Engine charging House Batteries?

Is there an easy way to check and see if the engine alternator is charging the house batteries?  I've thought of measuring the voltage across the house batteries after unplugging shore power and before starting the engine, then recheck after the engine is running... not sure this would work tho.

The reason I ask is that the house batteries alarmed after being underway for several hours with the inverter running the fridge.  I've done this before with good results but these are new house batteries, 3 12Volt batteries instead of 4 6 volt batteries...  less capacity but I thought it would be enough for us.

thanks for any insights.

Taos,
Yes that is a good way to check that your alternator is charging the house batteries.

taoshum said:

Is there an easy way to check and see if the engine alternator is charging the house batteries?  ...

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Use the HOUSE / ENGINE battery voltage meter in the OnePlace panel.  With shore power unplugged you can check the HOUSE battery voltage, then with the engine running check it again--it should be approximately equal to the ENGINE battery voltage (somewhere around 13.5V).  If it isn't your BATTERY MODE SOLENOID has probably failed and needs to be replaced.

This old thread from over on iRV2.com has a good discussion of the problem & fixes: Yet another solenoid bites the dust!

What Chris said! Wow, that thread you referenced was one I started ten years ago  8) .

Is this "solenoid" near the batteries?  the existing one lasted for 11 years if this is the problem...

I guess I could get a replacement and try it.  Where does it fail, a related figure attached.

On your Meridian it's up front behind the front hood (see page 3 of the Front End Wiring Installation diagram for your coach).

taoshum said:

...  Where does it fail, a related figure attached.

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I performed a post mortem on one of my failed Trombettas, I took pictures and posted it in a thread either here or iRV2 - I forgot. Anyway there was no "smoking gun' other than discoloration on the wrapping around the coil itself indicating heat. The coil resistance was very low but I don't know if it was out of spec since I didn't have a new Trombetta to compare readings (I replaced the dumb Trombetta with a 'smart' Blue Sea solenoid.)

My expectation was to find the contacts themselves burned/arc'd up but they looked fine.

John Canfield said:

I performed a post mortem on one of my failed Trombettas, I took pictures and posted it in a thread either here or iRV2 - I forgot. Anyway there was no "smoking gun' other than discoloration on the wrapping around the coil itself indicating heat. The coil resistance was very low but I don't know if it was out of spec since I didn't have a new Trombetta to compare readings (I replaced the dumb Trombetta with a 'smart' Blue Sea solenoid.)

My expectation was to find the contacts themselves burned/arc'd up but they looked fine.

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do you recall the p/n for the blue sea solenoid?

The one I used is not available. In my signature is a link to my RV project page - look for the solenoid replacement project. There are suitable replacements available though at Blue Sea.

Just FYI, my silver contact Trombetta with a couple of inline resisters to drop the activation voltage a bit (see previously linked thread) is still going strong ten years later...

Just to verify, is this the suspect solenoid... pic attached.

Is there a VOM measurement that would verify that this solenoid has failed?  I'm only asking because it will be a real challenge for me to replace it and others have mentioned that there might be other causes?

I REALLY appreciate the comments, tips, links and help from everyone!!!!

Could be. If you looked at my web page write-up where I changed mine out, the house disconnect solenoid and the battery mode solenoid (the one of interest here) are next to each other. Maybe that will aid in your identification.

Yes, that's the suspect solenoid.  You can see that it matches the location & picture in the earlier linked diagram.

taoshum said:

..Is there a VOM measurement that would verify that this solenoid has failed?  I'm only asking because it will be a real challenge for me to replace it and others have mentioned that there might be other causes?...

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Problem is I don't know what the coil resistance should read or how much current it should draw. With the solenoid operated, there should be almost zero resistance across the contacts.

However these are notorious for failing and the common symptom is the house bank fails to charge while running the engine. I had maybe three of the Trombettas fail before stepping up to a better product.

[size=14pt][size=12pt][size=10pt]My continuous solenoid failed last year just before my trip to Florida so I went to NAPA and got one for about $40.  Everything worked ok after that.

John Canfield said:

What Chris said! Wow, that thread you referenced was one I started ten years ago  8) .

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And that thread has helped numerous people John. For years I was under the impression that the engine was not supposed to charge the house batteries  until I stumbled across that thread and others and replaced the solenoid.
Thanks again.

Bill

[...]being one who likes to troubleshoot failures, I carefully disassembled the "broken: solenoid and found that all I needed to do was to clean the copper rings and terminals.  The problem was surface oxidation and was easily fixed.  A quick bench test proved successful with full continuity across the charging circuit when energized with a 12v source.[...]

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When I tore down one of my failed solenoids, I fully expected to find contacts that arched over and carboned up but they looked okay. Anyway, the Blue Sea solenoid is a huge step up from the dumb Trombetta and it has lasted for many years.

One other point, the battery mode solenoid and the house solenoid are behind a closed metal box, with the solenoids engaged they produce heat along with the inverter/charger. Since my electrical bay is under the bed, I installed a 12V bilge blower that forces air into the compartment and helps to moderate the temperature. I think that's a significant factor for adding life to the stuff in the bay.

Bill N said:

And that thread has helped numerous people John. For years I was under the impression that the engine was not supposed to charge the house batteries  until I stumbled across that thread and others and replaced the solenoid.
Thanks again. Bill

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Others helped me a bunch when we got started so it was fun to 'pay it forward.' Thanks for the kind comments.

FWIW, today I did some "diagnostics"...  with shore power "ON"; I measured no voltage across the activation terminals.  About 12.5 VDC from the left high current post to GND.  About 13.3 VDC from the right high current post to GND.  With the shore power "OFF", about the same.  The "trickl" charge box indicated that the "engine batteries" were being charged.  With shore power "OFF" and engine running. there was about 13.5 VDC across the activation terminals of the solenoid, left side high current post still at 12.5 VDC while right high current post was even higher 13.8 VDC.  At this point I'm convinced that the solenoid did not activate.  So I took a soft mallet and banged (firmly but not hard) on the solenoid.  I heard it activate with a loud "clunk" and then both of the high current post voltages were about 13.8 VDC.  Inside on the panel, the house batteries and engine batteries were about the same.  So I took the coach out for a short drive and it seems to be working "normally".  Note that there was no voltage on the activation terminals with the ignition key in the "ON" position but after the engine was running there was voltage.

I'm thinking the plunger was "stuck" or some other scientific term to describe non-activation and with a little help it started working... friction?  Corrosion?  Weakened spring? 

Time to replace it but I'm not in such a quandary or worry.  Again, thanks for all the comments, suggestions, knowledge and patience.

taoshum said:

....I'm thinking the plunger was "stuck" or some other scientific term to describe non-activation and with a little help it started working... friction?  Corrosion?  Weakened spring? 
..

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One of those things. The magnetic field produced by the coil could have somehow weakened, not sure how though. Glad it's definitely diagnosed but you really should replace it as soon as possible.

New solenoid installed; all fine once more. Royal PITA to get access though.

BTW:  I used a spare battery to activate the "old" solenoid on the workbench and then measured the resistance across the high current terminals...open is open of course but closed showed a variable resistance of a few ohms to about 90 ohms... repeated cycles were the same.  On the new solenoid, the resistance was always zero ohms.  I'm thinking that the "old" solenoid developed some contact resistance, pitting or whatever.  It did close nonetheless, easily.