Hi all, I recently scored a 98.5-2001 Police Package Gauge Cluster that came out of a 98 police jeep. The only problem (obviously) is that the odometer reading is incorrect. My 99 XJ currently has 115K on the odo, but the police odo has 88K on it. This question has come up here before, and like always, the answer is either to take it to a speedo shop and bend over, or deal with the different mileage. I need some help from the electrical engineers out there to figure a way to recalibrate it. I know it can be done, but it appears to be complicated. I tore the cluster apart down to the two circuit boards. This is what I found out.
There are 11 basic IC’s on the main board (see picture). There is one oscillator on the board and it reads 4.00000. So I assume that is a 4.0Mhz clock oscillator, meaning that all data entry into the ICs are synchronous. It appears that all chips are CMOS chips. I am almost 100% sure that IC’s 1,2, 10, and 11 are stepper motor drivers, and have no effect on the odometer reading. IC5 is a buffer, and IC6 is a Schmidt trigger. IC9 is a quad NOR gate. I have no clue what IC7 is, I couldn’t reference it on the net. It’s a Philips 4632650-1. I couldn’t find anything on IC8 either. Its an IC specifically engineered for Chrysler. It reads 94Chrysler, SC427292CFN. I’m guessing that it is the IC that allows the gauges to do their self-test. But I am aware that the cluster also times the rear defrost cycle, so maybe it has something to do with that.
Now on to IC’s 3&4. They are both 8-bit shift & latch registers. I believe this is where the odometer, and trip odometer readings may be kept. But im not sure which IC controls the trip and reg odo. Unfortunately these two IC’s are surface mount. Damnit! So could this just be a matter of clocking the chip, enabling it, and shifting in the correct odo reading?
There is another possibility. The secondary board consist of the display, one big 42 pin IC, the reset switch for the trip odo, and a couple of current limiting resistors. I can’t read what’s printed on the 42 pin IC, the display is basically sitting on top of it. I believe this IC drives the 6 7-Segment displays and is also a counter. However, they may be some chance that this 42-pin IC holds the odometer reading. If this is true, then all you have to do is remove it from the old cluster and insert into the new one. It seems to be to easy though.
Guys, I need all the help I can get here. I am basically flying blind because I have no schematics for anything. If anybody can help out, please chime in. Sorry for a very lengthy post.
Brandon
Pic1: Main PCB
Pic2: Secondary PCB
There are 11 basic IC’s on the main board (see picture). There is one oscillator on the board and it reads 4.00000. So I assume that is a 4.0Mhz clock oscillator, meaning that all data entry into the ICs are synchronous. It appears that all chips are CMOS chips. I am almost 100% sure that IC’s 1,2, 10, and 11 are stepper motor drivers, and have no effect on the odometer reading. IC5 is a buffer, and IC6 is a Schmidt trigger. IC9 is a quad NOR gate. I have no clue what IC7 is, I couldn’t reference it on the net. It’s a Philips 4632650-1. I couldn’t find anything on IC8 either. Its an IC specifically engineered for Chrysler. It reads 94Chrysler, SC427292CFN. I’m guessing that it is the IC that allows the gauges to do their self-test. But I am aware that the cluster also times the rear defrost cycle, so maybe it has something to do with that.
Now on to IC’s 3&4. They are both 8-bit shift & latch registers. I believe this is where the odometer, and trip odometer readings may be kept. But im not sure which IC controls the trip and reg odo. Unfortunately these two IC’s are surface mount. Damnit! So could this just be a matter of clocking the chip, enabling it, and shifting in the correct odo reading?
There is another possibility. The secondary board consist of the display, one big 42 pin IC, the reset switch for the trip odo, and a couple of current limiting resistors. I can’t read what’s printed on the 42 pin IC, the display is basically sitting on top of it. I believe this IC drives the 6 7-Segment displays and is also a counter. However, they may be some chance that this 42-pin IC holds the odometer reading. If this is true, then all you have to do is remove it from the old cluster and insert into the new one. It seems to be to easy though.
Guys, I need all the help I can get here. I am basically flying blind because I have no schematics for anything. If anybody can help out, please chime in. Sorry for a very lengthy post.
Brandon
Pic1: Main PCB
Pic2: Secondary PCB