Potentiometer settings
 

hi gang just-n-time here,My question is the proper setting for measurement of this precious little bugger.MA.,volts, ohms? I have finished the EHA. and am still having a search problem on deceleration,and a little more roughness than
the engine should have.
I mark the position of the pot.and after making several readings in various settings,I tried to move the position of the pot and it made no difference in
the running of the engine.
I have been reviewing info fromThomH,stevebfl,patrick_mb, M.B.DOC, sborg.
Problem is that I can't get the ohm reading or the voltage nothing that even comes close to what they have had.
Removed the unit and the marks inside the unit are deep into the,what I would call resister's and if some one can explain to me how to adjust entire unit I would be thankful.jnt:D

Air meter adj.
 

Key on engine not running,top of sensor plate even with lower edge of cylindrical part of air funnel,plug installed but pulled back enough to measure voltage. Pins 1 and 3 should read about half a volt, at pins 1 and 2 read .2 to .5 volts.
Slowly push sensor plate all the way down and you should see the voltage rise continuosly to 5 volts at full travel.
Mike

Deep groves in the carbon usually means that the POT is worn out. That might explain why you cant get any good readings.

voltage test
 

Thank you Mike,for your reply. koeo and do I need to unplug the EHA? Engine fully warmed?
Wish I had the papers I threw away I had a test done like that! but as I recall as the plate went down it traveled from 3 to 9 erratically just bounced up and down then as I got close to full open it went to 5 steady.
Tomorrow Miss Debbie have to go back up to Shreveport and when I get home I will make the new test, Will report tomorrow night.jnt:rolleyes:

deep scars
 

Yes I think as much, but wish to do as much testing as possible.jnt:laugh2:

what model is your car and series?

cause I toy with the eta pot and have learned to test, use and repair it even in my sleep. I suffered that nightmare too, so was able to get all the proffesional help from the MB plant and some technical adviser from Bosch, plus due dilegent.

year & mod.
 

COOL, The car is a 420sel and a 1990. the pot ends in 035:book:

Airflow meter adjustments
 

JNT
The test I described is done with the plug connected. Readings with the plug off mean nothing! Look for a smooth transition from full closed to full open. The sensor pot is available on many sites on the web.
Mike

test 1&2, 1&3
 

Great Mike,the test will not come even close to those numbers.
KOEO 1&2= 107.2, 1&3= 4.77, 2&3= 4.67 those are neg.on pin one and on pin two to get the 2&3 reading
KOEO ground lead to air mass body,
1= 16.5
2= 123.7
3= 4.79
I have a new meter from sears and tested the duty cycle at 60.2% at idle and at 2000 the EHA is -0 to pos. 0
+.01at 2000 so all that area is in good shape.

leads to EHA!
 

I know the leads to the pot must be on but I was referring to the EHA?

setting potentiometer
 

Well the new unit arived and I took ohm readings from the old and the new,I have placed the new one on and set the voltage to .67. This has not changed the low end serch but a very slight amount, so my next question is should I reset the trimpot, so it reads the same ohm as the old unit?
old was 94.7ohm, and the new was 57.2! jnt:dizzy2:

POTENTIOMETER set.
 

Well this is the latest pot work on the 420sel, Removed the pot and re set the ohm to 94.7,from the factory setting of 57.2. This made the unit much more sensitive to alignment,The .7 was far more difficult to achieve, Though I did get it to settle at .668 to a swinging up to .701,I stopped it at that point and will test drive it for a few days just to get the real life testing done. Though I must add after several snap test it held at 700 on decel. and on three fast snaps it only fell below 700 once but no stall. will finish this up after I have tested for a couple of days.JNT:pirate:

i do not understand why you have to set the potentiometer, its suppose to learn by itself thru the control modules. the only time you need to get the reading is when the pot does not seem to respond to the control module and in that case you would need to replace it, no other way of reparing it, due to how these parts are designed and made.

Read more post!
 

Cool all I can tell you is what I have read from post's about this very subject,they are all very different and are a bit confusing,as to the setup of the pot, some have reset the pot (new) to the old some have not, I suppose since,I was able to get the .7 I probably did not have to set the ohm of the new pot to the old,but no one could get back to me so I did just that now I will see what the affect will be.JNT:eek: