Dash blower only works on high

[Hobbes]

Hi All,

My dash AC/Vent/Heat only works when the switch is on High.  Anyone know where the resistor block is located on Winnebagos of my vintage?

Thanks,
Dan

[Rickf1985]

Outside on the heater box on the passenger side. right on the face of the box.

[Hobbes]

Thanks Rick.

I found it, tested it to confirm it was bad, got a new one from NAPA, installed it, and all is working great now.

For reference, the NAPA part number is BR308.

[ErikTande]

I think I'm having a similar issue.   I really don't get any air out of the vents unless I put the fan on high, at which point the blower on the passenger side gets insanely loud, and i still don't have a lot of air movement.

How do I test my resistor block?  Anything else I should look for?

[CapnDirk]

My resister block (which seems to be a common one for heater fans)  has 3 wires in, and one to the fan.  Each of the 3 wires in hits a place on the resistor that has more resistance  before going to the fan.  The more resistance, the slower the fan.  The usual failure is the resistor breaking at somewhere along its path.


A voltmeter set to Ohms resistance should show you resistance between the many wires going in (check one at a time), and the one out to the fan.  If you get nothing on one or more of the incoming lines your resistor is likely bad.


Dave in recent months posted a pic of the layout.

[ErikTande]

Here's a video of my issue, blower doesn't work at all and only makes noise on high.

The resistor that Hobbes posted ( NAPA BR308) might be my issue.  It's not connected to anything, should it be?

and if you pause the video just right at :49-:50 you can see a little wire loop that looks like it should be connected to the little solonoid on the heater hose to the left of it.  Should it be connected there?

https://youtu.be/s867ToeQp6A

Thanks!

[Rickf1985]

Well, a picture is worth a thousand words! That "thing" hanging out under the hood is the blower resister. It is "supposed" to be mounted in that blower housing on the upper left under the hood there. But it looks like you have at least two issues going on here. One is the blower switch and the other is the fact that the vent controls are not working. They are vacuum controlled. This is usually as simple as one vacuum line off. You just need to find it. Under the hood there should be at least one and probably two round ball looking reservoirs with a vacuum line in and out of each. One will be the reservoir for the heater controls and the other will be for the cruise control. You may only have one and if you do it is for the heater controls. Make sure you have vacuum going to it and out of it. If you do then you need to follow the hose that comes out up into the vehicle and be sure it is good all the way inside. Then go inside and pick up where you left off. A lot of the time there is a plug on the back of the heater control that falls or gets pulled off, this plug is a vacuum plug just like an electric plug. That vacuum issue will solve the air coming out o9f the right vents. The blower resister we will need a better picture of the housing on the far upper left under the hood to see why that resistor is not where it belongs.

[CapnDirk]

That rumble on high is the fan motor vibrating and is probably shot.  The relay part number posted looks like a proper relay.


http://www.ebay.com/itm/HVAC-Blower-Motor-Resistor-Front-Original-Eng-Mgmt-BMR18-/331759163988?epid=180427387&hash=item4d3e631a54:g:ebkAAOSwR29ZMgSA&vxp=mtr

Notice the three different coils, each providing a different amount of resistance.  Low speed on the fan goes through 3 coils, next speed through 2 coils and next speed through 3 coils.  This increases the resistance and steps down the speed on the fan. 

I had the same issue on mine, and found that high speed bypasses the resistor and supplies a full 12V to the fan, so, 2 separate power supplies on two separate circuits for the fan.

You have the same dash controller as I so I would pull it out and look for two 12V positive lines coming in first.  Rick is right in that it should be mounted to the housing where the fan is.  Resistance on those coils creates heat (works like your electric range) and is mounted in the housing so it can be cooled when the fan is blowing air into the cabin.

I would take it one thing at a time and work out the electrical problems first, then move to the diverter problems if they still exist.  I would replace that fan motor first.  That noise would drive me nuts