TOOLMAN1966

I had the Speedometer indicating 20mph and Odometer not working problem, half the time. The other half it worked perfectly. Mine is a 1998 Civic EX. My problem was a broken solder connection (often called a "cold solder joint") on IC1 pin 10. My circuit board is the one pictured by REVOAPPAREL in this thread on 8-15-2012. This pin is one of the epoxy (or glued) pins. I used the soldering iron to remove this epoxy from the pin before re-soldering it. (The heat kind of crumples the epoxy so it can be scraped off with the iron tip.) The Vehicle Speed Sensor signal comes into IC1 on this pin, but also on IC1 pin 12, and IC2 pins 10 and 15. __ I found which solder connection was broken in the following manner: Removed the circuit board from the speedometer/odometer mechanism (it pulls right off.) Attached a 12 volt power supply to IGN and GND. Used a voltmeter to read COS & SIN voltages. These 2 voltages tell the speedometer needle where to point. (RED voltmeter lead on COS+ and BLACK voltmeter lead on COS-.) (Don't look at the voltages with respect to GND. The speedometer doesn't see that.) When the circuit board was working correctly, the COS voltage was 5.04 and the SIN voltage was 0.26. These are logic levels ONE and ZERO. (If you remember your Trigonometry, the COS of zero is ONE and the SIN of zero is ZERO. Zero is the vehicle speed.) When the circuit board wasn't working correctly (this is when the needle would indicate 20mph IF it was attached) COS voltage was 2.47 and SIN voltage was 1.80. When I read these WRONG voltages, I started touching things and when I pushed on IC1 the voltages became correct for a moment. Then I used a probe to push against each IC1 pin individually and found pin 10 was the pin not making contact. __ A person should be able to use this technique to find a bad solder joint anywhere on the board causing incorrect speedometer readings when the vehicle is sitting still. ___ I also traced out the entire circuit board and drew a schematic. If I figure out how to post a scanned pdf of this, I'll attach it. ___This is my first post to any automotive thread. I sincerely hope this helps many of you out with your speedometer indicating 20mph problems! Enjoy Troubleshooting! ((Toolman1966 _ APRIL 14, 2013))

Stockings

I tried re-flowing the solder on my 96 Accord, and was amazed to see the speedometer come back to life. Strangely, the solder joints looked perfect, with no cold joints (I once worked as a solderer), but one of them must have been bad.

The hardest part of the job was soldering *through* the epoxy covering some of the IC pins. I couldn't remove the epoxy, even with heat; but the tips of the pins were sticking out from the epoxy, so I just heated them a bit, and said a prayer.

Back at the factory, we sometimes got cheap components (contaminated or oxidized) that refused to bond with the solder, and I'm guessing this occurred on these boards, probably all from the same supplier.

The quick cure for such a component is to use plenty of flux, and to gently scrape against the lead with the soldering iron. The scraping, along with the flux, will often displace enough oxidation to allow the solder to bond to the lead.

I didn't find it helpful to add additional solder, which tended to bridge across adjacent IC pins (which, if ignored, would cause disaster). Easiest to use paste flux. After soldering,thoroughly clean board with rubbing alcohol and Q-tips.

Thanks, all, for the info and suggestions – saved me a bunch of money. All in all, though, I'm thinking the old-style speedo cable might be the superior solution. :-)

chris cooper

I've just recently decided to start driving our Accord to work. The speedo has been intermitent for years and I haven't really cared. Thought I would look into it today and bam ended up here on this forum. Needless to say, I will be pulling this board and doing some soldering tonight.

baceman007

Hey guys. Thanks to Honda-Tech I got to the point where I was able to remove my speedometer and get the needle off. I found out that the worn out gear in my speedometer trip meter is the white tenths gear and would like to replace it. I was wondering how to remove the trip-odometer and where to get a new tenths gear. Sorry if this should be a new thread, seemed like it was related to this post. This is to a 1993 Civic del Sol btw.

glenn0

This is in response to Toolman1966, posted 4/15/13. This fix worked perfectly for my '96 Civic. The cold solder joint was at IC 1, pin 10 just as he said. Careful inspection with a magnifying glass showed that the solder had not flowed from the pin to the printed circuit board trace. Epoxy had been used (for some unknown reason) over pins 1 to 10, but i could not break through the epoxy without damaging the PCB. The top of pin 10 was sticking out above the epoxy just a bit so i took a short 1" jumper of #22, solid, insulated wire, and stripped off 1/8" from each end. I made a little loop on one end, wrapped it around the tip of pin 10, and soldered it with my little pencil iron. Then, following the trace that should have been soldered to pin 10, i soldered the other end to an exposed solder pad on that trace. Since PCBs and ICs can be damaged by excessive heat, it is important to be careful. Don't use flux, but use regular 60/40 solder that has the flux inside - the pencil iron and solder are available from Radio Shack or any electronics supplier.

kenzo42

My speedometer jumps all over the place. Does this not sound like a bad solder joint?

Jmb106jr

Sounds like VSS.