Tachometer Driver Board for 90's Mopar's

[Sailorman2005]

I have a 94 Dodge Dakota where the tachometer was failing. Upon startup the needle would float and then go full clockwise deflection, settling on the overdriven section of the meter. I pulled the old drive module from the back of the instrument cluster and began troubleshooting for bad parts and traces. I found Q2 and Q3 open on the collector side. C5 was reading 60uF vice 68 out of circuit. Not too bad for 20% tolerance. My issue is I have no datasheet on the 14 pin DIP and could not find this part anywhere online. The drive board part number is 4375410. It is a common board used in many Chrysler vehicles of the 90's. However, finding a good working one is sketchy at best. I would like some input on how I can test this board for a good input/output utilizing the ecm signal for tach. However, i do not know if this is just a 5v signal with an alternating squarewave or something else. If anyone have experience or knowledge on how to best test this circuit board I would be forever grateful. I will attach a diagram of the only schematic I could find. According to the repair manual the ecm sends a signal with the following for calibration reference.

 

[rjenkinsgb]

The CS289 tacho IC looks to have suspiciously similar pinouts!

https://cika.com/soporte/Information/Semiconductores/CIlineales/CS289.pdf

 

[rjenkinsgb]

The LM1819 seems to share the pinout - it may be one of the devices that was made with different numbers by different companies, but all interchangeable, for major car manufacturers to source from.

http://www.elektronikjk.com/elementy_czynne/IC/LM1819-3.pdf

 

[Sailorman2005]

It does look very similar and is a CS chip. I will have to do some more research to see if this would be a suitable substitute. Thank you for the information.

 

[Sailorman2005]

I did some more testing and found that the biased voltage to pin 13 from Q1 to the chip was non existent. I used a function gen to test for signal to pin 10 and that line works. I suspect my 12v line in is not powering the chip and have no signal out. When I receive some replacement parts I will perform another test.

 

[Sailorman2005]

So, an update on the circuit. I replaced Q2 and Q3 on the board and now have a good voltage at pin 13 of the 14 pin DIP. (this chip is still non-existent). I am still testing for a good tach signal out to pin 7 and will update when I have a conclusion on the functionality of this board.