Heater fan switch only works on high

HI/LO Freon switch is first or relay stays off line 5.7L V8 GAS OR DIESEL? 2 ARE DIESEL OF 3.
scan the PCM first. p0646?

THE PCM CUTS THE CLUTCH FOR MANY REASONS;
HI/LO SWITCH TRIPPED
CAB BLOWER DEAD
ENGINE OVERHEAT (OR SENSOR FOR THAT TELLING A BIG LIE)
ENGINE OVER LOADED RUNNING WOT.
EVAP CAR ICE UP SENSOR. TRIPPED.
FUSES.
NO SCANNING PCM WE MISS THE BOAT .
WAY TOO COLD OUTSIDE, SENSED.
ENGINE RAD FANS DETECTED DEAD.
CLUTCH IS BAD OR SHORT OR OPEN COIL
RELAY BAD.
THE NEW RELAY SHOWS 5 PINS. SO IS BIG CLUE THERE.
CAB FUSE BOX NOT ENGINE BAY
LEFT SIDE COLUMN OF RELAYS
TO9 LEFT SPARE RELAY,FOG, ASD ,CLUTCH
4 DOWN LEFT

cab heater? there are 3 fans, engine,cab heat and A/C. so....
a stuck CAB switch is a bad switch. easy huh?
if the switch only works on high but does move, that is a bad heater fan Resistor block. (usually bolted to fan hosing as it is air cooled this part)

1996 Dodge Ram 3500 diesel Standard Payload, lbs.ext. cab long bed 5151, ext. cab short bed 3915, reg. cab long bed 5340, reg. cab short bed 2372.---------------------------------------------------------------------------------------
Multi-Di@g Access J2534

A mechanic would check the freon charge, then for power in the ac compressor circuit starting at the relay.

The rear brake lamp is a whole module. Get the whole unit for left and right no after market one the pins are not always correct

sounds like the turbo bearings are going.You could use molyslip oil additive,but this is only to coat the bearings it will not stop the noise for long....

it a control switch on your dash

check the reostat which is a resistor that controls the fan speed and also check the wiring to both the reostat and the heater motor

Very likely stuck door jamb switch. Replacements are cheap and available at most parts stores.

Two actuators can be accessed (enough to move them) without removing it. One is on the bottom of the HVAC unit on top of the trands hump, you will probably have to remove the airbag module and cover to get to it. The other one is on the driver's side of the HVAC unit about half way up. Remove the driver's side knee bolster and you should be able to see it.