SI-board battery replacement

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

SI-board battery replacement

Post by Eselfjes »

Hi, my speedometer does not work, and i think i have to replace the SI-board batteries.
The solution I want to go for, is to buy two rechargeable AA-batteries and glue a battery holder on the back side of the cluster.
But, which points should I solder the two wires from the battery holder to? Can I pry the batteries of the pins, and use cable shoes on the pins from the old batteries?
Thanks in advance :D
ImageUntitled by Willy Saxhaug, on Flickr
Blue Shadow
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Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

Remove those future leakers that will destroy your board and solder the wires to the connection points for the battery tabs.
Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

Re: SI-board battery replacement

Post by Eselfjes »

Blue Shadow wrote:Remove those future leakers that will destroy your board and solder the wires to the connection points for the battery tabs.
Hi, that is the plan :) But I am a bit confused, since it is 4 soldering points on the board, but the battery holder is wired in serial, so it has two cables. Which soldering points should i use?
Blue Shadow
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Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

Flip it over and connect to what is the + connection out of the battery stack and to the - out of the battery stack. Some of the taps don't have traces or would be the same traces as the other connections. Shoot the other side and I'm sure someone can point out the spots to connect the remote battery.
demetk
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Location: CT, USA

Re: SI-board battery replacement

Post by demetk »

That's right. Pretty sure the connection points are the ones next to that relay in your pic. The ones on the other end don't matter.
Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

Re: SI-board battery replacement

Post by Eselfjes »

https://flic.kr/p/WK1RSq
Is this the right way to do it?
Blue Shadow
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Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

don't have a board in front of me and can't see the back of yours but since the other end of the batteries are connected to each other, those arrows are the locations of the voltage from the batteries.
Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

Re: SI-board battery replacement

Post by Eselfjes »

I wired it like I showed in the last picture, but the speedometer still won't work. The three red SI-lights are lit, just like before I changed the batteries. Now i dont know what to do. Maybe it is best to buy another cluster and change the batteries?
I really appreciate the help :)
Blue Shadow
Posts: 9540
Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

The three red lights mean the SII needs to be reset.

I haven't had any indication that the speedometer (speed indication) was affected by the SII batteries. If the odometer (kilometers/miles indicator) is not working then that is probably the gears.

If you have a bad speedometer, it could be the sender on the differential, wiring to the gauge cluster or the circuit in the cluster to the speedo as well as the speedo.

And of course, you used fully charged batteries to install in the cluster remote battery holder, right? Car doesn't want to charge em just keep em charged, in general.
demetk
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Re: SI-board battery replacement

Post by demetk »

Throw some AA alkaline batteries in there and check again.
Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

Re: SI-board battery replacement

Post by Eselfjes »

Blue Shadow wrote:The three red lights mean the SII needs to be reset.

I haven't had any indication that the speedometer (speed indication) was affected by the SII batteries. If the odometer (kilometers/miles indicator) is not working then that is probably the gears.

If you have a bad speedometer, it could be the sender on the differential, wiring to the gauge cluster or the circuit in the cluster to the speedo as well as the speedo.

And of course, you used fully charged batteries to install in the cluster remote battery holder, right? Car doesn't want to charge em just keep em charged, in general.
Can the problem be solved just by resetting the SII? Nevertheless I should probably get around to doing it.
The sender in the differential has just been replaced by the previous owner. He said the speedometer startet working after the change, but it stopped working after a few meters.
I'll try to change to alkaline batteries and I was thinking of checking the circuits in the speedometer for consistency, and replace the circuits with small cables if a circuit is broken.
Blue Shadow
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Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

Those batteries are being recharged so you don't want to use any that shouldn't be recharged. One time I changed batteries I needed the peake reset tool to get my SII to return to proper operation/green lights. All other times (i've had the car 31 years) the normal shade tree method has worked.
Eselfjes
Posts: 92
Joined: Aug 01, 2017 7:50 AM
Location: Norway

Re: SI-board battery replacement

Post by Eselfjes »

Thank you for the help Blue Shadow and demetk. It turns out that the speed signal circuit on the SI-board was broken. It wasn't easy to spot, but I managed to narrow it down with a multimeter and then I soldered in an external wire. And BAM, the speedometer noe works!
Blue Shadow
Posts: 9540
Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: SI-board battery replacement

Post by Blue Shadow »

Electronic troubleshooting, glad you got it done and you have new SII batteries too.
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