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Anyone know if its possible to bench test an instrument cluster?

I picked up a cluster from the scrap yard. Wanted to power it on to check the mileage, so i've connected the two purples to 12v and the two blacks to ground. Set up a current limited supply of half an amp, and its pulling all of it and showing no signs of life.

Before i just crank up the power i wanted to check if anyones done this before and knows if it will even work? Does it need the serial comms to the BECM to actually come alive?

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I thought mileage was stored in the becm?
It's not much of a job to get your existing cluster out and swop really.

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Mileage is stored in both the cluster and the BeCM. Problem is that they talk to each other and both will take on the mileage of the highest one. So if the spare cluster has higher mileage stored in it than your BeCM, the BeCM will then store that.

The two blacks are ground and the two purples come from Fuse 1, but that is a permanent supply, there is also an ignition switched supply to it to wake it up. Ignition switched is on a Green wire on pin 1 of the connector.

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There will also be a dot on the display that shows differing in both parts.

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Gave it a lot more juice and it powered up with everything warning lamp on the entire thing lit up. That'll be why it wanted 2 amps!
No message center though. The ignition live on the green wire didn't seem to do anything at all. Looking at the diagram that seems to be airbag related somehow.

As above I don't want to stick it in and have the becm overwritten with a much higher value and I've no idea what miles are currently on it. My cars on 195k, so it seems unlikely it would be higher, but you never know 🤣

Anyone know if the becm will automatically take the reading from the cluster, or are there additional steps which will allow me to power it up in the car and see what's shown? There's something in nanocom about odometer sync?

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The ignition switched supply comes from fuse 23 which also powers the airbag system so it should wake it up.

The odo sync in the Nanocom forces them to be the same but if you swap another one in, you will get an Odo Error on the message centre every time you start the car.

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I know Faultmate has a manual "instrument odometer synchonise" setting under .... BECM .. other (for version 1.29). Nanocom should be similiar.

I have swapped a few BECM's in the past and the mileage was not automatically updated on mine. I did however unlock the BECM's which allowed me to enter anything I wanted.

Did you know you can take the memory chip out of an old instrument panel that you don't want (I have the exact chip no. written down somewhere). Then put the panel back in temporarily without the chip and the mileage in the BECM will go to zero. I think it still has to be synced to do this. Finally swap the instrument panel again for another new one with the correct mileage and resyncronise it again.

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yeah i think that ignition live is just for the airbag warning lights or something. Nothing happened at all when 12v was applied there.

Thanks dave3d, I had read that you can blank out the BECM by removing the eeprom and plugging the cluster in, so i guess its recoverable if i do end up with a higher mileage. I guess i just go for it?

I'll wait until i've finished the stereo bits (and now HVAC bits) first though, i always seem to start about 5 jobs and then they never get finished.

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Gilbertd wrote:

The ignition switched supply comes from fuse 23 which also powers the airbag system so it should wake it up.

The odo sync in the Nanocom forces them to be the same but if you swap another one in, you will get an Odo Error on the message centre every time you start the car.

Just to confirm, are you saying if i swap, i'll get odo error until i do the sync? Or forever more?

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You'll get the odo error until you do the sync. I have a feeling that you can put a different cluster in but if you don't drive the car, you can put your original back. I think you get the odo error then but if you sync them they are back as they should be.

One of the FETS that drive the warning lights on my cluster died a few years ago so not all of them worked. I could put up without the seatbelt warning light but when the oil pressure warning stopped working I figured I needed to do something about it. I got a replacement cluster and plugged it in to confirm all warning lights worked, then swapped the main PCB over so I kept my original clocks and message centre. Mileage on the odo didn't change but as the BeCM only keeps track of it to the nearest 100 miles, it didn't exactly match that stored in the message centre board. Doing an odo sync caused me to lose about 20 miles on the odo.