What is the correct way to check to see if the engine alternator is not charging the house batteries? 

I know there is a solenoid that handles the charging of both the engine and house batteries.  On my Journey, I think the solenoid is not working correctly and not allowing the house batteries to charge. 

On a recent cross country trip, running my TV and in motion satellite dish, after several hours the batteries used up enough juice that the TV  and dish turned off requiring running the generator for a while to re-charge the batteries.

It seems to me that the 165 amp engine alternator should be able to keep up with this minor load on my 3 Group 27 house batteries.

So I suspect the solenoid, but before I order a new one, I'd like to check it out.
Hence my question, what should I test for?

Best regards!

Somewhere you have a readout of your house battery voltage, often by the battery disconnect or your inverter/charger display.  When disconnected from shore power these should read battery voltages somewhere around 12.5 to 12.8 volts or so.   Now start your engine and soon, it might be a few minutes, the voltage will jump into the 13 plus range if the alternator is charging the batteries. A multimeter on the battery leads set to read DC voltage also works if you do not have a voltage display.  When on shore power your inverter/charger should be keeping the battery voltages around 13.2 to 13.5.
It might be a loose connection instead of a solenoid if the alternator is not charging the batteries.

As an aside a rule of thumb with alternators is to not run them long at over half load, so a 165 amp alternator should not run more than a few minutes providing more than 80 to 85 amps of charging.  A TV or refridgerator on electricity (some inverters are wired this way or change it to not use propane while driving down the road) is way under these numbers, but don't run your microwave/convection oven while going down the road expecting your alternator to handle the inverter load without burning out your voltage regulator. 

Again, Bill, thank you for sharing your knowledge.  When I meet you on the road one of these days, I'm buying!

Best Regards!

Six years ago I knew squat about all this. I have learned from others and still have a lot of learning to go.

(You can also tell that I have had a lot of computer time today.  The reasons that kept us home finally were completed, phone calls and email, and we did get a chance for a nice scenic drive and even had dinner out here in Coeur d'Alene, ID.)

-- Edited by bjoyce at 23:19, 2008-07-14