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-   -   Question of the year - autofill? (http://www.airforums.com/forums/f44/question-of-the-year-autofill-37611.html)

SgtMunger 11-12-2007 06:35 PM

Question of the year - autofill?
 
Not even Airstream could help me here. I have a 1990 25' MoHo with an inoperative "AutoFill" system. Solinoid and valve work great (applying 12v with a battery), wires are fine all the way to the control panel. The AutoFill LED comes on but its not passing the 12 volts to the downstream side. As far as I can tell by eyeballing the circut design is there is a 16 leg IC, a PC mount relay (that seems to be operating), a 3 leg mosfet transistor(?) (#'s are P110 and a 839 on the face with a Motorola symbol, and along the top is 508838, non of which seem to cross refrence) then a diode on the output side. I'm getting 12v to the diode but not across it and out to the solinoid. When I jumper the diode the solinoid clicks and the system starts working but the transistor almost immediatly starts heating up to the point of smoking.
I cant find any circut design anywhere, and I hate having a nifty little feature like this that I cant use! Someone please help!!

TomW 11-12-2007 06:54 PM

Appearing stupid seldom slows me down
 
I have a travel trailer, not a moho.

What are you attempting to autofill?

Tom

lewster 11-12-2007 07:14 PM

Quote:

Originally Posted by SgtMunger
Not even Airstream could help me here. I have a 1990 25' MoHo with an inoperative "AutoFill" system. Solinoid and valve work great (applying 12v with a battery), wires are fine all the way to the control panel. The AutoFill LED comes on but its not passing the 12 volts to the downstream side. As far as I can tell by eyeballing the circut design is there is a 16 leg IC, a PC mount relay (that seems to be operating), a 3 leg mosfet transistor(?) (#'s are P110 and a 839 on the face with a Motorola symbol, and along the top is 508838, non of which seem to cross refrence) then a diode on the output side. I'm getting 12v to the diode but not across it and out to the solinoid. When I jumper the diode the solinoid clicks and the system starts working but the transistor almost immediatly starts heating up to the point of smoking.
I cant find any circut design anywhere, and I hate having a nifty little feature like this that I cant use! Someone please help!!

Hey Sarge,

I'm not familiar with their circuit design, but I've been around a number of MoHos that use a simple system:

If you have continuity in the wires to the solenoid and 12VDC power near the switch, why not just bypass the circuit board with a simple 12VDC circuit that will energize the fill solenoid using an SPST relay and basic switch on the control panel? You can always run an LED indicator from the downside of the switch to tell you it's on.:D

Simple is good!:D

SgtMunger 11-13-2007 10:37 AM

Quote:

I have a travel trailer, not a moho.

What are you attempting to autofill?

Tom
Hi Tom. Some of the MoHo's and I believe even the trailers around that time had an AutoFill system so when you were connected to city water you could hit a switch and automaticly fill your fresh water tank. The system would then shut off at 3/4 tank capasity. Neat system, just a poor design, or a cheap component used by whoever designed the circut for AS.
Quote:

I'm not familiar with their circuit design, but I've been around a number of MoHos that use a simple system:

If you have continuity in the wires to the solenoid and 12VDC power near the switch, why not just bypass the circuit board with a simple 12VDC circuit that will energize the fill solenoid using an SPST relay and basic switch on the control panel? You can always run an LED indicator from the downside of the switch to tell you it's on.:D
Thank you Lewster.
That thought had crossed my mind. The stock system has an auto shut off at 3/4 capasity, I assume it gets signal from the 3/4 LED and shuts off the relay, but thats where it starts to get a little more complicated for me since I dont know what other system (if any) uses that Circut board. I figured if I could get away with it I'd just replace the weak link (poor quality component) in the original.

SgtMunger 11-17-2007 09:00 PM

No other electronics guru's here? Any one with experience on the stock system?

GJ Excella 06-01-2010 04:46 PM

I have a 1989 32' Excella, after 28,000 mile last year, both wires to the Auto fill solenoid became disconnected. Does it matter which wire goes where?

Thanks, Joe

TomW 06-01-2010 04:57 PM

Normally "no", but
 
Quote:

Originally Posted by GJ Excella (Post 855618)
... Does it matter which wire goes where?

No... Usually.

The solenoid itself could care less. "Usually" because some careful designers hang a diode across the terminals of a DC circuit to cut down on arcing across the contacts. If the wires are connected incorrectly in that situation, you will either blow a fuse or toast the diode.

If the only thing you see is two terminals where two wires go, then you are okay. Hook your wires up, and move along.

But if there is a "+" or "-" mark on the terminals, then reply back. A picture would be nice.

Tom

HiHoAgRV 06-01-2010 07:36 PM

Quote:

Originally Posted by TomW (Post 855625)
No... Usually.

The solenoid itself could care less. "Usually" because some careful designers hang a diode across the terminals of a DC circuit to cut down on arcing across the contacts. If the wires are connected incorrectly in that situation, you will either blow a fuse or toast the diode.

If the only thing you see is two terminals where two wires go, then you are okay. Hook your wires up, and move along.

But if there is a "+" or "-" mark on the terminals, then reply back. A picture would be nice.

Tom

Mine does not have a diode, therfore it's not critical on the connection.


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