Scanmaster 2.1 Acting strangely all of a sudden

[Tom Kelly]

I have only had this 86 GN for a couple of months ad it is coming together nicely. Last week the scanmaster started acting funny. While cruising around, the "retard" reading stared generating random 3 digit numbers for 15-20 seconds and then settled. back to 0.0. This has happened several times since, always returning to 0.0.
This happens at normal (30-40 mph) driving.
Anyone experience similar behavior?
Thanks
Tom

 

[TurboBob]

does it get worse if you step on the brakes?

The stock ecms generate noise on the data line when the low speed fan is running, it gets worse when you step on the brakes.

you will see other data get wierd at the same time.

Bob

 

[Tom Kelly]

does it get worse if you step on the brakes?

The stock ecms generate noise on the data line when the low speed fan is running, it gets worse when you step on the brakes.

you will see other data get wierd at the same time.

Bob

Thank you for your reply. Yesterday the entire scanmaster went dark except for the 2.1 on startup. I "jiggled" he wires under the dash and it came back to life without any funny readings as did the green light for the alky kit. Sill working fine without the funny readings. Since it's working I am leaving it alone for now without looking for the loose connection. If it goes out again I will search the wiring.
Have to address a new problem. the radiator fan resistor assembly is falling apart. Lost low speed action. Patched it together but will be looking for a new resistor assembly (as if there around) or a nice clean fan complete with the wiring. Not urgent as I can always turn AC on to get the fan going if I am stuck in slow traffic.

 

[TurboBuRick]

I was seeing the same thing recently. Just random numbers on both readings. Shortly after my alternator took a crap. Since I rebuilt it I have not seen it happen. I wonder if the bad alternator was making noise in the electronics.

 

[Tom Kelly]

Well finally discovered that the problem was that the connector used to connect the source wire to the ALCM was not sized properly and was just a little bit loose, just enough to go out one in a while nd cause funny readings once in a while.