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Date:         Sun, 4 Nov 2001 20:03:18 -0800
Reply-To:     Laurence Smith <smithlau@ATTCANADA.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Laurence Smith <smithlau@ATTCANADA.CA>
Subject:      Re: AFM wierdness
In-Reply-To:  <Pine.LNX.4.33.0111030943161.2177-100000@sierra.localdomain>
Content-Type: text/plain; charset="iso-8859-1"

I have found that the AFM resistence is supposed to fluctuate all over the place. It seems to go up to about 1400 ohms and then down to about 900 - certainly it is not a monotonic increase or even a smooth curve. Several messages in the archives confirm this. Evidently there is more sophisticated equipment needed to know more.

Does the new AFM work okay with the wiring connected?

Have you checked your throttle switch?

Laurence Smith Hamilton, ON 90 Westy (Fanumbos)

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf Of Blake Thornton Sent: Saturday, November 03, 2001 8:53 AM To: vanagon@GERRY.VANAGON.COM Subject: AFM wierdness

I have an 84 Westy and I took my AFM meter apart yesterday in the hopes of stopping the problem I've been having. What's been happening is that I lose all power suddenly, and almost as suddenly (sometimes) I get back the power. The van doesn't die, but it does absolutely nothing when I move the throttle.

So, I took looked at all the wires (and they looked ok) and then took out the AFM and tested it per Bentley. I also have another AFM (new AFM from here on out) thats been sitting around for a couple years that I compared to my old one.

In the resistance test, Bentley says to expect between 500-1000 ohms. Old AFM was at about 550 and new AFM was at about 750.

In the other test, you just hook up the ohm meter and move the wiper. The numbers seemed different as well. And, it also seemed for both AFM's, the resistance was not strictly increasing or decreasing. The ohms bounced around going up sometime and going down sometimes. it was wierd.

I also took the lid off the old AFM and everything looked fine inside. There was not a lot of carbon build up. I haven't taken apart an AFM before so I can't say if it was super clean, but it looked ok. I was a bit upset that I hadn't found the problem there.

So, I put the new AFM in my van and left the old AFM on a shelf. When putting it in my van, I tried an experiment. I tried running the van without the AFM connected electronically. The van ran a bit rough but it responded to the throttle. I thought this was odd as I had expected the van to not run at all without being hooked up to the AFM. I suppose the ECU adjusted the fuel mix according the O2 sensor? In any case, I decided that this showed that my problem is probably not an electrical connection between AFM and ecu (because when it happens to me, I get no response from the throttle).

Any comments or thoughts?

thanks, blake 84 Westy SLC UT


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