W108 Defrost - PeachParts Mercedes-Benz Forum

Labadie250s · #1 10-18-2009, 11:56 PM

So I turned my defroster on for the first time in my 1967 250s and it seem be reversed some how. Air is blowing out of the cowl instead of the wood trim. has anyone heard of this before?

JMela · #2 10-19-2009, 08:29 AM

Slide upper right lever and see if there's any change.

Tomguy · #3 10-19-2009, 09:12 AM

Are you saying the fan's air is "going out the in" by coming in the actual cowl outside the vehicle? If so, is it coming out strongly and are you sure it's out - use a tissue in front of the cowl to verify direction of flow. It's thrown me off many times before without doing the "Tissue trick".

Otherwise it sounds like your blower fan is failing in a way I've never heard of before.

Labadie250s · #4 10-19-2009, 06:04 PM

Yes you heard me correctly, the air is coming out of the cowl outside the car. Its strong. What does proving the direction of the air do?

280EZRider · #5 10-19-2009, 06:42 PM

It sounds like the polarity of the fan motor has been reversed. What has caused this is another matter. Has anyone been doing any "wiring repair?"

Labadie250s · #6 10-19-2009, 06:52 PM

Jmela you were right. Thanks

Labadie250s · #7 10-20-2009, 02:32 PM

Ok, so got my defroster working but now its blowing my #1 fuse. It works fine when I'm stationary but as soon as I take off 10 seconds later the fuse blows. Any thoughts gentleman?

Tomguy · #8 10-20-2009, 02:41 PM

It does sound like your polarity is reversed - as soon as air starts pushing against it in the right direction, flow causes the fan to either slow or reverse, causing an extreme amp draw and blowing your fuse. Either that or the fan is failing as I said in the oddest way ever!

Check to make sure the fan spins the right way before going further.

Labadie250s · #9 10-20-2009, 07:45 PM

Hows does one check the direction of the fan. I did the tissue trick, good idea, it worked. I'm not familiar with all the components that are involved in the heating system.

Tomguy · #10 10-20-2009, 08:21 PM

If the tissue trick shows air is flowing backwards, the fan is rotating the wrong way. Either the wires on the fan are reversed somehow or it's shot. Switch them the other way around. If the air flow is fixed, you're good to go. If not (or if the motor doesn't blow) it's some other issue.

These blower motors are $$$ - it's possible someone replaced the motor with one that "Fit" (or they made fit) but is the wrong one.