My speedometer has an intermittent problem where it completely stops working and I've determined it's the capacitors so I'm using the FAQ as a guide to replace them (http://www.brickboard.com/FAQ/700-900/ElectricalSpeedometerRepair.htm)

for C7, C12, C6, and C16, the capacitors and/or the PCB are all marked with +/- so it is obvious how to install the replacement caps.

However for C15, there was no marking on either the capacitor or the PCB and I have no idea how to install the new one. If I guess, I'm sure I'll install it wrong and I really don't want to do this twice.

Can someone please tell me how to install capacitor C15? Thanks!!

I finally got my speedo back together, what a pain in the ass that was. Everything works now, except the reading is 9mph faster than I am actually going. The reason for this is because I ended up needing to remove the needle from the gauge, somehow one of the tiny winding wires broke off from the end of the terminal that holds the PCB to the meter and there was no way to fix that other than to pop off the needle. When I put the needle back on, I must not have put it back on in the same place. I might try again this weekend.

Anyway, the FAQ about the capacitor replacement is great, and I'm not seeing the 45mph problem that some others on the board have reported.

I ordered the 5 capacitors from mouser.com, part numbers:
UEP1HR47MDD
UVR1H6R8MDD
UVR1E470MDD
UVR1E100MDD
USR1H220MDD
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Matt L. -- Cary, NC -- 1991 740 wagon

Matt, which part number goes with which capacitor?
Steve
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See the 700/900 FAQ at the drop-down menu above right.

Matt, is this the 140mph or the 120mph speedo?
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See the 700/900 FAQ at the drop-down menu above right.

Mine is the 140mph speedo, same one as in the FAQ at the link that I posted.
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Matt L. -- Cary, NC -- 1991 740 wagon

Matt ..the numbers on the two ICs have faded on mine .If yours are legible could you tell me what they are starting with the IC thats opposite resistor eight ( R8 ) on the board and it is the one that has two indented dots ..at least on mine...thanks ...Paul

The IC closest to R8: AN6505UBK (looks like google has some hits for this one)

The other IC: (3 lines, from top to bottom)
J3
SP-ST-1
YZH 09 3

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Matt L. -- Cary, NC -- 1991 740 wagon

Thanks Matt keep in touch

Matt C15 is a bipolar cap...you need to get a bipolar cap and it can be insatlled either way. I have some pics in the personal and technical areas of the picture gallery. Also a few of us have done the cap replacement only to find out that the speedo will not go over 45mph. Pls post back after your fix and if you need any tid bits let me know..To reiterate C15 must specifically be a bipolar capacitor.Paul

Thanks so much for the quick reply. I did the disassembly today now I have to go order parts. Good thing I waited for your reply before ordering! I did not notice leakage from any of the caps like some of the pictures I have seen but I am 100% sure my problem is in the gauge and not in the sender or anywhere else. Over the past year this went from an extremely intermittent problem (once a month or less the speedo would "shut off"), now it happens multiple times per day and rarely can I drive more than 2 miles until the speedo stops working.

When I get the parts I'll let you know if I'm also seeing the 45mph problem. What are you doing to fix that?

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Matt L. -- Cary, NC -- 1991 740 wagon

Matt, can you take a look at your speedo pcb and let me know which caps have solder on both sides of the board. If you look closely at the ICs for example you will see they are soldered on both sides. Some components are not

I already removed all those caps but I don't remember whether they were soldered on both side or not! Oops! Usually those types of push-thru parts are only soldered on the back. I don't even know how to get solder on the front between the board and the cap - some of those spaces are tight!
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Matt L. -- Cary, NC -- 1991 740 wagon

Well it a project that I will revisit in the near futre as I have a replacement cluster thats working. I think I will try the ICs next, if I can source them ,then as much of the other components as possible , just for the challenge.

Chuffsy, were you able to source those ICs? I wonder if your problem is caused by what happened to me, where 1 of the 4 tiny coil wires broke off of its terminal. Those things are so fragile and I'm pretty sure it broke while I was desoldering the terminals from the PCB. I just happened to notice it while I was putting things back together. I don't know how the gauge would work with only 3 of the 4 wires connected...

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Matt L. -- Cary, NC -- 1991 740 wagon