Ford Starting /House Charging Question UPDATE Test

[BFL13]

New test 20 Jan.
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The solenoid in the sig rig only closes the line between the engine battery/starter/alternator and the house batts when the engine is "on".

What happens when you turn the key to start the engine? At some point the solenoid closes so the house and engine battery/alternator are linked and the alternator can charge the house batts.

Is there a point at which the key is turned and the starter has not yet cranked the engine, when the house and engine batts are all on line to provide the amps to operate the starter? Or is it just the engine batt doing that, and the house batts are connected to the alternator afterwards?

I know the alternator can't do anything until the engine is running to turn the belt, but is the line connected before that?

Thanks.

[wa8yxm]

If you have a one way isolator.. Trick-l-start device provides the other way.

[BFL13]

Yes, the main thing is to "know your rig", which you have done. Then you can adapt to whatever happens with the set-up you have. Also tells you what changes you might need to the OEM set-up if you have a scenario not covered.

If you are running normally at just over 13.6 once the alternator warms up etc, then if you power an inverter from the engine battery, that could bring it below 13.6 loaded voltage and now no "alternator charging" to the house side.

Some MHs have inverters that operate from the engine batt (ISTR to run the overhead TV above the cab)

[PatJ]

BFL13 wrote:

how is that 20 sec delay better than just waiting for the spring-loaded key to go back to "ON" from "START" ?

If the house batteries are very low, it may be nice to have the engine settle back for a bit after a cold start before it's hit with that large charging load. But I don't know if it's actually any "better" or just my perception.

But if for some reason the chassis were placing a heavy load on the charging system and it dropped below 13.6, the charge relay would shed the house batteries to focus on the chassis. I can see value in that scenario, even though it is unlikely.

[BFL13]

PatJ wrote:
On my 2019 Ford C the charge isolator relay is under the coolant overflow bottle. It has a delay built in so the engine has to be running for about 20 seconds before it ties the chassis battery and house bank together. The manual explains it needs to see charging voltage >13.6V on the engine side which starts the 20s timer. Any time voltage on the engine side drops below 13.6 it will untie the batteries and wait for 13.6 again to restart the timer. You can hear this click from the driver's seat after starting the engine. Emergency start switch bypasses this delay.

From a post in thread in another forum that I linked earlier:

"I run a dumb solenoid wired to come on with the ignition (not a fancy IBS system - which is just a dumb solenoid with a little brain to decide when to energize the solenoid). Done deal"

So the 2019's come with an IBS OEM?

EDIT--how is that 20 sec delay better than just waiting for the spring-loaded key to go back to "ON" from "START" ?

[PatJ]

On my 2019 Ford C the charge isolator relay is under the coolant overflow bottle. It has a delay built in so the engine has to be running for about 20 seconds before it ties the chassis battery and house bank together. The manual explains it needs to see charging voltage >13.6V on the engine side which starts the 20s timer. Any time voltage on the engine side drops below 13.6 it will untie the batteries and wait for 13.6 again to restart the timer. You can hear this click from the driver's seat after starting the engine. Emergency start switch bypasses this delay.

[MrWizard]

Can't burn the points
But you can drain the battery, by having power to circuits that would otherwise be turned off

[enblethen]

I would not come off the alternator. I would look for a circuit that is hot in run such as wipers, radio heater and the like. Use a fuse tap from fuse block. Some rigs have fuse block under hood with switched power.
My reasoning is if something happen in alternator tap, you could have damage to charging system.

[BFL13]

"Perhaps it would achieve the same thing if the solenoid's ignition wire got its power directly from the alternator"

My idea there would work for me, but wouldn't for those with the rocker switch jumper

[dougrainer]

docsouce wrote:
If my house batteries are very low and will not turn my generator over, can I engage the "engine emergency start" button to start the generator?Not trying hijack the thread, but it seems to be related.

Yes, as long as there is enough coach battery voltage to engage the relay. Its done all the time on Diesel Pushers. A lot of Diesel Pushers use the Chassis battery to start the Genset. Doug

[BFL13]

New test for just when "on" engine off (not started yet)
MH on shore power, house at 13.8v, no charger on engine batt.

Voltmeter on three solenoid posts: engine side, ignition wire in middle, house side for positive and engine battery neg post for neg.

"OFF" - 12.77, 0.00, 13.76
"ON" -- 12.82 rising slowly, 12.39 rising slowly, 13.04 (blower fan running, dash warning lights on)

So that answers that one. My MH does not have that rocker switch for connecting house to engine so can't answer any of those questions.

Thanks to all for the help with this for how my MH works for that.

[BFL13]

I will re-check whether my charging solenoid closes when the key is turned to "on" and not yet turned to "start"

Yesterday I had the voltmeter on the small wire that goes in the middle (sometimes seen called "ignition wire") and it only showed battery voltage coming onto it after the engine started, but I will re-test. I had the pos probe on the ignition wire terminal in the middle of the solenoid and the neg probe on the battery neg post.

This time I will also compare battery and house voltages to see if there is any action once the key is turned to "on" and left there.

When the starter is started the blower etc quit to reduce the draw on the engine battery and then the key goes back to "on". So it seems that power cut to the other things includes cutting power to the "ignition wire" on the solenoid to open it, and then it closes when the key goes back to "on" and power is restored to the other things too.

So even if the solenoid is closed when you go to "on" that still leaves only the engine battery to start the starter and then after that the house batts are put in parallel with the engine battery.

I saw no voltage drop on the house batteries when the engine is starting, only the rise after the engine got going. If the solenoid does close when just in "on" and engine not running, then I would not see that at the house batts, because there would be no load from the starter.

Perhaps it would achieve the same thing if the solenoid's ignition wire got its power directly from the alternator.

I remember that you are not supposed to leave the key in "on" with the engine off because it will burn out the points. AFAIK there are no points anymore but vague on that. So I hope today's test does not burn my points if I have any. I will report results of the re-test later today.

[maillemaker]

If my house batteries are very low and will not turn my generator over, can I engage the "engine emergency start" button to start the generator?Not trying hijack the thread, but it seems to be related.

I think so. But I can't do it on my rig because my arms aren't long enough. 🙂

My 3-way rocker switch with MOM (emergency start) is on the dash by the driver. The generator start switch is either on the generator or back on the stove vent hood.

My generator starts from the engine battery. I would have to get a helper to hold the MOM switch in order to start the generator from the engine battery.

A better solution would be to use the house batteries to start the engine, and then start the generator using the current provided by the alternator (and let the alternator charge up the engine battery).

[maillemaker]

How can the key be in run and the engine not started?

If the engine were running and died by some other means than using the key to turn it off, (out of gas, pop clutch, etc.) then the engine could be off but the key in RUN.

In normal operation, however, the engine will be running when the key is in the RUN position. But there is also a START key position and this is different from RUN. Many times things are disconnected in START that are connected when in RUN. This is so the engine starter motor gets all the current. You might notice your radio turning off when starting, for example.

[docsouce]

If my house batteries are very low and will not turn my generator over, can I engage the "engine emergency start" button to start the generator?Not trying hijack the thread, but it seems to be related.