1998 Instrument Cluster Board - Odometer and PRNDL Intermittent
 

I have been experiencing the intermittent odometer and shift indicator. They go in and out, can sometimes bang it to get it on, but not always. I've seen the tach go crazy once.

With inspection looming, I finally have had to pull it apart to check it out.

In the process of removing, I turned on power and was able to move the board in various places and have the devices light up.

On removal, to my disappointment all the solder joints looked good.

I put it back in and went for a drive. I had the board just sitting in its location, not screwed in. I went to press the trip button (stupid move). The board pressed and something made contact with metal, a nice wisp of smoke came out of the back of the board. Great.

Back home, take it in and flip it over - I burned up two circuit traces. No apparent component damage. Solder time. I put in two nice jumpers, put it back in the truck, board appears to be fully functioning. No problems at all with the odometer.

So I don't know what the point of failure was? It has to be a connection of some sort. Any thoughts of what to do? Just go around and touch up a bunch of joints?

Another point I'd like to ask about: The board was quite hot in the area of the voltage regulator (duh). But some resistors were particularly warm, the ones in the lower left, labeled R50, 51, and 52. These three are in parallel.

I measured 35 mA through them. This is 400 mW in each! 1.2 W running through that circuit node.

Anyone have any thoughts about this? They look like 1/2 watt resistors.

Thanks.

Been there and done that several times. Re-flow each solder joint at the main connector at the top of the board. Seems like I remember 24 joints. You will need a magnifying glass, low wattage soldering pencil, and 60/40 Lead/Tin rosin core solder.

I use a loupe for surface stuff. Works great, except I'm prone to burning my nose.

I'll go through and hit those, probably ground pins are candidates as well.