MCI 9 Heat/blower stuck on

[samiam]

I am working on my first bus/first conversion.

Got an amazing price on a MCI9 up the road, guy had already pretty much stripped it, converted it with 7 rv windows, and sealed up everything with 2" iso board and plywood except the center ceiling (pieces are there just not in) or redoing the floor.  Put in two new batteries and some water (going to need to empty out now before it gets cold) and it made it up and down the hill back to my place without any accident; I was shaking by the end though!  Needs a lot of love and two new tires.

So almost done the sealing the exterior (over 120 hrs of caulking alone) and about to really work on the inside but whenever i put the power on, the heat and blowers stays stuck on.  Didn't really mind it in the summer so definitely don't mind it now, but it's annoying.  I've looked at the service manual and fuse/junction box outside the driver window and I've tried disconnecting one wire for the heater relay but that didn't seem to do anything.  Any ideas?  I'll add some pics of the box because it looks different than the manual.

[gumpy]

Stuck relay. Contacts welded shut.

[buswarrior]

wires carelessly cut and shorted?

happy coaching!
buswarrior

[samiam]

yeah i figure it's a stuck relay, which one though?

[gumpy]

Probably a bad switch.  Could be the Evaporator Motor Magnetic Switch in the A/C J-box in the first bay, left side.

Page 7-46 in Section 7, Heating and Air Conditioning schematic. Circuit 47, Red/Yel, 16 gauge wire from switch to Stud 18 in FJB. Then 47 Red/Yel, 14 ga wire from FJB Stud 18 to AC-Jbox Stud 14.

[bevans6]

The main coach heater fan motor is actually called the evaporator fan, and has two speeds.  Low speed is for the heater function, the coach heat relay has nothing to do with controlling the fan, all it does is control the amount of heat by turning the electric water valve on and off.  The relay you probably took a wire off of is the right hand relay in the front electrical panel, so you can probably put that wire back.  The heater fan function gets it's power from a 15 amp breaker in the rear electrical panel, through the blower cut-in relay, up to the front switch panel and through the coach AC/Heat switch, from there back to the AC electrical panel (roof of the forward luggage bay, driver's side) and to the low speed tab on the motor (the motor is inside the air handling compartment behind the front wall of the forward luggage bay).  The AC function of the motor is the high speed tab on the motor, controlled by the same Coach AC/Heat switch on the switch panel, but it switches the Evaporator Motor Relay, which is a big relay inside the AC electrical panel.  That relay is fed by an 80 amp relay, so high current and be careful.  

First things first.  By "turn the power on", what do you mean?  The dash switch, or the main battery disconnect switch?  If you mean the main battery disconnect switch (really big switch, forward wall of the front luggage bay, passenger side) and the big heater fan motor under the floor in the middle of the bus, then it's probably the evaporator motor relay.  If you mean the big main heater motor comes on when you turn the dash master switch on, we need to go further.  First, check that the dash switches are in the correct positions.  The driver's AC switch should be all the way down, the driver's defrost switch should be in the middle position, the coach AC/heat switch should be in the middle position.  Is the main bus heater motor coming on, or is the drivers heater/defrost motor coming on?  If it's indeed the main bus heater fan motor, it is enabled by the blower cut-in relay, which only allows the fan to come on if the bus is running and the alternator is generating electricity.  No alternator, no heater/air conditioner fan.  If the main heating fan is coming on with the engine off, first guess is again the evaporator motor relay in the AC electrical panel, so disconnect one of the big wires and see if the fan turns off.  If the dash defrost/driver's heater motor is what is coming on, check it's switch is in the middle position, and check the driver's blower relay, which is in the front electrical panel.  Just pull the relay out and see if the motor turns off.

This is getting too confusing, so - which heat fan is coming on, are the dash switches in the correct position, and what do you mean by "turn on the power"?