Hi, I am new here, and about to sell my E350 (E360) 1987 Travelaire Motorhome. The following text s what I plan to provide the automechanic with. The complexity of what happens to the electrics is baffling. Here we go:
Ford air conditioner defect

The Ford air conditioer had been working well during a trip from Canada to Mexico, 2010. Cooling agent was added in Puerto Vallarta.
The a/c was never switched on until spring 2013.
The a/c was switched on while the vehicle was still parked. Then the following happened: About 300 meters driving the vehicle stalled. Reason: No fuel or no ignition - apparently. The fuel tank was full.
Observations:
On the front panel (dash board) the 2 green arrows Left/ Right indicators and the blue Head Light were continuously lit up (on) when ignition switch was on.
Later in the repair garage it was found the fuel pump was burned out. (This was a new fuel pump installed 6 month earlier ). Circuit testing brough a power (on/off) indication at the fuel pump positive feed wire when the a/c was switched on/off. How this happened and why it burned the fuel pump is what I did not understand.
The fault in the air conditioner seems to be the motor, according to the mechanic's opinion. There was no a/c spare part available at the location.
The a/c was disconnected (inl. fan) and not reconnected since then. The front panel indicators no longer worked the wrong way, they all are normal. The fuel pump / level senor assembly was replaced and work normal.
Attention: The person who wants to repair the Ford a/c must ascertain the a/c electrics are ok before reconnecting and switching on the air conditioner. There is no need to risk burning the expensive fuel pump motor.
___ end of message to auto mechanic ____

So far so good - confusion active. The a/c motor has not been checked as to its condition, burn out is assumed, nostril concluded.

Remote possiblility, unchecked: Rat building nest near the air intake of the a/c, resulting in blocking - burning. Does not explain how indicastor bulbs and fuel pump get power from a/c.
I could imagine fuel pump burn out when engine off and pump powered without being able to move fuel. However, the vehicle engine was running for several minutes, then driven for about 1000ft when the "no fuel" symptoms hit.
Looking forward to help. Thanks.

 

Just about any time you get crazy things like this happening there is a ground problem.
This can usually be found by doing voltage drop testing or just checking all the ground wires and connections. Checking them involves removing them , cleaning them and reinstalling them. Just looking at them does not do it !!
If no poor connection is found then you need to do the same thing with the voltage supply to the fuse panel and from the fuse panel to the A/C , fuel pump etc. Low voltage will burn out a fuel pump motor, but you should have noticed some performance problems while the condition existed.
Have you noticed any other things not working right ?

 

<<Low voltage will burn out a fuel pump motor, but you should have noticed some performance problems while the condition existed.
Have you noticed any other things not working right ?>>

Battery was fully charged. No other performance drop noticed.
Can not see how voltage drop on +- side of fuel pump could be related to a/c on/off switch.
Can not see how lack of ground connection on a/c could power the green Left+Right flashers non-flashing, and the blue head light indicator.
Can see a locked ful pump burn out due to fuel pipe blocked or voltage too low to turn its motor.

Driven several 1000 miles since, no fuel / start problem.
Will search for poor contacts, thanks for your help.

 

If you connected a voltmeter to the fuel pump positive terminal and turned on the A/C , if there was any resistance due to poor connection in the supply to the pump you would see a voltage drop.

If ground for A/C system is with high resistance, system will take whatever path it can to ground and in this case it could be through the lighting circuit.