Hi everybody, I'd like to get some advice on troubleshooting my instrument cluster. I have the original cluster that came with the car, which I will refer to as the VDO cluster, and I bought a temporary cluster to use while I sent this one to get refurbished by Bavarian Restorations, which I will refer to as the Motronic cluster.
The VDO cluster since I bought the car has never had the tachometer or fuel economy gauge work. The fuel gauge is fine, the temp gauge works but jumps around and sometimes you have to tap it. The speedo stopped working after a diff replacement, I had a separate thread here and that problem is still unresolved but possibly/probably not related to the cluster itself (https://www.r3vlimited.com/board/for...f-carrier-swap).
The Motronic cluster I purchased on eBay had essentially nothing working when I plugged it in. The fuel gauge read full even though I had a half tank, and the temp gauge stayed on cold even with the engine warmed up. Figuring the SI board batteries were probably dead on this cluster, I opened up both clusters. I found on the Motronic SI board the batteries were indeed dead, both registering 0.7V. I found to my surprise that the SI board in my VDO original cluster were restored by Bavarian Restorations in 2016 prior to my ownership, and both the batteries came in at exactly 3V as they should. So I set the Motronic SI board aside and plugged in the VDO SI board into the Motronic cluster and put it in the car. The results of this confused me, the fuel gauge still does not work and shows a full tank, now the temp gauge shows full hot, and the tach and econometer gauge started working. Speedo still doesn't work.
Since I can't use the cluster in this state at all to send one off for refurb, (I absolutely need a working temp gauge, and I also need either a working odometer or a working fuel gauge to determine when to fill up), I'm thinking I should maybe just send this one back and start over. I am about to start driving a lot more again and really don't like driving around without a working odometer.
Can anybody tell me if the SI boards are compatible across manufacturers? They look identical to me. The VDO unit is in MPH from a US '89 E30, the Motronic is a Canadian spec that has a manufacturer date in '91. Any advice for troubleshooting any of these would be helpful.
The VDO cluster since I bought the car has never had the tachometer or fuel economy gauge work. The fuel gauge is fine, the temp gauge works but jumps around and sometimes you have to tap it. The speedo stopped working after a diff replacement, I had a separate thread here and that problem is still unresolved but possibly/probably not related to the cluster itself (https://www.r3vlimited.com/board/for...f-carrier-swap).
The Motronic cluster I purchased on eBay had essentially nothing working when I plugged it in. The fuel gauge read full even though I had a half tank, and the temp gauge stayed on cold even with the engine warmed up. Figuring the SI board batteries were probably dead on this cluster, I opened up both clusters. I found on the Motronic SI board the batteries were indeed dead, both registering 0.7V. I found to my surprise that the SI board in my VDO original cluster were restored by Bavarian Restorations in 2016 prior to my ownership, and both the batteries came in at exactly 3V as they should. So I set the Motronic SI board aside and plugged in the VDO SI board into the Motronic cluster and put it in the car. The results of this confused me, the fuel gauge still does not work and shows a full tank, now the temp gauge shows full hot, and the tach and econometer gauge started working. Speedo still doesn't work.
Since I can't use the cluster in this state at all to send one off for refurb, (I absolutely need a working temp gauge, and I also need either a working odometer or a working fuel gauge to determine when to fill up), I'm thinking I should maybe just send this one back and start over. I am about to start driving a lot more again and really don't like driving around without a working odometer.
Can anybody tell me if the SI boards are compatible across manufacturers? They look identical to me. The VDO unit is in MPH from a US '89 E30, the Motronic is a Canadian spec that has a manufacturer date in '91. Any advice for troubleshooting any of these would be helpful.
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