paalw

Thanks, will try this out and will get back with the result.

I agree the knowledge here is unbelievable, thanks Ian S4 for your effort!

paalw

Okay, so I got around to setting up my home "lab" My results:

When touching pin #3 (left on pic, earlier measured 76 ohms from this green to yellow lead) there is no reaction what so ever.
When touching pin #5 (right on pic, earlier measured 55 ohms from this green to yellow lead) I hear a click from the motor, and if my finger touches the "screw" i can feel it moving something like 1/100 turn or something like that when connection to the pin occurs, and when i remove the lead from the pin it goes back to starting position. It does not turn the odometer numbers at all. But there is life!

I also tested touching the solderings for the correct pins from the bottom side of the board, and from the green wires going down to the board upside, but there were no difference in behavior.

So, can anything be read out of this? Motor done?

Ian S4

I think it's time to disconnect the green wires from the board and try grounding each one in turn. Either the motor is dead, or the chip is dead, and separating them will reveal which. My suspicion is that the motor is OK and the pin #3 output-stage of the chip is fried. The motor has just six "clicks", and each pulse should rotate it by that amount.

Ian

paalw

Read my edit: Just added that i also tried to touch the green wires, there were just enough room of unisolated lead so i could touch the green leads directly just above the PCB. Same behavior. Would i still need to disconnect them to find out if it's the motor or the chip?

Regarding the motor clicks. When i turn it by hand there is a natural electric motor resistance feeling like "steps" or "clicks", and 6 clicks for each turn sounds about right according to how it feels.
But while grounding the pins, it (the one that moves at all) doesn't move nearly as much as one "hand turned" click. The movement while grounding is just possible to feel with my finger, and when i remove the grounding it feels like it lets go of the pressure and goes back to where it was.

So one might be totally dead, the other on death row.

Ian S4

Yes, if the chip output-stage is shorted or low-impedance, it will interfere with any tests you do on the motor while it's still connected.

The motor requires that the green wires are alternately grounded. That is, if we call the green wires A and B, then they need to be grounded ABABAB etc. If say A is dead, then BBBBB... will not make it move, but you will hear/feel a slight movement. Only way to be sure is to disconnect both the green wires, I'm afraid.

paalw

Thanks a lot Ian.
Will be back when i have something.

paalw

Ok - update and an end to this story.

The testing procedures that Ian provided made it clear that the chip on the circuit board did not work as it should. Ian sent me a known working spare chip he had laying around, and I swapped it onto my board once it arrived.

First test was negative - now both odo AND speedo were dead. Took the speedo out again, went over the solderings and found a suspicious area. Compared my solderings to an untouched circuit board, then soldered the missing connection i suspected. Inserted speedo again and VOILA! Everything is working.

I have heard A LOT of odo gears breaking stories in here, but never heard of this one. I hope this thread will help others if they experience the same.

Big thanks to Ian S4 for helping me out. Never would have figured this out without him.

Rgds
Paal

M. Requin

Thanks gentlemen, excellent thread for reference!

fraggle

Very timely, this thread bump! I have a winter project here.

SMTCapeCod

Nicely done- subscribed, rated.

Ian S4

I ought to add that the procedure I described above applies only to the SAY115 chip. Some cars used the UAF2115 chip, which has a different pin-out. Specifically, instead of shorting pins #3 and #5 to ground, use pins #2 and #12 instead.

Adamant1971

Thanks to all for this thread. This just helped me solve the odometer issue on Alex G's 78.

After running the tests I finally had to disconnect the wires. Sure enough once disconnected the motor works. It ticks but does not move while tapping one ground, but when I alternate between the two grounds the miles start clicking away.

So all is good with my gear repair and motor. Signal is getting to the unit since the spedo works fine.

I guess I have a dead chip (115).

Adamant1971

http://www.amsyx.com/say115y.html

If this is the correct chip, it aint cheap.

From what I read the Y is a different ratio (miles to motor clicks). The Y looks to be used in older 328's.

Anyways for giggles here is the data sheet on both chips.

todmaceachern

Why can I not see the picture? Can anybody send me the picture that was posted here? Thank you.

todmaceachern

In Post #28 of the 12V connections.