 PM

Quote:

Originally Posted by creativepart

What solar controller do you have installed? All the current ones I'm aware of are smart enough to not send any solar charging to the batteries when ANY other device is charging the batteries.

Your solar charge controller should read your battery bank's voltage and when it sees the 13 to 14v from your alternator (or inverter/charger or converter/charger) that it stops attempting to charge your batteries even if it's the middle of a sunny day.

This is true, But I put in a solar disconnect and just shut the solar down when I have the engine running so I don't have this problem.

Tim

YC1 · 07-18-2020, 09:23 AM

Many rv's have a generator "lockout" while the engine is running.

That is, the generator runs the converter and charges the house batteries but the combining system does NOT combine under those conditions.

While connected to shoreline and starting the engine often gives me an Alt Fail light. The "lockout" does not function under those conditions.

This most often happens when the battery banks are full. So there is no load on the systems. Turning on my headlights is enough to stop the Alt Fail light.

All this said, I have never seen the Tachometer not work.

RVingNow · 07-18-2020, 10:20 AM

I've never heard of this issue in an RV. It happens on my boat quite often and I just turn on some load to get the alternator to start producing. Interesting.