Erratic gauge readings

[TTM]

Hello everyone,

For several months the voltmeter gauge on the right gauge cluster on my S2 has shown erratic values, always showing more than it should, like 16V on the drive.
As I'm confident the actual voltage is correct, it hasn't really bothered me, until yesterday, as as I parked the car in heavy rain for 10 min while shopping, the oil pressure gauge would show less than 2 bar at tickover when I started it, instead of the usual 3.5 bar.

Under load the gauge still shows 4.5 bar and the engine performs exactly like it did before sitting in pouring rain, so I'm beginning to think that the erratic reading of the voltmeter may now be spreading elsewhere...

Any suggestion on how to put in evidence faulty gauges? Electrics and I have never got on well...

Thanks.

 

[sulzeruk]

Check your battery voltage as the diode pack on your alternator may be open circuit over one of them resulting in overcharging which can cause erratic readings. Get the clockset out and clean all the small bridge connections to make sure there is no corrosion there.
Alasdair

 

[DavidL]

Take the gauges out and clean to 2 metal brass (?) prongs that locate into the back of the gauage. These sometimes give a bad connection and hence odd readings.
I'd say its tellling that its the same gauge, rather than say the voltmeter and temp gauge, so that it perhaps leads to the fault being at the common part namely the gauge itself.

 

[bmnelsc]

Pelican parts has an article on their site about strange behavior - mostly has to do with grounds on the instrument cluster and gauges. Look at Pelicanparts.com for an article titled....


Solving Strange 944 Gauge Problems__.htm

 

[TTM]

Well the oil pressure now reads back to normal.

Thanks for the tips, I will have a check.

 

[George Elliott]

In a word "Earths" the straps from Body to Battery, Engine to Body

Good to hear its returned to normal, was the weather damp / wet while the problem persisted?

For what its worth, the earth straps are all heavy duty crimped on our cars, and in a similar situation some years back I cross drilled the crimped on P-Clip on the earth strap to the battery with a 3mm hole, and then using a gas torch (as per solder plumbing fittings) I heated the clip & flowed a few grams of solder into the hole until i could see the solder migrating out of the clip into the strands of the strap. That created a molecular joint when the flux cleaned the way for the solder. The joint had developed resistance I guess from corrosion.

Good luck
George

 

[TTM]

Well yes, it returned to normal after we entered a dryer environment (been spending a couple of days in Provence).

I don't have my tools with me - unsurprisingly they almost always stay in the turbo [8|] - but will have a look at all this when I get the chance.

On a side note I replaced the O2 sensor before leaving down and I'm baffled how much better the engine runs.
I had bought this spare O2 sensor from P some 7 years ago and never took the time to replace it before as I thought the engine ran well enough.
At 120K miles the original one was probably due for replacement as it was all black when I took it off.
We put it on Sly's daily 944 S which originally didn't have one (M150) and though it helped when the engine was running cold it didn't help when the engine was warm. We then stumbled upon the old one among my 968 engine spares (which I used for the 3.0T build) and Sly mentioned it worked much better.

Anyway my S2 engine now runs smoother, idles almost as clearly as the turbo that's got a modern aftermarket ECU, feels smoother under load, average MPG increased from 28 to 30+ mpg, and this very subtle but slightly annoying engine stumble when slowly engaging the clutch in first gear has totally disappeared.
I love this car even more now, did I mention the S2 was far better than the turbo? []

 

[Diver944]

ORIGINAL: TTM

On a side note I replaced the O2 sensor before leaving

Was it easy to get the original one out? Twenty plus years inside a hot exhaust must have been pretty much seized solid in there

 

[DavidL]

ORIGINAL: TTM

did I mention the S2 was far better than the turbo? []

Far too much Chateauneuf me thinks....

 

[TTM]

ORIGINAL: Diver944
Was it easy to get the original one out? Twenty plus years inside a hot exhaust must have been pretty much seized solid in there

This is what I expected too but surprisingly it made no resistance. Maybe I was lucky.

Where I have not been so lucky is that the car last evening suddenly developed a misfire on the autoroute. I haven't been able to identify the problem so it will have to be transported back home - first time in 10 years my "lovely" S2 has left me stranded []