Browse › Tech ›FAQs and how-tos
Hi guys!
Last summer, I noticed my 85 hatch speedo would read 3-5 mph low when the sun had been hitting the front of the car for a few hours. Figured it out based on tach reading vs speedo. Any idea why this happens? Would like to correct it if possible now that it is finally warming up again in WA.
Thanks
rednucleus on 08:30:56 PM / 25-Apr-20Hi guys!
Last summer, I noticed my 85 hatch speedo would read 3-5 mph low when the sun had been hitting the front of the car for a few hours. Figured it out based on tach reading vs speedo. Any idea why this happens? Would like to correct it if possible now that it is finally warming up again in WA.
Thanks
Analog
It's all mechanical so I have a hard time getting my head around a cause for slower reading in higher temps. Tire size changes can alter the speedo but I can't see heat doing much to a gear driven cable.
What do you think?
It's all mechanical, but if memory serves there is not a direct physical coupling of cable to actual speedo needle? Wish I had a spare one to look at!
It's a significant change - usually 5th gear 3500 rpm equals 70 mph. When it's been in direct sun for a few hours, 3500 drops down to about 65-67. First noticed this going to my Wed afternoon skis; 30 minute freeway drive. By the time I leave it's cooler and reads correctly again.
The cable is directly connected to the speedo at the back of the meter. My problem with the speedo was the needle jumping erratically and I think it settled down a little when the car warmed up. All I can remember was I tried putting wd40 and it made it worst so I used rubbing alcohol to clean off the wd40 and used lock graphite to lube. I think I have to clean the meter and I lube the cable with graphite, it was a long long time ago. I do remember there was a crack in the back of the plastic meter housing where the cable is attached to and I sealed it with either model glue or abs pipe cleaner and wrap electrical tape to seal it. My guess was something came out of the cable and contaminated the needle. In your cas I would try cleaning the meter and lube the cable?