Heater blower not working since day one

[teahead]

Hasn't worked since we got the old girl.

It's not the switch as I replaced it and still doesn't work.

I assume the blower motor is just stuck and refuses to move.

Wonder what all I should test/diagnose before ripping the whole dash apart?

I"m trying to find out heads or tails of this diagram.  It appears that the switch, there are FIVE prongs on it, but the plug to the switch only has 3 (that I see)?  Where is the switch getting its ground?

[WRe]

Hi,
to check the blower for mobility, you can try to reach into the lower heating opening with one hand or use a suitable tool.
It still makes sense to remove the blower motor to replace the old sintered bearings with ball bearings.
See https://www.sl113.org/forums/index.php?topic=35128.msg256913#msg256913 .

The blower switch only switches 12V in 2 stages, no ground. this is directly connected to the motor.
...WRe

[teahead]

THanks.


The prongs on the switch...there are five of them.   I see the 2 going to the motor, 1 to power (fuse 6), and one to ground.  What's the other one go to?

[WRe]

Hi,
There are switches (only early versions)  with light, so one prong goes to dashboard/instrument light.
...WRe

[teahead]

Hi,
to check the blower for mobility, you can try to reach into the lower heating opening with one hand or use a suitable tool.

You're talking about on the left side in this pic, reach in that duct opening?  I tried putting in a flexible tool to put up there, but didn't seem to catch on anything.



Anyway to take off that front piece w/o having to dismantle everything?

So it looks like this?

[WRe]

Hi,
alternatively you can unscrew the right round cap (3 slotted screws) to look inside and move the blower motor. It should move very easily.
I added the early version of the switch to the description of the blower: https://www.sl113.org/wiki/Electrical/Blower
...WRe

[teahead]

I have a 1970, so my switch only has 3 wires.  I'm pretty sure they stopped putting a light on the switch by then.

"...alternatively you can unscrew the right round cap (3 slotted screws)..."

Man, sorry for being stupid, but are you referring to this on this picture?

[WRe]

No, to this, sorry! :-)
...WRe

[teahead]

ya, no way to take that off w/o taking off that big front duct, which is a royal PITA to take off.

[mnahon]

Regarding the switch: the fifth 'prong' is not an electrical connection but rather a guide pin to align the plug.

As WRe says, one of the four prongs is for the light inside the switch, assuming you have the early switch. The later switch did away with one of those prongs because it is unlighted.

Sounds like you already know the function/connection of the other 3 wires.

[WRe]

For enlightenment!
...WRe

[rwmastel]

I have a 1970, so my switch only has 3 wires.  I'm pretty sure they stopped putting a light on the switch by then.

Probably when the knob styles for dash and everything changed during the 250SL run.  I like the little light.  I think it's only purpose is to help find the knob during night driving.

Regarding the switch: the fifth 'prong' is not an electrical connection but rather a guide pin to align the plug.

I also fell for that trick when asking questions on a recent thread about windshield wiper motor connectors.