Intermittent Speedo

Jago Bret

Jago Bret

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Hi,

I have a problem with my speedo on my CS2800.

What happens is that it works fine from cold but after a while ( and always after stopping for a period - e.g fuel stop) it stops working.

It's seems like it's related to heat build-up maybe?

I should say the car has a 5-speed overdrive gearbox conversion undertaken by a previous owner and bought through W&N.

I have a spare speedo which I could fit but a) I would want to be sure that it was the speedo is at fault as I really do not relish pulling the dash out.

I did the speedo drive 'end' the last time I had the car on the ramp and couldn't see anything obviously wrong.

If anyone has experienced a similar problem or has any bright ideas I would love to hear from you.
 
Is the odometer working/ failing at the same time as the speedo? If the odo doesn't stop moving then it's defo the speedo internals
 
Cable may just need to be lubricated with graphite spray from the speedometer head. Detach both ends & spray in the cable housing until it comes out the bottom.
 
Jago Bret said:
It's seems like it's related to heat build-up maybe?
Click to expand...

No, I wouldn't think so. I'd guess it's just flat out intermittent. But please check the odometer or trip meter operation and report back.

I would want to be sure that it was the speedo is at fault as I really do not relish pulling the dash out.
Click to expand...

Removing and replacing the speedometer does NOT require pulling out the dash. There are several threads here on e9Coupe.com about gauge removal/replacement, such as this one: https://e9coupe.com/forum/threads/speedometer-removal.2484/ Read HBChris' post #17 in particular. I have done mine the way Chris recommends and it isn't that hard (Hmm - you probably have a RHD model. I wonder if that changes things?)
 
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In order of preference to investigate....

Mechanic's Rule: when something goes wrong, look at where the last work was done. In your case, installing a five-speed (I've done it) offers chances to forget to snug things correctly, such as the speedo cable.

I'd expect the speedo to go Tango Uniform if the cable binds in its sheath: the speedo cable is driven by a gear on the trans which might twist the cable into a severe knot if the sheath is binding.

It could be that the speedo cable is barely engaged with the speedo head. You'll have to reach behind the speedo - a bit of bother - and ensure the large knurled cylinder securing the cable to the speedo head is snugged down well. If so, look at the cable connection to the trans. I disremember exactly how it's secured, but it's not a difficult thing and your job is to make sure that the cable is well and truly engaged with the trans. Your intermittent problem suggests to me that one end or the other is loose.

Although you say the speedo is intermittently on vacation, know the odometer fails when the 1/10 mile wheel starts slipping on the shaft running through the center of the number wheels. This repair is a little more involved and fiddly, you have to take the speedo out and open 'er up, ding the shaft, reassemble and reinstall. The odo can work without the speedo needle moving, they're driven differently (odo is mechanical, speedo needle magnetic).

HTH, I'm watching to see what turns out to be the culprit!
 
Thanks guys for your advices.

I’ll check firstly whether the odemeter stops working along with the speedo - I’m fairly certain it does but need to double check.

I’ll also check speedo cable to back of speedo which I haven’t done previously.

Like I said I have previously checked the cable to transmission connection and it seemed OK with nothing obvious.

I’ll post an update soon assuming the weather holds!!
 
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