Aux power from truck to fifth wheel

2006 Ford aka 6l Powerstroke?
Those engines have a program (design to save glow plugs) that will not activate the alternator till engine gets warm, what can be several minutes.
My guess you were reading at that time.

pop hood. Read + to - on battery record voltage

go to plug and record + to - and record voltage

If not the same trace from plug back to battery and find the problem

When I got a new alternator for our 1992 GM van, the voltage increased considerably. It seems to me the "best" charging voltage has been increasing lately and alternator manufacturers have turned it up a notch. (Contrary to the otherwise excellent thread linked in a previous post, the voltage is controlled by changing the current flowing into the alternator electromagnets.) I wonder how vehicles with computer controlled alternator voltage decide what voltage to use? Ideally they would monitor current in and out of the battery to calculate the % of full charge and run 14.5 volts until 80 or 90 % charged - ending chronic undercharging for vehicles that mostly do short trips in a cold climate.

Before solar when we were dependent on engine charging (and after losing a pair of batteries to undercharging), I checked out the wire from engine to house on our motorhome and found a drop of half a volt across a joint. Fixing that made a significant increase in the charging current. Strangely, the charging current traveled an extra 20 feet each way to a battery cutoff switch at the door, which lost more than half a volt, mostly in the switch. The solution for that was to connect the engine charging wire directly to the battery.

The charging is through the Ford auxiliary battery charging system which includes a relay to connect only when the engine is running. I found no voltage drop in the relay but systems with a diode to prevent current from flowing backward from house battery to engine drop at least half a volt.

I ended up with house battery charging voltage half a volt below engine battery, up to 5 amps of engine charging, double what I had before. Certainly not enough to power a fridge in DC mode but it helped.

Thanks one and all! I knew I could count on you guys/gals.
I need to go back in a bit n test again. The truck wasn't running very long when I checked, and, get this, my dome lights had been on for three days, since I cleaned out the inside of the truck. It's a wonder it even started!
I will compare to battery voltage.

Depends a lot on the current temperature and charge conditions.
It should be very close to what the vehicles batteries are showing. The colder it is, the higher they will be. So there is no one answer, you need to compare it to the trucks batts.

oldtrojan66 wrote:
Cannot find any positive results from search for this question.
How much voltage should be coming from the truck (when running) to the aux power "in" at the plug in?
I have a 2007 JAYCO 36 RLTS and a 2006 F350 dually. I believe the plug is factory and the pins are wired correctly. From 1 o'clock position to 7 o'clock position I read 11.67 VDC with truck running.
Seems that's not enough to provide even a trickle charge going down the road. Any thoughts?

Thanks in advance, david

The voltage at the seven way typically is only slightly less than at the TV battery. Example; 13.6 at battery and 13.4 at seven way.

First verify you are checking the correct pin and ground of the truck connector.
Voltage s/b same as truck battery voltage with vehicle running.

I assume the trailer is not connected when you are checking voltage. Trailer could cause voltage to sag if the load is high.

oldtrojan66 wrote:
Cannot find any positive results from search for this question.
How much voltage should be coming from the truck (when running) to the aux power "in" at the plug in?
I have a 2007 JAYCO 36 RLTS and a 2006 F350 dually. I believe the plug is factory and the pins are wired correctly. From 1 o'clock position to 7 o'clock position I read 11.67 VDC with truck running.
Seems that's not enough to provide even a trickle charge going down the road. Any thoughts?

Thanks in advance, david

You should get 13.6 volts w/truck running. Test the voltage at the power point right of heater controls. Just checked my 2004 F350 and got 13.6.

good luck



C.B.

Same as regulator output. If not start looking for a frayed wire or loose connection.