BACKYARD MECHANIC: Replace circuit board to fix wonky gauges

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This article was published 17/09/2010 (5517 days ago), so information in it may no longer be current.

QUESTION: I have a 1997 BMW 318I and the issue is with the gauge cluster. About four years ago the gauges stopped working on occasion. This quickly changed to not working more than working. At present, the gauges will click in and work every now and then. When the gauges start working, everything is correct. They may work for one minute, 10 minutes or hours, provided the vehicle is not shut off. I have been told that the issue is with the gauge cluster, but I am convinced that there must be another problem — if the cluster was gone, it should not work. The current cluster was shipped to the U.S. and rebuilt twice with no change in operation. Thank you for your assistance.

ANSWER: I’m not sure what repairs were done when the instrument cluster was shipped to the U.S. for repair, but it sounds like you have cluster problems again. There is a circuit board on the rear of the instrument cluster that operates the gauges and this circuit board has a history of causing intermittent problems, just as you describe in your car.

The circuit board can be replaced separately from the gauges, but it does involve removing the cluster to do it. There are a couple different boards used, so make sure the replacement board matches the one you have in your car before trying to change it.

QUESTION: I have been having starting problems with my Nissan X-Trail for the past couple of months now. At first I thought it was a starter problem, therefore I replaced the starter. It was working fine for a couple of weeks and then all of a sudden it just wouldn’t turn over. What would happen was it wouldn’t turn over, I would wait a bit, put it in neutral and about 50 per cent of the time it would fire. Now, that is no longer the case. I can have it starting for about 50 starts and all of a sudden it doesn’t want to fire.

I was playing with the notion that the battery isn’t getting enough power for the starter to turn the engine. Now all I need to do is boost it and it starts, no problem. It looks like the battery gets a charge and eventually runs out. I took it to a garage to check out the battery charge and the alternator performance. The mechanic said that everything was working at 100 per cent. At this point, I have no clue what it could be. I checked the connections to the battery and there was no corrosion. What do you think?

ANSWER: Because you have replaced the starter, we can rule that out. Because the vehicle starts when you boost it, I think the problem is either in the battery or with the cables. You have had the battery checked, but have it load-tested again. I have seen batteries that tested fine one time and failed the test a couple hours later. This is caused by bad internal connections inside the battery case and the only repair is to replace the battery.

Battery cables could also be at fault and I would probably check these before testing the battery. The cable may look fine but be corroded beneath the insulation. You can measure voltage drops on the cables while cranking the starter to find the problem, but the easiest way to check them at home is to use booster cables. For some reason I have never determined, the positive cables seldom seem to cause problems. The ground or negative cables and connections cause problems much more often, so use the jumper cable to connect the negative battery post to the engine block and another cable from the engine block to an unpainted spot on the body. If the vehicle starts fine, then the problem is with the negative cables or connections.

You can also test the positive cable this way but you have to be extremely careful to prevent the jumper cable from touching any ground point or you will have some big sparks and could possibly damage the battery. I prefer a visual inspection and tightening all connections. I suspect you will find a problem with the negative cable connections, and when you place the vehicle in neutral it moves the powertrain slightly, helping to make a better connection.

Jim Kerr is an experienced mechanic, instructor and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net