124 Blower - Did I make a mistake? - PeachParts Mercedes-Benz Forum

lrg · #1 02-29-2008, 01:38 PM

I recently replaced the blower motor (motor and squirrel cage fan assembly) on my '87 124. I've noticed the volume of air through the vents isn't what I think it should be. Is the blower motor "handed"? In other words might I have put it in facing 180 degrees the wrong way?

I also need to replace all my vacuum pods at some point but as it stands now I have a sneaking feeling that since I'm not getting a lot of air volume anywhere I screwed up and put the fan in backwards. Anyone know if the fan needs to go in only one way?

I hate it when I rush these projects.

79300sdtd · #2 02-29-2008, 02:16 PM

if it is anything like the 116's they are directional but you can only install its one way. the cage scoops air from the outside and ejects it from the middle i think. to reverse it the plug would probably have to be switched (i.e. the + and - are now - and + just like an electric motor)

Is it a brand new blower or is it a used one?

lrg · #3 02-29-2008, 02:34 PM

It's a new blower and the plugs are on the wires, not attached the mounting, so I think it is possible to put it in 180% the other way. The wiring is pretty idiot proof so I don't think there's a problem with it running backwards. I agree though, the fan looks like it would work the same either way - air drawn in from the outside and I believe ejected from the ends. It's just that even on high speed it seems to make a lot of noise without much air coming out of any of the vents.

babymog · #4 02-29-2008, 03:00 PM

It's possible that you got the positive and negative backwards.

It is a dual squirrel-cage, the air is centrifuged out through the fins. If it were running backward, it would still move air, just not very efficiently and probably at higher RPM with the reduced flow.

79300sdtd · #5 02-29-2008, 03:22 PM

i would say if anything could be put on backwards it is the cage.

look at the two blowers side by side, if everything looks the same (directions of the fins is the main thing, looking into the cage from this view.. O... and the bolt in the middle) then try switching the plug so the positive and negative are switched.

lrg · #6 02-29-2008, 03:53 PM

I'm pretty sure it's not possible to put the plugs on backwards so I don't think reverse polarity is the problem. The blower came with the cages attached and the fins point the same direction. The question is if the whole fan faces the wrong direction does it matter? If this were a bladed fan it would be obvious but for a squirrel cage in a housing I'd tend to think it wouldn't matter as they suck air in all around the cage and blow it out the ends. I have a feeling I'll be taking this apart this weekend to find out.

babymog · #7 02-29-2008, 05:12 PM

Squirrel-cage blowers pull air in through the ends, and blow it out through the fins. The fins should hook toward the direction of travel, not away, as they are there to spin the air not to push it out, centrifugal force takes care of pushing the air out through the fins.

And therefore, the squirrel-cage blower's output is directional, the air comes out somewhat in the rotation direction of the blower cage. If installed backward as the OP suspects, and the housing is designed to take advantage of the directional output (it is), it will be less efficient when installed backward.

Seems there would be something to prevent this, I think the motor is offset to one side, I will check the one in my parts shelves and report back.

babymog · #8 02-29-2008, 10:42 PM

The blower motor is offset, only fits one way (tried it in a spare '87 unit in the shop).

The wires are one male / one female, difficult to reverse also.

Pretty much means that unless the motor was wired wrong, or the blower wheels installed wrong, it would be difficult to have backwards.

The blower rotates the same way as the car wheels traveling forward. The "hook" in the blower vanes should point forward on the top.

tobybul · #9 02-29-2008, 11:53 PM

I agree that the wiring and plug is set. But if I read your note correctly, the new plastic blower came separate from the electric motor. Therefore, it is possible that you may have installed the blowers to the lectric motor incorrectly. The blower blades have to face a certain way. The blades need to face towards the direction of the rotation - not away from it. As suggested above, compare it with the old ones.

lrg · #10 03-01-2008, 01:41 AM

The new blower motor came with the cages already attached so I think that's not the issue. Thanks Jeff, you've saved me needing to dig into the blower housing again as it looks like it's not possible to put the blower in 180%the wrong way due to the offset. I'm guessing that my vacuum pods have now gotten bad enough that the vent system "doors" aren't opening properly thus cutting off the airflow. I'll check that out first and go from there.

Thanks all for your input.

Randy

Bio300TDTdriver · #11 03-01-2008, 02:09 AM

When your pods fail, the default position is the defrost. Are you getting good flow through the defrost?

babymog · #12 03-01-2008, 10:16 AM

You should be able to see the floor-vent pods by removing only the wood fascia and the ACC (8 screws) to see if they move properly and help them by hand.

Also, the climate control gets a metered amount of airflow so one leaky pod can be enough to compromise the operation of all pods.

lrg · #13 03-01-2008, 08:33 PM

Yup, it would appear to be leaking pods. I pulled the glovebox liner and tested all the pods and it looks like at least two of them are gone. I'll get them all replaced and report back but it makes sense that that is the problem since my defrost does seem to work well. I guess it was wishful thinking on my part that this was a simple blower installation problem. Thanks everyone for your help.

Bio300TDTdriver · #14 03-01-2008, 08:37 PM

Are you going to do them? If so there is a good write up here somewhere.

lrg · #15 03-01-2008, 10:26 PM

I'll give it a go although it may take me a few weeks before I have the time to get to that big a project. GSXR did a great write up on this which I've copied and will use. I plan to do them all.