Code name: Road runner
Symptom: As refer to my previous post about my ever make best car, my SEG is running at around 140km/h at 5th gear with 3000 RPM. I hope it’s true, but I know there is something wrong with my meter.
Action: I had been asking around the spare part shop to get a new meter but none of them selling and they told me the meter is very expensive if I want to get a new one. The cheaper way is get it from car scrap. Searching around internet and forum but get none positive result. Finally talk to a mechanic and he told me that there is a PCB board behind the meter, since I’m best electronic engineer in town I plan to save my meter with all the knowledge I have.
Unscrew all the screw on my car dashboard (total got 6 screws) and unplug the cables (total three cables), the dashboard is detached from the car. Everything looks fine on the flexible plastic PCB behind the meter. So I plan to open the plastic cover of the dashboard. Two screws and compression fitting (not sure how to call that kind of connection :p). Once the cover is removed, the meter is now exposed. There are four screws at the back of the speedometer, so I unscrew it and the speedometer is detached. Looking behind the meter, there is a PCB board. No cool solder was found, no burned component, also no lose connection. Almost give up with the saving mission. Suddenly I notice a black material on the top of the meter. Using a multimeter to measure the connection between the two points. A very funny reading come out, 1.4kohms. Finally I got it.
The resistor behind the meter is 3.9kohms, and the black material is “eating” the PCB track and leaving 1.4kohms. So the additional resistance is causing my speedometer running at around 40% higher speed. 1.4/3.9 = 36%, so that the source of the problem.
Since the track can’t be repair, I just solder a small wire to replace the broken track and the mission is complete buy putting back everything to the car.
Result: No need to say too much, my SEG got it correct speed again.
i got a broken AMD sc939 mobo. can fix for me ah ?
ReplyDeleteno. you can donate to sg for land filling
ReplyDeletehahaha
ReplyDeleteWhen Ding became mechanical guy liao?
i have a door dell broken... help me to repair
no lar, i ledy donate enough used condoms to sg liao. afraid they might drown in my dried cum soon...don't want to suffer them anymore with my junks..
ReplyDeleteoi leng chai.. you better replace your meter quick..
ReplyDeletethe black substance will continue to eat the pcb until it causes cavity. I have come across this many times on frequency inverter pcbs. It is acidic in nature and originates from lead, usually during manufacturing donkeys years ago. Ultimately your pcb will have holes in it.
boss, thanks for the advice. already clean with every detergent that i can found in my house. some more put a layer of conformal coating which used for contrec meter.
ReplyDeletenot sure my millage will reset like contrec meter or not :)
the kaninabeh contrec meter not even good enough for a fuck!!
ReplyDeletegood to hear that you have solved your speedo problem...