Heater Motor and Fan

[Mpgeslak]

Hi All,

I am having two issues with my heater motor and fan control.
1.  I purchased a new heater motor but it seems to rotate in the wrong direction, which is odd since there is only one way to install it due to the wiring.  The fan is rotating from top to bottom when looking at it in its installed position, and I am sure my original one rotated from bottom to top.  Can anyone confirm the direction it should rotate?  Is it possible my fan blades were backwards?  I have attached a photo of the direction mine were installed.

2.  The resistor at the back of the fan control gets very hot, so hot you cannot touch it.  I know it will get a bit hot, but this seems excessive.   The control is new, any insight on how to diagnose the problem would be appreciated.

Thanks all,

Michael

[doitwright]

The fan blades in your photo appear correct. When you lock at the assembly from the right side, the rotation should be counter clockwise.

[Mpgeslak]

Thanks Frank.  Just to confirm, from the right side you mean the passenger side in an LHD?  I took another look at my old motor and it was spinning clockwise from the right side, and it seems to me when it spins clockwise i get more of a breeze off the fan.  I feel like I want to switch the blades if it is turning counter clockwise.

Any thoughts on the resistor getting hot?

Thanks,

Michael

[Peter]

The fan blades in your photo appear correct. When you lock at the assembly from the right side, the rotation should be counter clockwise.

This is correct. When the fan it is installed, sitting in the car, looking from the right hand side it turns clockwise.
The rheostat resistor get very hot, but when you smell it. You have a problem!

Is it an original “new” motor?
If not it most probably will draw more Amps than the original. The original rheostat resistor can not cope with this and will burn.

Peter

[Mpgeslak]

Hi Peter,

Your response said it spins Clockwise, do you mean to say it should spin Counter Clockwise as Frank indicated?

The motor is from Buds Benz so not original.  No smoke, just hot, I will test the amps tomorrow.  Do you know which wire is power, I have Brown, Black and Orange (ish) wires.

Thanks for the help!

Michael

[Peter]

The motor is from Buds Benz so not original.
No smoke, just hot
Michael

Hi Michael,

I have no pictures from these repairs, so I work form memory. That is dangerous.
• Bud Benz knows their business. So  I do not expect problems a Mps. problem.
• The rheostat get very, very hot, so if do not smell or see smoke, no problem. It is made to become very hot.
• The clockwise is from memory (so maybe wrong) but you can test it. The fan position in your picture is correct. So try which rotation direction is generating most air displacement.

Peter

[WRe]

Hi,
attached the electric wiring of heating fan and switch.
...WRe

[WRe]

https://www.sl113.org/wiki/Electrical/Blower

[Sead]

The rheostat resistor get very hot,
Peter

If ceramic base is broken and needs to be glued back together, what kind of adhesive to use because of that heat???

Sead

[WRe]

Hi,
I would use a flexible (different temperatures), two-part epoxy adhesive like, e.g. 3M Scotch-Weld EC-2216 B/A.
...WRe

[Mpgeslak]

An update on the resistor:

I did the following tests with key in the accessory position:

I tested the old motor with no blades attached and it drew 1 amp, resistor stayed cool
I tested the new motor with no blades attached and it drew 2 amps, resistor stayed cool.  Motor definitely ran faster.
I tested the new motor with the blades attached and it drew 4 amps, and resistor got very hot.
Finally, I hadn’t noticed before, but with the fan control switched to the off position, the light goes off but motor still runs which I assume is a problem with the wiring

Any thoughts on what the problem can be?

All help appreciated

Michael

[Mpgeslak]

A couple of further updates:

When I run the blower at high speed the switch starts to smoke, so clearly getting too hot.  It draws about 4 amps

In terms of the fan not switching off I searched the forum and found a post that was helpful.   Looking at the resistor coil where the metal part that runs across it to change the speed comes to the end position there is a ceramic part it comes to which should stop the contact and I assume shut it off.   Problem is the metal is part on the ceramic and part on the coil and thus there is still contact and it stays on.  I read on a post that putting a little epoxy over the coil in that spot works to stop the contact and shut the fan off.   

Any insight on where the problem might lie with the smoking switch is appreciated, not sure where to go next with it!

Michael

[Peter]

Hi Michael,

I did also once some measurements on the MB motor. With fans mounted it draw 7 amp, which did not give an issue with the rheostat. So if you measure 4 amp this should not burn the  rheostat.

