Electronic Speedo Issues

[FerneyO]

I am having intermittant problems with the electronic speedo on my 2013 Caterham 7 (Roadsport 170). I wonder if anyone else has seen this problem & if a solution exists.

Here is the problem: When the car is cold and just starting, the speedo works fine, then as the car warms up, like 20 miles the speedo starts to go intermittant with the needle fluctuating wildly. Eventually after several more miles the speedo zeros out and stays there. Its worse on hot days, and on cold mornings I can sometimes drive 60 miles before it goes bad.

What I tried: When the problem starts to happen, I sprayed 'Freeze-spray' (used for electronics diagnosis) onto the speedo and it started working fine again for ~ 5 miles before going intermittant again. This led me to suspect a failing chip inside the speedo. So I got a replacement speedo from Caterham, but is shows exactly the same problem.

......Dave.

[Sean]

I have had a similar problem, but with the oil pressure gauge. In my case, the cause was a dodgy earth connection, and the solution was to remove the nut holding the wiper motor (I think) under the dash on the right-hand side, just behind the knee trim panel. Once the panel is removed, the nut with the grounds going to it is apparent. I then scraped away some paint at the contact area, applied a dab of conductive goop, and re-assembled. I learned all of this from searching the Tech Talk section of the holy place for 7s (Blatchat).

[FerneyO]

Hi Sean,

yes, found the grounding point. It measures 1.4 ohms to battery -ve and 8 ohms to the aluminum body panel behind the knee trim.

I'm going to run a wire from the battery to the grounding point.

Thanks.

....Dave.