AUTO Q AND A:What might be cause of speedometer, odometer working intermittently
Q: I have a 1995 automatic Honda Accord LX and the speedometer and odometer work intermittently. I noticed that both work (but not always) on warm/hot days and do not work at all on cold days. The car has 120,000 miles. The dealer and mechanic wa...
Q: I have a 1995 automatic Honda Accord LX and the speedometer and odometer work intermittently. I noticed that both work (but not always) on warm/hot days and do not work at all on cold days. The car has 120,000 miles. The dealer and mechanic want more than $800 to fix it. Can I fix it by myself? Can you give me any ideas about the best way to fix it?
A: Intermittent problems are the most difficult of all to solve and it sounds like your repair folks are preparing you for a worst-case scenario -- replacing the gauge cluster. You made huge progress in the diagnostic process by noting the conditions when the fault is most likely to appear, or not. Since the speedometer and odometer on your Accord are electrically controlled, and temperature is a factor, this smells a lot like a poor electrical connection -- the question is where. Your Accord, like most modern vehicles, employs a VSS, or vehicle speed sensor, attached to the transmission, which creates a pulsing electrical signal that's proportional to vehicle speed. Several vehicle systems share this signal; the instrument gauge cluster, the cruise control module, and the engine and transmission control computers.
In a follow up Q&A message you indicated the cruise control does not work (regardless of speedo/odo functionality), the check engine light does not come on, and the D-4 (shift indicator) lamp does not flash. Assuming the Accord is driven at least some distance during one of its episodes, this tells us the engine and transmission control computers are consistently receiving the VSS signal. Had the VSS signal not reached them, their built-in diagnostics would have identified the error. There's apparently also a second fault, affecting the cruise control system.
I consulted the wiring diagrams for this circuit and found the gateway (splice) for all the interested parties, and it's behind the instrument panel. Since the fault must be after this point (on the individual path to the speedo/odo), it's location may lie in an electrical connector behind the driver's side kick panel, the connector on the back of the cluster, or inside it. Try this: during an episode, grab the instrument panel with both hands and twist it, or give it a firm smack or two. If the symptoms change, you're very near the problem.
This is, I believe, a pro level job. If you feel up for some detailed testing and disassembly, a #276-271 12V green LED with holder (about $2 at Radio Shack) makes a great tester for this type of electrical signal. The orange VSS signal wire could be checked for activity at various locations, as well as within the gauge cluster. Check with your public library to see if they have ALLDATA or Mitchell on Demand. These are professional automotive repair databases that provide fairly detailed circuit and connector information. Should the fault lie within the instrument gauge cluster, I'm confident it could be repaired, with a little diligence. Similarly, a loose connection in the wiring, once found, would be easy to fix.
(Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose. E-mail email@example.com . He cannot make personal replies.)