Electrical gremlins...

[Winso]

I posted a while back about my coolant warning light randomly flashing when the revs hit about the 3.5k mark. I tried a few things including cleaning up the earth to the rocker cover and swapping round the wires to the sensors but it's still doing it, only thing is now the rev counter does odd things when it hits 3.5k as well. Best way to describe it would be that it sort of 'twitches' when it gets to about 3.5 - 4k, it will shoot about 500rpm higher then drop about 1k then steady its self over about half a second. Engine runs fine and is not revving like the counter shows. Usually if the rev counter twitches the coolant light gives 3 flashes as well. If I get it past about the 4.5k mark it's fine all the way to the redline with no more flashing/twitching. I'm certain its an electrical fault somewhere, any ideas where guys?

(car is a 90 spec valver)

[CHRIS_MC]

not wanting to p!ss on your chips mate but, it started to happen to mine, 90spec 16v, effectively coolant was starting to leak into the cylinder head, (i did burn myself on the filler bottle)  it started to use more and more water/coolant till eventually from turning it on from cold the temp light was flashing,

i used to coast along keeping the revs low, thinking some sort of electrical fault was occuring, so i hope for your sake thats all it is

my cylinder heads were all pitted and needed re-skimmed, basically shelled out far too much money, and would have been better off sourcing a recon engine, rather than a reskim.

[Conker]

If the Hall Sender inside the dizzy i faulty or gets too dirty, it will give you weird rev counter issues. Clean it out with WD40 and check the connector as well. MIne started playing up and cleaning it helped but it took a whole new dizzy (I couldn't get mine to disassemble) to finally fix it.

I doubt a failed head gasket would give you the rev counter issues your having. Is it using up coolant quickly?

To be honest, this sounds like an issue with the clocks themselves though. If its driving nicely, nothing to worry about too much.

[Winso]

Thanks for the replies guys, I was thinking maybe hall sender related, I'll give the contacts etc a clean and see what happens.

HG was fooked when I bought the car so its had a decent skim and new gasket about 2k miles ago so I think I'm ok on that front, not really using any water at all.

Coolant light even flashes if I take it past 3.5k with the oil temp at <60 degrees (which I only did as a test!) so I'm prety sure nothing's actually overheating in there.

It's just odd how it plays up right at the start of the power band.

[rubjonny]

fact the light flashes at same time suggests its not hall sender but a wiring/dash problem!  have a look at the dash plug, make sure its in fully and the pins/wires aint damaged.  Pay close attention to any brown (earth) and black/red (rev counter) & black (ign live) wires back to fusebox.  Have a look at the black/red plugs/wires to the coil too, sounds like its loosing the rev counter or ign live signal momentarily and thinks car is switched off triggering the coolant light test sequence?

[Winso]

Cheers for the advice jonny, I'm only now getting a chance to have a look into it!

First stupid question.... Where do I find the dash plug?

[rubjonny]

if you take off the dash under tray on the driver side you should be able to see the dash plugs, plus you can have a good look around the fusebox too

[Winso]

Ah, I was having a poke around the fuses, all looks OK.... but what are the larger square things above the fuses? No. 72 wasn't in properly so I sorted that and now the rev counter seems to behave its self. Coolant light is still flashing but at least I'm getting somewhere possibly....

[Conker]

Ah, I was having a poke around the fuses, all looks OK.... but what are the larger square things above the fuses? No. 72 wasn't in properly so I sorted that and now the rev counter seems to behave its self. Coolant light is still flashing but at least I'm getting somewhere possibly....

They're relays.

[rubjonny]

72 is the rear wiper relay so id be surprised if that fixed it
but one of the other relays may have helped or you have a loose connection around there