I installed an '86 AFM in my '84 for comparison.

On the LM-1 air fuel gauge, the '84 fluctuates from .98 lambda to 1.02 lambda.

The '86 fluctuates from .97 to 1.03 lambda. Both will work fine, and both pass California emissions regs. I would consider them interchangable.

I agree the voltage test is the conclusive test, not resistance. If you graph the voltage output with angle of deflection, you should get a smooth curve.

 

Just a word of mention as to my experiences re: AFM resistance testing. I remember a thread (good while back) where a Gent was worrying about these abrupt resistance readings while sweeping the pot's arm,....ultimately making use of a DMM that exhibits these "anomalies" as it "range-changes".....far be this from a worn (resistive) trace problems on the board......in any case, ...I use an old school VTM (yes, I'm a tube freak),..completely analog,..with great long needle sweep,..easily demonstrating any "quirks", as she moves through her range......I dig the "revealing" movement.

I don't recall whether we actually moved the arm position or not.....(getting old, I guess?),..but CLEARLY burnished and cleaned both wiper tip and board foil...made things a "bit" better, long ago. Being in electronics, I opened this box up within 3 months of ownership,..just for the sole purpose of look/see and thorougly cleaning it,...I'm a big fan of fresh copper.......even other metals.

Good threads (about) on moving the wiper position so that it contacts a fresh path of copper as it sweeps through it's "responsibilities".....BUT NEVER touching (adjusting) the spring......

I would imagine that the resistance test would follow the same curve.....bet I'd see the return losses on the network analyzers to show coincidence with voltage curves.....I would look to Loren (or other experts in this field) to chime in on what the processor is looking at (I would assume it to be voltage). This would be dependent upon the encountered resistance....(unfortunately, large ones,....wouldn't this cause an issue?...the dreaded "null"....?

I do understand (Rusnak) that some current anomalies can occur dependent upon component device health...

and , yes, a static resistance check would be a bit different than under "load" (i.e., the betterness of voltage,..as you stated, Rusnak).

Easy-peezy: gotta' have nice contact on that wiper arm and proper cleanliness/health on the bottom side....as to copper conductivity, good to go,..as she'll give you the proper resistances,..at the proper times (smoothness)...

Otherwise, I defer to the experts....as to the "other" areas of impact (within the AFM).

Best!

Doyle

 

I need to start looking at my Lambda, too.

DS

 

Rusnak,..I should say that I don't think I've seen these "curves" (maybe so, but don't recall),..so ,..I've NO first hand knowledge nor experiences in these reading comparatives........but look to your posts....

 

I'm gettin old too, since I can't find the websites that had the graphs.

I remember angle of deflection and voltage graphs on the afm somewhere, and yes imo the simulation of load is superior. It's pretty easy to use a 9volt battery to bench test the afm, and what's even better is that the afm does not need to be opened up.

My opinion is that the best fix is to find a new or barely used afm, rather than to bend the arm. These things go a LONG LONG time before they wear out, but once they do, there is so much wear everywhere that you might as well get a fresh track, wiper, spring, etc in the process.

 

That track is quite "wide",..with much "opportunity"......I didn't mess with wiper bending (that is indicative of a problem),..BUT fresh copper trace abounds!