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Pelican Technical Article:

Aspirator Motor Replacement

Greg Baxter - Peach Parts

Time:

1 hour1 hr

Tab:

$96 to $115

Talent:

*

Tools:

flat screwdriver, trim removal tools

Applicable Models:

Mercedes-Benz W140 (1992-99)

Parts Required:

Replacement aspirator motor/sensor

Hot Tip:

Clean out any dust from the module before you reassemble it

Performance Gain:

Quick and accurate temp changes for the interior of your car

Complementary Modification:

Replace any burned out lamps

This is a how-to guide to fix the Aspirator Motor, aka Sampler Motor, aka Recirculation sensor, aka Ambient Temperature Sensor, aka Cabin Temperature Sensor etc. I've seen it listed with as many different descriptions, but the part# is still 140 830 00 08 for late model W-140s.

If you are having a hard time keeping the inside cabin temperature at your setting, then you may want to look at this. MB uses a similar air pump for most models since 1990 - but all models seem to be laid out a bid differently. On the W-140s and W-220s, this combination [miniature blower and temperature sensor] is located in the overhead switch cluster (sunroof, etc.). On some E class and 300s I've seen, this air pump is in the dash next to the glove box, and fed by a small hollow tube that runs from the overhead, down the windshield post and over to the sensor motor. In any event, this DIY is for W-140s.

I would not have bored you with such a simple DIY, but a motivation for writing this DIY is the surprising frequency of this part needing replacement. They seem to clog often, or just quit spinning altogether. To make matters worse, when they act up these Aspirator Motors will drive you crazy trying to keep the cabin temp at a level, specific temperature. If this little motor clogs or goes bad, the indicated inside cabin temp will be all over the place. One I replaced was showing 30deg F to 100deg F swings in about 30 seconds.

Obviously what happens is the temperature you set on the control panel will simply never occur. Instead, the system will chase whatever temp the aspirator motor is sending at the moment, with a built-in 15 second delay to prevent thrashing. This one (this actual replacement) was just sluggish - and it took about 5-10 minutes for the system to catch up and change the temp. In the meantime, I (and all other vocal people in the car) were either real hot or real cold. Problem was the Aspirator was just clogged and almost stopped, and could not pull air from the cabin to ascertain the actual temperature.

One more note before we replace this thing. If you want to see the temperature the Aspirator Blower/Sending Unit is actually sending to the system, put the display panel into diagnostic mode. Hold down "REST" for 5-6 seconds, and the very first item to be shown is cabin temp. Just press "REST" again and it goes back to normal.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Ok - here we go.
Figure 1

Ok - here we go. Here's the part we're going to be replacing - the "Aspirator Motor".

It's located in the overhead - notice the small air intake next to the sunroof switch.
Figure 2

It's located in the overhead - notice the small air intake next to the sunroof switch.

These light covers just pull down and pop out.
Figure 3

These light covers just pull down and pop out. I think you can see the notches in the other side that hold the lens covers. If you want to (and you're careful), you can actually release the plastic catches using something like a Popsicle stick or even a screwdriver. Softer the better - even though this plastic is robust compared to most MB plastics, it can still crack. Again, I just pulled them down with fingers (shown).

Both lens covers off, exposing flood lights.
Figure 4

Both lens covers off, exposing flood lights.

See those little tabs on either side on the front of the housing? Just slip a screwdriver in there and it all starts popping out.
Figure 5

See those little tabs on either side on the front of the housing? Just slip a screwdriver in there and it all starts popping out. They unlatch from the front of the car to the rear. The rear latches are fixed, so they're last as it drops down.

A better view of the latch.
Figure 6

A better view of the latch. It's really that simple.

Out it pops.
Figure 7

Out it pops.

The new one.
Figure 8

The new one. Should be part # 140 830 00 08 for W-140s.

Wires still on.
Figure 9

Wires still on. They just pull off - you can't mix them up when re-plugging as each has its own match.

Unplugged.
Figure 10

Unplugged. Old Aspirator Motor still attached. The plastic tabs that snap hold the Aspirator are underneath this whole assembly. There are 2 ways to unlatch it - 1) it's held by a base plate, which has its own set of 4 latches. They break VERY easily. Or 2) you can GENTLY twist the motor and the tabs will release and out it pops. In any case, I saw no good method to get it out by accessing the snap tabs on the motor. I just couldn't get to it.

A photo of the old motor - thoroughly clogged.
Figure 11

A photo of the old motor - thoroughly clogged. The little diode is the actual temperature sensor/thermistor, it sits on two thermal pins and runs down into the motor.

Not a good photo, but here's the new one going in to the slot.
Figure 12

Not a good photo, but here's the new one going in to the slot. You can see the tabs I was talking about earlier. Clean this whole thing out before you reassemble it - I just blew it out.

I took this photo in case you wanted to see how easy it is to replace the lamps.
Figure 13

I took this photo in case you wanted to see how easy it is to replace the lamps. The reading lamp housing just twists out and reveals yet another pea lamp.

New one just snapped into its slot.
Figure 14

New one just snapped into its slot.

These little lamps from the flood were filthy.
Figure 15

These little lamps from the flood were filthy. Same sort of grey dust that clogged the Aspirator. I just cleaned them up with a towel. I hear you can get these in a whiter color (instead of the yellowish tint) but I lost the link. If you find them post the source.

It's ready to go back in.
Figure 16

It's ready to go back in. Plug in all the wires and...

Rear in first, then snap in the front.
Figure 17

Rear in first, then snap in the front. Snap up the flood covers and that's it - you're done.

Did you notice the mirror cover was actually removed (shown in place)? I used some tack (a real tiny dab of gasket silicon) to keep it in place because it always falls out when you least expect it.
Figure 18

Did you notice the mirror cover was actually removed (shown in place)? I used some tack (a real tiny dab of gasket silicon) to keep it in place because it always falls out when you least expect it. Anyway, I'm not really sure you actually have to remove it in the first place for this simple little job.
That's it - I told you there was nothing to it! I ran a test drive after I installed a new Aspirator Blower, and the temperature lag was exactly 15 seconds behind - just like it should be. Much better than waiting 10 minutes for a temperature change (and 10 mins of bitching from your passengers) - what a difference!
See above for method to display interior temperature.

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Comments and Suggestions:
ozo ikenga Comments: Hey, I have an Old 1992 Mercedes Benz 400se, I changed the fuel pump, on cranking,It was cranking but suddenly the engine hooksno crank , i dismantled the kick and the whole was tasted ok. But still if u want to crank, the engine hooksno crank and light will go off on cluster display. what do I need to correct this situation
April 10, 2016
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 

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