Biturbo 2.8 Speedometer

8

89Spyder

New Member
Messages
11
Hello,

Got a 'new' 1989 Biturbo Spyder and the speedometer is not working. I pulled the instrument panel and moved all connectors - but nothing changed. Then I went under the car and checked the sensor at the end of the gearbox. It has two wires and all look like brand new. The car has only 8000 miles and it is probably true because all looks like new. Any suggestions on possible tests to narrow down the search?
 
Oneball

Oneball

Member
Messages
11,119
If you’ve got a multimeter first thing I’d do is check you’ve got power to the sensor.
 
8

89Spyder

New Member
Messages
11
Hello Oneball,

Thank you for your advise.
Today I checked the Volts in and out of the sensor (at the exit of the gearbox) and it was 2.23V in and out. Then I disconnected the red and white wires and the red read 2.23V and the white zero. So, I think, if there is some coil inside the sensor, then it is OK - so sensor must be good.
Am I right?
So where can I catch the other end of these wires (fuse box, instrument panel)?
Any suggestions for the next step?

Joe
 
Oneball

Oneball

Member
Messages
11,119
Usually on a car of this age the power to the sensor will come from the dash itself, there probably won’t be a separate module. So if you’ve got power at the sensor I’d say chances are the wiring’s ok. If you’ve got a wiring diagram you’d be able to confirm. So I’d guess either the gauge itself is faulty, the sensor is faulty or the trigger has fallen off the output shaft.

I think my next step would be to connect the voltmeter across the sensor, jack the car up and turn the prop shaft and see if the reading fluctuates. The only problem with that is some digital multimeters are so heavily damped you may not read the fluctuations of the sensor.
 
8

89Spyder

New Member
Messages
11
Dear Oneball,

Thank you for this great info.
Is there a similar description to diagnose the speedometer?
Looks like in my case there is power to the sensor but nothing moves at the speedometer end.
I don't mind buying a new sensor but first would like to make sure that the speedo is OK.
By the way, I also have a 1984 2.0L Biturbo, and even when I stop, the speedo works and show like 5KM/h, and the odometer moves too.

Joe
 
CatmanV2

CatmanV2

Member
Messages
48,789
89Spyder said:
Dear Oneball,

Thank you for this great info.
Is there a similar description to diagnose the speedometer?
Looks like in my case there is power to the sensor but nothing moves at the speedometer end.
I don't mind buying a new sensor but first would like to make sure that the speedo is OK.
By the way, I also have a 1984 2.0L Biturbo, and even when I stop, the speedo works and show like 5KM/h, and the odometer moves too.

Joe
Click to expand...

Personally I'd do the diagnostics on the sensor first (apart from anything else you have the info to determine the function of the sensor)
At the very least you'll be able to confirm the problem *is* the speedo. Best case, you can fix it with the sensor.

Ref the 1984 sure there's not a pin to stop the needle dropping to zero on the gauge? Although that won't account for the odometer moving, though.

C
 
CatmanV2

CatmanV2

Member
Messages
48,789
Another observation from the page that @Oneball referenced is that all those sensors use 12v, not 2.23v (which seems a very odd number)

So (assuming that one of those sensors is fitted to your car) one would expect 12v on the green wire (or at a guess) shielded connecter on a type 2

C
 
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