Speedometer goes to zero under hard acceleration

[E30M42]

Seems I have a loose wire or bad gauge.  

Wondering if any has experienced a similar problem.

Under easy acceleration speedo is fine.  At steady speed speedo is fine.

Accelerate hard and speedo goes to 0.

Checked the wires at the diff and they seem fine.

Really don't want to pull the cluster..but I may.

Anyone seen anything like it??

Ric

[E30M42]

More info.

It is consistently "G" sensitive.  once you hit a certain G force the speedo stops.

I can't imagine it is a wiring harness since it is very consistent about the g force level.  I am thinking gauge.

Anyone else seen it?

Ric
1991 318i
HR sports
Koni SA
325is seats

[Febi Guibo]

hey, I would check the speedo sensor ...it's on the back of the diff ...make sure the cable is in good shape, and the sensor is in tight.

worst case, you get a new sensor, not expensive.

if the speedo works at the cluster it's prolly the sensor at the diff.

[silverblades181]

I'd say you have a faulty sensor. It's about 30$ at the dealer.

[johna]

A friend's 318is had a similar problem. Turned out to be that the wires to the sensor, just before the plug, had suffered corrosion and were broken. You couldn't see it as it was beneath the insulation.

Have a good look at the wires around the plug and maybe strip back the insulation to be sure.

[E30M42]

Thanks guys...I will focus on the sensor first.

Changing diff oil is on the list of things to do anyways...so I will knock that out while I am there.

Will repost here to let you know if it works.

[2002maniac]

A friend's 318is had a similar problem. Turned out to be that the wires to the sensor, just before the plug, had suffered corrosion and were broken. You couldn't see it as it was beneath the insulation.

Have a good look at the wires around the plug and maybe strip back the insulation to be sure.

I've seen this happen a few times including my own car.

[E30M42]

The wires going to the sensor are VERY fine gauge.

Every time the diff moves (on and off the gas) it flexes them, and just like the paper clip bent back and forth, one failed.  The wire was broken inside the insulation.

I rewired both and added a loop to allow the system to flex a bit more.

Main problem was that the wires are tied to the chassis just above the diff in a plastic clip.  Had there been a bit more slack it wouldn't have happened.

So when you go under the car next unclip the plastic clamp holding the wires, pull a bit of slack through and then reclip it.

Sensor was fine.  

Speedo back to normal.

[Scumball]

Mine's the same when very wet... Just haven't been bothered to do anything about it yet.

We get salt on the roads most of the year over here in the UK, so you can imagine how often this happens over this side of the pond.