Hello Folks,
I think I have an answer to the Instrument Cluster Light and fuel gauge problem on older LS400's.
If you have the common problem with the instrument lights whereby they don't come on right away when you start the car in the morning when its cold .... then its probably an electrolytic capacitor located at C212 on the small PC board on the back of your instrument cluster.
If you also have the common problem whereby your fuel gauge takes a long time to read the fuel level in your tank after starting your car in the morning and/or the reading is much lower than the true amount of gas in your tank, then its probably two electrolytic caps on the "Big" PC board on the back of your intrument cluster. One of the caps is located at C142 on the big board... and the other is located at .. C147 .
The interesting thing is that these caps are all the same style. They are very small (Low quality) electrolytic caps. They are housed in little metal cans ... with very short leads .. although they are not true surface mount caps. I tested a bunch of caps on the small board and found that only this type of capacitor was disfunctional .... and interestingly enough .... all the caps of this style were bad on both boards ... (A total of 3) ....
If you are scientifically inclined .. I need to warn you that these capacitors often do not "crap out" unless they are cold .... If you read the capacity at room temp they may or may not seem fine ... But when you put a chiller on them ... then the capacity reading starts to approach zero ...
What you should do is replace them with better quality caps .... either bipolar ... or ceramic .... or titanium ... You can go higher in voltage and also higher in UF .. it doesn't matter ... except for maybe the one located at C142 ... I am not sure .. but this one may provide some kind of timing function ... the other two are clearly just filters .... (IE: for Ripple)...
C142 (big Board) was 4.7 UF, 25V
C147 (Also on the big board) was 10 UF, 50V
C212 (Small Board) 10 UF, 16 V
Now both problems are fixed ..
LamSV was very helpful in getting me focused .... I would still be stuck without him ...
Remember .. that you need to disconnect the battery before you start removing stuff .. and wait a couple of minutes ... I made the mistake of not doing this and my Airbag warning light would not go out ... So I removed the little light bulb that warns you ... I am not sure my airbags work after 10 years .. but my guess is .. they work or not ... regardless of whether there is a bulb in the warning light circuit ...
This problem is very easy to fix for anybody comfortable around a soldering iron .. and much less expensive than having the dealer replace your boards ... (My cost was about $1 worth of parts versus $1200 if the dealer fixes it) .... the labor involved was mostly in removing than reinstalling the instrument cluster ... (About 1 hour) ... Replacing the 3 capacitors is about 45 minutes worth of work ....
Best of luck to anyone with the problem .....
Cole
