Technical Tachometer sticky needle?

[gijoe]

Hi guys,

I've been through tonnes of threads, but I need a little guidance here. My beloved 99 Marea Weekend 100SX 1.6 16v is showing its age little by little Some months back I removed the instrument panel to replace a pesky burnt out bulb since I drive a lot at night especially in the winter, and occasionally it would be nice to see the mileage and engine temp!

That operation in itself is a total pain in the proverbial, but more annoying is the fact that the tachometer stopped working normally shortly after. What happens is that for the first 3 minutes of drive the needle lays flat @ 0 rpm, then it springs to life and reads normal after that. Nothing wrong on the engine side I can hear, and driving normal as she has done for years. All other instruments work fine.

Just 2 days ago before the NCT, I thought that other burnt bulb needs replacing. Now the tachometer needle dies randomly. Engine still purring away, but the needle can go mid drive, and then spring back to life again. If I tap the panel a good bit I get a reaction, or sometimes not. This leads me to think there is a contact problem at the back of the panel. When removing the contact block to take out the panel, I didn't notice any dirt or bent pins :bang: Where is the problem?

And if it is/was a contact problem why when the problem originally manifested itself, did it work religiously after 3 minutes from engine start, and not with a tap on the panel?

Incidentally, would an air leak above or below the lambda probe cause a high reading (lean mixture) at the test centre?

Many thanks guys,

Joe

 

[bpetersb]

The fact that your problems only started after you had disturbed the instrument pod does suggest that this may be a connection problem.

First thing to do is to remove the instrument pod again then clean and check all the connections. Have a really good look at the circuit board on the back of the pod to make sure you didn't crack one of the tracks when you removed or refitted the multi-pin plugs, the plugs can be a very tight fit causing the circuit board to flex quite a lot when you remove/refit them.

I have seen cracked tracks on a circuit board work intermittenly before, possibly because heat from some source may have expanded the material a microscopic amount and caused the circuit to make or break. Good luck

 

[gijoe]

Thanks Peter,

True, those connectors are a sod to get off, and it would be very easy to damage a delicate board. If a cracked board is the cause, am I looking at a new pod or board, or is there a fix with solder? Would a cracked board around the track area not affect more instruments?

Cheers,

Joe

 

[bpetersb]

If you find a damaged track on the circuit board there is no reason why you would not be able to bridge it with a bit of solder, or even by soldering a small length of wire across the crack.