Speedo reading gone wonky

[1I1]

The other night when driving home the speedo in my Corolla suddenly dropped to 90km'h while travelling at 100. As quick as it dropped it shot back to the correct speed.

Then this afternoon it started to play up again. I had to slow down to about 40 in town and the speedo kept dropping right down to 0 and stayed there. I started to accelerate (going into 70k zone) and the needle just bounced on back.

I have hooked up an Apexi RSM (which during all of this carried displaying speed) so thought perhaps its causing the issue. Checked connectors and they all seem ok.

Even disconnected RSM and went to drive down the road to find the needle bouncing around like an old 80's car with worn speedo gear/cable.

Thoughts?

[matt dunn]

Faulty speedo sender,

And yes it can affect one gauge and not the other when they both read off the same signal.

Matt

[Akane]

Is it possible to have stripped gear on the sender.. although 1 in a billion chance....... shrug........

[1I1]

@ Matt thats good to know! I've pulled the speedo out already as was going to send it away so will see if I can borrow a sender from wreckers.

@ Kenny - Initially thats what I thought but then looked at RSM it was reading normal (well from what I could tell)

[matt dunn]

Is it possible to have stripped gear on the sender.. although 1 in a billion chance....... shrug........

Missing a tooth would either kill it or have no effect,
Enough stripped teeth and it would stop completely.


It is AE101? S/h senders for that era are getting hard to get, as they corrode off the 5V feed wire and are a real common problem,
that usually kills them completelt, but they do also start to drop pulses out of the signal which can only really tell on a scope.
Same thing happens in Isuzu's but they affect the Auto trans and not the speedo.

It's all to do with the sample rate that the device uses from the sender.

[Dell'Orto]

Pretty much, you've used 3rd gear VTEC too much, its bound to happen.

[captain crescent]

its because the car never sees past 99.99kph mark

[1I1]

Thanks Matt. Cars a AE111, local wreckers still have a few so will try. Yeah could end up with same issue again down the line with 2nd hand supose.
Had suggested to start with contact cleaner on the terminals incase it's just a bad contact. So will start with that

Brad - Pretty much, possibly caused by me putting a two stage vtax adjuster in and been tec'n too much.

Craig - ...I'm just going to ignore you

[2LTR Rona]

[
It is AE101? S/h senders for that era are getting hard to get, as they corrode off the 5V feed wire and are a real common problem,
that usually kills them completelt, but they do also start to drop pulses out of the signal which can only really tell on a scope.

Same thing happens in Isuzu's but they affect the Auto trans and not the speedo.

It's all to do with the sample rate that the device uses from the sender.

@ Mark - I'm stealing your topic for a second okay (Strut worked a treat btw, cheers for that)

@ Matt - would that common problem in the AE101's also result in the speedo fluctuating i.e. bouncing plus or minus say 10 Km/h (as an example) ??

[1I1]

All good.

Guess if the pulse is being interupted it's likely that the needle will bounce around. That's part of my problem now too (is it just me or is it kinda amusing seeing the needle do that?)

[2LTR Rona]

thats what i would assume, but we all know what assumptions do

nope its not just you, I'm so use to it now that i drive more by gear / rpm, till someone in the passengers seat notices it & asks wtf is going on

[KIPH8N]

I got the same problem in my ae101 levin too..but cant find da spedo sender..

[1I1]

Swapped speedo sensor over and took car for a good 10k drive. Seems to have sorted it

KIPH8N - They are located just above the diff right at the back of gearbox.

[1I1]

Looks like speedo sensor didn't sort it

Driving along at 50km/h last night speedo was reading 0km/h yet the trip meter and odometer were working fine along with RSM.

And out in the country while doing 100km/h speedo was reading around 80

[sergei]

Looks like speedo sensor didn't sort it

Driving along at 50km/h last night speedo was reading 0km/h yet the trip meter and odometer were working fine along with RSM.

And out in the country while doing 100km/h speedo was reading around 80

This would point to fault between the needle actuator and needle actuator circuit (most likely dry joint there).

[whynot]

you tried checking the earth points around the engine bay and dashboard? I had issues with sensors a few weeks back and it was just a bad earth. wasn't obvious but I sanded them up then soft sealed them afterwards. All fixed after that