Hello I am new . I am having problem with the charging system on the Ford part of the motorhome. I have replaced the alternator,Voltage regulator (both have three wire). I have also replaced the starter soliond. I have a 3 wire regulator and need to use a jumper wire from the s terminal to the field terminal to get the alternator to make 16 volts but will not run with the positive cable of the battery. The odd part is the coach has 2 batteries and an Isolator (which is new) There is a switch on the dash when pushed in allows the coach batteries to start the motor. When I push in the switch and hold the motor starts and and if I hold it I can go down the road just like the alternater was working. I acually drove about 100 miles to get home. I need to let the generator which is using the inverter to charge the batteries on the coach. Does anybody have any ideas on why the ford charging system will not work? Does the alternator route through the isolator?

 

Welcome Broke 460!

What started the situation where you ended up replacing the entire charging system???

Is the fuseable link on the output side of the alternator intact?

Are you sure that your engine's battery is fully charged?
Take it out and have it load tested.
If it checks out then you need to insure that the ground cable is in good condition and firmly attached.
Because, it sounds as if that battery is not in the circuit at all...

If the battery is dead be sure to charge it first, before trying to let just the alternator charge it. Putting that much load on can damage the new components of your charging system.
Without some current to excite the alternator it will not put out the +/- 14V it was designed to.

Something is definitely wrong because once started the alternator should be able to keep the engine running and you should never need to be crossing wires from the regulator to get output.
16V is way too high and if it doesn't burn up the new alternator it will quickly boil or warp the plates in the battery. (if it hasn't already)

The whole point of the isolator is to allow the alternator to charge the coach battery (ies) while the engine is running but not allow engine battery to be drawn down by the coaches demand for power with the engine off.
You are getting home by overriding the isolator and backfeeding the coach batteries into the ignition system. (total loss)

So, if this is what you are asking, then yes the alternator output does ultimately feed through the isolator.

Motorhome chassis are somewhat unique and I'm no expert.
Some on this forum are, and may have a better answer for you.

 

Hay Jim thanks for the help!!!!
The fuseable is up by the starter seliond and is in good shape. I started replacing the charging sysytem because. When I left home the charging work according to the gauge and I could remove the positve cable. About a hour later the motor went dead and I had no power. I put in a battery out of a crawler I was hauling which got me to a part store. Thats when I started replacing the charging system. I am home now and replacing the negitive cable and see what that does. I just stumbled on to running on the coach batteries but that what got me home. I have already charged the battery. Lets hope it helps. Thanks in advance

 

So you started out on a trip and within an hour the battery was discharged to where it couldn't even support the ignition?
I think there's a short or some other load on the battery. I have driven much longer than that with no belt, but I wasn't driving with lights or blower on.


This is a very basic diagram of the 1G charging system.