hey folks... this rev-counter is still bugging me... i know i should just give up and leave it how it is... but i want it to work!

Am i right in thinking that the signal for the rev-counter comes from the coil? So maybe the fact that it isn't working properly/all the time maybe a broken coil... or wire from it that goes to the ECU... but then if the wire from the coil to the ECU was broken then there would be running problems as the ECu wouldn't be recieving the signal from the coil to say that it sparking and working properly...

Grrrr

Phil:confused:

If you have a felicia Haynes, on page 12.24 (wiring diagrams at the back) there's a yellow wire from pin 9 on the connector from the ECU to the tachometer (rev counter).

I can't say I know for certain but I have a sneaky suspicion that with the Bosch monomotronic system the rev counter value comes from the hall sensor. So if your engine is running fine my guess is the problem is either the wire between the ECU and the rev counter or the rev counter's earth connection- or the rev counter itself. Changing the instrument panel is probably the easiest thing to do in the first instance though, if not already done.

the signal does comes from either the crank sensor or the hall effect switch indirectly, without the sensor working you wouldn't get an rpm signal at all, but then also the engine wouldn't run either....

the wire in the dash loom for the rev counter is indeed yellow as mentioned above, but be carefull because on some models it changes to a different colour in the engine loom via the two multi-way connectors next to the battery, on some it's a black wire, and on another type i've seen it's back with a green tracer...

a good way to test it without taking the dash apart is to back probe that wire via the multi-way connector using a multimeter that can measure frequency as this will tell you if you are getting a signal or not... to be honest i doubt very much that it it's a broken wire unless the loom has been fiddled with

Well.... the dashpod and rev counter have been changed (different problem needed fixing). So it obviously isn't a problem there... the crank sensor has been changed but as said if either of those sensors weren't working then neither would the engine.

I have looked at all the wires coming from the ECU and there is no yellow wire.

It is rather confusing as the rev counter only kicks in when the rev are high and only sits at 4500rpm then falls to zero again... but on odd occasion it will work perfectly!

Damn thing!

Thanks guys

Phil

It might be a fault in the d@mndest of places. I had something similar with my Xantia diesel, and the break was in a wire to the glow plug controller. So maybe it's nothing to do with the tacho signal itself, but the cold start enrichment (which you'll not have needed this weather).

Cold start enrichment?! lol... never heard of that.

Will have another look and fiddle once it stopped raining long enough.

Like i say not a big deal but would really love for it to be working.

Thanks

Phil

yeah, you will have cold start enrichment, but this is something the the ecu does seemlessly without you even noticing... basically what it does it injects more fuel and advances the ignition spark to allow the engine to run smoothly, it gradually reduces the enrichment as the coolant temperature increases

I always thought it was noticeable in that the idle revs fall down slightly when the car is warmer?

yes that is true, the idle speed is increased slightly too to allow the engine to run smoothly at tickover

I have exactly the same problem; the rev counter only kicks in when the revs are high and only sits at 4500rpm then falls to zero again, sometimes it works properly. My car does not have an ECU or crank sensor since i have a carb not injection. I wonder where the rev counter gets the signal from?? :confused:

Maybe need a new revcounter??

strange... must be a fairly common problem.

Ihave tried a new rev-counter but that didn't fix it. Must be to do with the feed to the rev-counter or whatever controls it.

phil

The rev counter on my 1995 favorit glxi estate also had the same problem. I say used to because I gave the car to my dad a couple of years ago and the fault has virtually gone. he only pootles about though, and i would say he rarely goes over 2500 revs. I also found that low revs would mean the rev counter was more likely to work. just ignore it - electrical problems are a nightmare to trace!

This is still really bugging me

I know it isn't a big deal and I should just ignor it but it drives me mad why it won't just work!

A few weeks ago I tried to tap into the wire... that being I took a wire from the rev counter output on the ECU and straight into the back of the instrument panel without the existing wire there and still it didn't work so it can't be a break in the cable to the dash.

So it has to be whatever gives the ECU the signal? Anybody any ideas? Alternator, crank sensor?

Or the ECU itself but without having a spare ECU lying around I can't test that theory!

Thanks

Phil

if the crank sensor was giving false/missing signals the engine wouldn't start, remember, he ecu also needs this signal for ignition triggering, my guess is a fault in the instrument cluster somewhere

Well.... the dashpod and rev counter have been changed (different problem needed fixing). So it obviously isn't a problem there... the crank sensor has been changed but as said if either of those sensors weren't working then neither would the engine.

I have looked at all the wires coming from the ECU and there is no yellow wire.

It is rather confusing as the rev counter only kicks in when the rev are high and only sits at 4500rpm then falls to zero again... but on odd occasion it will work perfectly!

Damn thing!

Thanks guys

Phil

in my car the rev counter is conected to the ignition coil, on the negative side, its a yellow wire... maybe if you have a spark enhancer is conecte bad or something of such

if the crank sensor was giving false/missing signals the engine wouldn't start, remember, he ecu also needs this signal for ignition triggering, my guess is a fault in the instrument cluster somewhere

Yeh thats true and it has been replaced fairly recently.

The only thing is that the instrument cluster has been changed already! (temperature guage and fuel guage not working) and also the rev counter has got a brand new unit in!

Phil

:rubchin:

i suppose it might be a fault on the ecu then, have you got a multimeter than has a frequency counter??

I'm not sure but i have heard tale that the rev counter is somehow tied into the alternator? Don't ask!!!! I have noticed in these darker times that the battery light glows very very faint when cold with lights, heater blower heated rear window and wipers on, it never gets dimmer or brighter so the revs don't affect it going out, only turning off the various electrical loads. It is okay with just the lights on and the heater blower on 1. Suspect its the good old regulator will be changing soon and will let you know if it cures the rev counter as well:(

I'm not sure but i have heard tale that the rev counter is somehow tied into the alternator? Don't ask!!!! I have noticed in these darker times that the battery light glows very very faint when cold with lights, heater blower heated rear window and wipers on, it never gets dimmer or brighter so the revs don't affect it going out, only turning off the various electrical loads. It is okay with just the lights on and the heater blower on 1. Suspect its the good old regulator will be changing soon and will let you know if it cures the rev counter as well:(

The reason or that is the voltage regulator, in a car electrical system everybody thinks is 12volts, its actualy 14.4volts and 13.2 nomila current, when the car's batery reaches <13.2 the voltage regulator tuns the alternator to charge the batery, when the batery reaches 14.4 the voltage regulator turns off thats how the batery never gets overcharged

your entire car runs out of the batery's power supply, the alternator is only for chargin the batery, tihs helps fuel economy as well since the alternator produces a load on the engine, not a lot, but a load, also the alternator doent kick in to charge unless its running above 14.4 and decents amps, that from 800rpms or more, and ofcourse, when higher revs, the voltage regulator only sends out 14.4 volts non the less,

so if you see your light dimming on iddle or your engine runs a roughfer iddle when you turn on accesories, its time to replace the batery...

a little trick, if that happens, let you batery die out, remove all the fluid from it, clean it with abundant soda (pour soda, shake the batery and then drain the black soda until it comes out transparent) clean the outside while your at it, replace liquids with batery acid until the sell get covered and top it off with water(distilled) and put it to charge... whoala!!! batery is good for 8 more month (2nd reason why i dont buy gel bateries, first is if they get totaly decharge theyr damaged)

and clean the poles an check for good earth conection while your at it