Prologue : A dear friend who owns a K10 WagonR with company fitted CNG wanted to fit a tacho in his ride from the day he bought it.
We finally managed the feat recently after 2 years and 40K kms on the odo. No it does not takes that long to execute, its just that we are a lot of lazy bums.
He is very satisfied with the end result and we thought of posting the DIY for other K10 wagonR owners on the forums. A teaser pic below
Following is the design brief formulated.
- No cutting of wires to keep the warranty intact
- Mod should be completely reversible - no drilling in dash
- Should look as stock as possible - no performance gauges
For above A-Star ZXi tacho was identified as we thought it would be easier to install due to the same engine. An order for same was put through the MASS he gets his car services from.
In meantime an exhaustive internet research was done on the topic (including TBHP) and we concluded that there is no documentation of tacho install on K10 engine. There are some excellent threads available on tacho install on old F10D engine and after burning a lot of midnight oil we arrived on the conclusion that a brown wire is available in the meter console which is the tacho feed from ECM and colour is standard through all maruti cars more or less. A separate power feed has to be provided for back-lighting.
The Plan 1 : We hoped to open up the meter cosole and tap the much talked about holy brown wire (assuming maruti must be using same wiring harness for VXI and LXI models) and install the tacho. The center deck for placing God Idol on the dashboard was identified as the preferred tacho placement. This plastic plate is easily detachable from the dash and can be easily replaced if we feel like reversing the mod.
The Execution 1 : As soon as we got the tacho we stripped down the dashboard and removed the meter console. Of-course the plan never gets executed the way it is supposed to. There was no brown wire in the meter wiring harness to be found. By now pretty frustrated we decided to stress test the meter with all the wires coming to meter console, just incase maruti got bored with colour brown. We tested the tacho with all wires atleast five times, the needle jumped on some while went all the way to full on some but none responded to the throttle input. After scratching our heads a lot decided to bolt everything back.
The Plan 2 : After being denied what we thought would be a simple DIY, we decided to get it done from our MASS as we were already invested in the tacho. On the following weekend we raided the MASS and after shuttling between service floor and accessory shop (both maintained that it was in other guys purview) we ambushed the service manager in charge in his cabin. The SM incharge is an ex-servicemen and a thorough gentlemen. He also from past experiences, by now know that we are a set of anal customers and should always be dealt with caution.
Me : we want to get A-Star tacho installed in our WagonR
SM : I regret we cannot do any-kind of modification
Me : But it is a maruti part only and VXi anyways has a tacho
SM : We are sorry and why do you need tacho anyway
This went on a full half an hour with neither of us relenting.
The plan 2A :
Me : OK, than we want to place an order for service manuals of wangonR K10. We will figure out the wiring ourselves
SM : I regret but the service manuals are only for authorised personals
Me : But the service manuals have a part number so they must be orderable
SM : Yes but these can only be ordered by service stations
above again went on for another half and hour and by now the poor SM was eyeing the door thinking of rabbiting from the torture.
The plan 2B :
Me : OK, than let us peruse your service manuals here in the workshop only
SM : OK, but only for 15 minutes, it is very technical and you will not understand anything.
In hindsight I think he would have agreed to part with his kidneys as well had I asked just to escape from that room by that time.
So here we were, me and my friend flipping through the 'very technical' service manuals within our 15 mins timeline. The feeling was funnily very similar to the last minute revision before examination we used to do in school and I was strangely feeling nervous as well.
Anyway it was quickly established that wiring harness of wagonR Lxi CNG is different from wagonR LXi and VXi. On further exploration we found the ECM diagram and found the tacho feed which was 'BROWN' only though it was meant for PS module. My friend ducked under the table and quickly clicked pics of all relevant pages. All the while I was sweating profusely with my hands shivering slightly trying to look normal. Strangely I have never felt nervous while cheating in the school examinations, I must be out of practice I guess. We also found the diagram of PS module which confirmed that the brown wire does comes upto there. By now our 15 minute timelines had extended 4 times (Service manual is a huge book and there are four volumes to it) but the SM was avoiding eye contact with us and pretending to be on a phone call outside his cabin and did not dare confront us. We called him and thanked him many times for the help extended. He looked rather relieved to see us depart.
Below is the ECM layout with detailed description that we sneakingly managed to click.
Finally the much sought after brown wire
I must mentioned here that Maruti rocks when it comes to customer satisfaction. The way SM went out of his way to satisfy two retarded customers is highly appreciated. The Testing 2B : Back home with newly imparted wisdom we tracked the brown wire under the hood in ECM. The connections to the ECM are very tight and it is impossible to take feed without splicing wire. We decided against playing with 30-40k worth of equipment and retired inside car to locate the PS module which is right below the steering column. Plugged out the connector and connected the tacho and finally it moved for the first time since acquisition and responded to throttle input. We were exhilarated with our triumph and though it was already 8 in the evening we decided to work through the night and complete the installation.
This covers the homework done before actual install. Next part shall cover actual installation.
cheers
Vishwas