10%= new airflow meter? - Page 4 - PeachParts Mercedes-Benz Forum

brewtoo · #46 12-29-2003, 05:38 PM

Well, two things.

First, to measure the EHA mA you have to put your meter in series with on of the leads. You can take the connector apart, remove the two leads, plug the front one onto the EHA pin and place one probe on the other pin of the EHA and the other probe on the remaining lead that did plug in to the EHA.

You can't measure it by simply putting the probes in the connector.

Does that make sense??

And be careful not to short anything out doing it that way (without the MB test leads).

Also, in my experience, that sears meter won't work when measuring the EHA current but I have another meter that does work. The sears meter does not seem to let the current pass through.

fahrgewehr2 · #47 12-29-2003, 06:38 PM

Ok. Here is another illustration of my set up. I took this picture from this thread: http://www.peachparts.com/shopforum/showthread.php?threadid=62226&perpage=15&highlight=eha%20test%20harness&pagenumber=2

mhingram · #48 12-29-2003, 06:49 PM

steve is dead on the sears meter is the problem i had to use an old analog to get a good eha reading.
m

brewtoo · #49 12-29-2003, 06:50 PM

Ahhh....so you're using the adapter.

The problem is probably that Sears meter then.

fahrgewehr2 · #50 12-29-2003, 07:00 PM

Quote:

Ahhh....so you're using the adapter.

Yes.

Quote:

steve is dead on the sears meter is the problem i had to use an old analog to get a good eha reading.

Let me go check this with an older meter.

fahrgewehr2 · #51 12-29-2003, 07:27 PM

Ok, using my same setup, I get this from the EHA, KOEO:

fahrgewehr2 · #52 12-29-2003, 07:32 PM

..And here is what I see at idle, cold- BTW- This thing is getting REALLY hard to start

Am I going in the right direction?

Thanks a lot guys. Mike

mhingram · #53 12-29-2003, 07:50 PM

Mike, If I remember correctly it should be 25ma koeo and fluctuating around zero at idle with temp at 80 degrees. Steve?
Mike I will yank my book out in a bit about to sit for dinner.
m

mhingram · #54 12-29-2003, 07:59 PM

mike
I was wrong am attaching the image from th manual:

brewtoo · #55 12-29-2003, 10:21 PM

Quote:

Originally posted by fahrgewehr2
..And here is what I see at idle, cold- BTW- This thing is getting REALLY hard to start

Am I going in the right direction?

Thanks a lot guys. Mike

Does that idle EHA reading vary or is it fixed?

Are you still getting the 10% code at terminal 3? Did you see my post about my computer being bad? I had +2mA fixed at the EHA anytime terminal 3 was reporting 10%. Except at full throttle or decel cutoff...then it would be about +5mA.

I determined that my computer was bad by substituting one from another car. Then, I opened up my computer and resoldered the connections on the board. It worked perfectly after that. For about thirty minutes. Then it went back into its 10% coma and never came out of it.

Replaced the computer and fixed most of my problems. Everything is normal now (after I blip the throttle once after first cold start of the day). I think the death of my computer was coincidental and had nothing to do with my long-standing decel shutoff problem that I've complained about for three years.

I'm hoping the new pot will finally cure that.

Good luck!

fahrgewehr2 · #56 12-29-2003, 11:44 PM

1. the number is fixed

2. Always get 10% at pin 3, except KOEO. Sometimes I will see 10% KOEO, but its only after the car has been driven for a while.

Martin- thanks for the chart. I have copied down the values.

Brew- yes i did see your results with the ECU swap. I meant to reply to that...What did you pay for a new ECU? Hard to swap? not much info in the archives here. Looks like I will be tracking one down tomorrow. Used, of course.
By the way- if you read through the manual, there is some info on the decel switch.

Ok, time for bed. I will continue this tomorrow evening.

Thanks again for everyone's help. I would be lost without it. Mike

brewtoo · #57 12-30-2003, 09:14 AM

My 10% reading at KOEO was fixed. However, at idle it varied. If yours is fixed at idle I would assume it's a legitimate error code. Perhaps your pot is the problem and not the ECM.

I believe you have a pot on the way so I'd try that first.

Ain't this fun??

fahrgewehr2 · #58 12-30-2003, 10:46 PM

Pulled the potentiometer tonight. Looks new still. When comparing it to the new one, which arrived in the mail today, it is almost the same sondition wise. Im not even sure a photo will show the tiny bit of wear on the old one. I guess I'll go ahead and put the new one in, unless I hear otherwise.

To reinstall, I just line up the casing with the marks I etched into the airflow meter body, correct?

Mike

brewtoo · #59 12-30-2003, 10:55 PM

Quote:

Originally posted by fahrgewehr2
To reinstall, I just line up the casing with the marks I etched into the airflow meter body, correct?

I'm sure someone will correct me if I'm wrong, but I believe the ultimate goal is to have .7 (+-.25) volts between pins 1 & 2 on the pot at idle.

Line up the new pot with your scribed lines from the old pot. Leave the screws loose enough to rotate it to achieve the value above. Tighten it up.

Hey, how did you get your new pot already? Didn't we order them on the same day? Wonder where mine is...