I got a problem with a new (not MB motor) which draw 11 amp and nearly burned (I was in time) the rheostat.

I solved the problem by using an electronic speed control, with potentiometer.
It became difficult however when I wanted the same look and feel as the original MB switch.
I rebuild the MB switch and connected in tandem the potentiometer.
A lot of work, but it works very good and the fan is now much stronger than the original one.

Peter

[Mpgeslak]

Thanks Peter.  Given mine is only drawing 4 amps not sure why I am having a problem.   Could it be the wiring?  I have looked at the wiring diagram and I have the three wires going to the blower motor, a ground and two other wires.  When I test the two non ground wires only has power going to the connector, should the other one also have power to operate the different speeds of the motor?  Sorry if it is a dumb question

[Peter]

Hi Michael,,

That is correct.
The two wire are for low and high speed. The low speed is going via the rheostat, het high speed, is going direct.
See also picture how to connect. If you change them, the rheostat will burn.
This will most probably solve your problem.

Peter

[Mpgeslak]

Thanks Peter.

In the attached wiring diagram, which of the red/green and yellow/green wires is the high and which is the low?  And does the high go to the orange or black wires that go to the motor?

Michael

[Peter]

Michael,

I agree, the diagram is not clear on this.
I suggest to make a test setup.
Same for the motor, it is easy to check which one is the high or low speed, by connecting to the 12 volt source/battery.

Peter

[Mpgeslak]

Peter,

I did the test as you said and determined the green/yellow wire is high speed and that my motor is wired correctly.  I also realised I wasn’t quite turning the switch all the way to get it to the high speed position, and when I run it on high the switch doesn’t get hot.  When I turn to variable speed it smokes.  I guess the only conclusion is the switch is bad, even though it is new?

Michael

[Peter]

Michael,

The 4 amps is low speed with fans?
If so, there should not be a problem.
My measurements where at the time with the MB motor 5,2 Amp. low speed and 7,0 high speed. 

Peter

[Mpgeslak]

Low speed is about 3.6 amps and high speed is 4.3, which I agree shouldn’t be a problem.  Not sure what else to try?

[Mpgeslak]

Is there a way to test the functioning of the switch and the rheostat?

[Peter]

Good morning Michael,

With a multimeter you can check the one/off function and the resistance of the rheostat. I assume you did this already. The Amps of the rheostat you can not measure, but you know that is around 4 Amp. the rheostat gets very hot and start to smell and smoke. This is clearly out of spec.

Peter

[Mpgeslak]

Hi Peter,

First of all, thanks for all your help.  I am a newbie on much of this and really appreciate the guidance.

I did two things this morning:
1.  I tested the resistance of the switch.   Set the OHM scale to 20, at the fully on side of the variable switch get a reading of about .8, at the slow side of the switch I get about 4.3.
2.  I carefully ran through the range of the switch with the motor connected.   At the high end of the variable switch, it doesn't get hot at all, in the middle it gets hot, at the low running speed is when it smokes.   My observation is the low running speed is very slow and I am not sure you feel much coming through the vents.

Any thoughts on these latest tests?

Michael

[Mpgeslak]

I also went back and test the amp reading to make sure I did everything right.  I think I may not have paid enough attention to where the switch was positioned and thus my previous readings didn't reflect maximum and minimum amps being drawn.  Here is what I found:

With switch in high position it draws 8 amps.   What I also found was if I disconnect the high speed wire the motor still runs which means the variable switch is not going off.   Without the high speed wire it draws about 6.5 amps.   The rheostat doesn't get hot in this position which is expected

With the switch in the highest variable speed it draws 6.5 amps and at the lowest speed about 2.25 amps.    The switch get progressively hotter through the range and smokes at the slower speeds.  In the off position the motor still runs at a slow rate.

Apologies for the earlier mis-information on the amps being drawn.  Any thoughts?

[mnahon]

Hi Michael,

The resistance checks you did are good---it should be around 4 ohms at the lowest speed setting, and approaching zero at the highest setting.

There's around 25-70 watts being dissipated in the system (2-6 amps/12 volts). At low speeds most of the dissipation is in the switch and at higher speeds, most of the dissipation is in the motor. So you would expect the switch to get hot at low speeds; but not smoking hot, unless there's something wrong with the switch.

You say the switch is new; but these switches are no longer made. Where did you buy it new?

Meyer