Ok I installed a new blower motor and new resistor (rock auto), Installed Friday. Checked everything working good

 

Previously my AC Blower would sometimes not go on, then go on a few miles or more down the road

 

Sunday after a trip to the store , Start truck to head home and the blower motor doesnt go on again. Damn it !

 

I mess with on and off switch and speed switch nothing, pull into get fuel about 1 mile away and the blower goes on.

 

Worked fine the rest of the way home. At home I pulled and reinstalled both the relay (under the hood) and the fuse(side of dash) everything good and blower is working fine now still

 

I'll see if I still have the same problem as I drive my truck. .... but any ideas what else would be the problem?

 

Rick

 

 

Edited September 16, 20186 yr by GSP7

You're going to have to do some simple diagnostics.

Do you have battery voltage at the blower motor and ground continuity when the problem occurs? 

If the fuse, relay, fan motor and resistor are good then there's an open circuit in the dash switch or ground. 

GS

It is going to take a bit more investigation then..... (I attached the wiring diagram from an '01 manual)

 

You will need to connect a volt meter to the hot to the blower (and reference to your own ground elsewhere) to see if your 12v positive stays available.

 

Here is the FSM of the controls.  The blower speed is referenced to ground through the switch on the dash (and based on your selection for speed.)   What could be happening is your reference to ground may be going away. 

 

G201 is in the right center support of the dash.  But if it were completely loose you should be complaining about other  things.  I think your problem is closer to your control on the dash (the connector or the multi-layer switches.) 

 

HTH

 

Hag

2001 FSM Ram 8W-42-4.pdf

Hagger,  What do you mean  " "reference" to ground  maybe going away" ?

 

Do You mean the on/off selector control knob of the Three Knob unit on the dash is bad?

 

Do You just mean the ground wire?

 

So are you saying its probably the Three Knob Control on the dash ?

The Three knob control a complete unit, I can get new at rock auto

 

 

When you look at the schematic, you will see that the 12v source is basically constantly provided to the blower.  (the power runs through fuses and the relay, but the relay closes the path when the ignition is in the "run" position.

 

So 12v positive in reference to the battery negative directly should always be "hot" or "on"

 

The controls on the dash in combination with the resistors change the relationship of this 12v+ with reference to ground.  (by adding resistance to ground, the motor "sees" less true voltage than 12v. ) 

 

So the trick is to get your mind around, there will always be 12v+ available.  It is the ground reference (how the blower motor "sees" the ground) that is most likely your problem. 

 

You are going to have to do two different checks to see where your problem lies. 

1) connect a volt meter red lead to the blower hot wire (Dark Green on the 2001) and use the chassis as your ground. (not the ground to the blower motor)  (your 12v+ should not disappear at all.)

2a)leave the volt meter positive on the dark green.  place the negative on the black tan wire to the blower motor.  (this should read 12v on high, and lower voltages on the lower speeds.  It should show up immediately with the key placed in the run position.)

2b)  alternately you can change the volt meter to "resistance" or to "ohms" and connect it between the black tan wire and chassis ground.  (there should ALWAYS be continuity to ground.  The actual resistance number should be steady and only change with speeds.....  The resistance to ground should only go to "open circuit" or "no continuity" when the mode selector is in the off position.)

 

You will want to rig this up so you can have it ready to read before you start your truck in the morning and try and catch why there is a delay in the power.

 

and sorry I am mechanical, so my electrical explanation may be a bit incorrect, but I hope you are getting the gist of it.

 

Hag

Check your plugs for heat damage. The last one I looked at the blower motor pigtail was lightly melted and contact were heat stressed. After the own replace it worked fine.