Ethre

Testing the resistances on my two air flow sensors (928.606.121.02 - used on 80-82 L-Jet cars, and maybe on some 16v LH-Jet cars) as indicated in WSM 24-20. Basically this indicates the ranges for resistance readings as measured across the connections on the sensor. I noticed that 4 of the 5 resistances were within range for both of my sensors.

However, measuring between connections 27 and 6 (to the temperature sensor) at 60 F though, gave me 2.83 kOhm on the one, and 2.79kOhm on the other. The WSM indicates that they're supposed to hit 4-6 kOhms at 68F (20C) though. Since the resistance goes down as temperature rises, this is not the most promising.

Can anyone confirm the WSM numbers for the temperature sensor?
It seems a little odd that both my air flow sensors would have temperature sensors fail to the same degree. Also, both the early sensors and the 944 sensors are supposed to hit 2-3 kOhm (so these two would be within range).

IcemanG17

There are 2 scales of L jet AFM's................ All the readings are different...but specifically the temp I sensor..... I don't have the exact readings in front of me....but its an easy search to find.....

another note....when the temp I sensor went down on my 84 L jet (same thing) it WOULD NOT RUN....it was about 50% out of spec....the L jet system is VERY sensitive to air temp changes....I recall higher temp (lower resistance) is leaner....mine failed lean....so lean it wouldn't run even at idle....a simple AFM swap went from non running to perfect running....

Ethre

Right - post 042 and pre 042. I was guessing that the changeover also coincides with the switch to 928.606.121.02 from 928.606.121.01 (model year 80 to model year 81). I had the same problem Hacker did though (finding the manufacturing stamp). Both meters test similarly though, and are within the 042 specs (except temperature).

Since I don't have a problem starting or running, your experience would indicate that the temperature sensors are both within spec. It seems odd to me that they both test so differently from the workshop manual range though.

Thanks for the heads up about your experience with the temp sensor failing.

Edit: I think I might try replicating the 944 guys' resistance testing.

qdac

I have 2 AFMs that both test good under the post-042 specs with the exception of Temp I which reads low on both (about 3K ohms at 68 degrees on both.)

I am considering getting a rebuilt unit to see if it helps with issues that I have on warm start (stumbles for about 30 seconds) and with running rich. However, it is kind of a pricey guess.

I would really appreciate having more than one data point for this sensor, so that I could take readings at multiple temperatures.

Ethre

That makes 3 meters testing similarily on the temp sensor. It seems rather odd to me that they would all fail so similarily - perhaps there's a misprint in the manual?

I reinstalled mine this afternoon, but can easily throw my spare in the freezer if you'd be interested in comparing a colder temperature. We'll see if I get a chance to play with the resistance readings.

qdac

I believe that the Temp I sensor values that are listed in the WSM may not be correct. There is a Technical Bulletin (Model 928, Group 24, Number 83-02 date March 15, 1983) that gives a more comprehensive set of AFM testing values than is found in the WSM.

The Technical Bulletin states that the Temp I sensor values should be the SAME between the pre- and post- 042 date code modules.

In addition, the Technical Bulletin gives Temp I sensor values for two temperatures:

20C (68F): 2 to 3 k ohms
30C (83F): 1.2 to 2.4 k ohms

There is a note that the pre- 042 values for the other tests are exactly half that for the post- 042 units. The WSM values here are consistent with those stated in the Technical Bulletin. (I'll bet that the WSM editor multiplied ALL of the earlier values by two - this is correct for all but Temp I.)

I got the Technical Bulletin from the Jim Morehouse CD set.

I have never been able to locate either the mythical date code stamp *or* any photo thereof.

Note that there is an AFM re-conditioning procedure that is described at http://www.the944.com/afm.htm. This won't help Temp I issues, however.

Turns out that I didn't need to replace my AFM after all. Bummer!