aaddzz123 Posted June 17, 2014 Share Posted June 17, 2014 Right I've just bought a mk1 GT and the tacho doesn't read properly. When it idles it's a few hundred rpm low and it doesn't seem to read anything over about 3k if I remember rightly... I managed to get a little video the other day.Someone has already told me that they had the same problem and they ended up replacing the clocks. So assuming that it was a problem with the clocks I've taken them apart... There were a few signs that they had been opened before so there's a possibility that something been damaged or someone else might have just tried to fix it too in the past. The big plug closest to the tacho that goes on the back of the clocks has the clip broken off but it still sits inside the slot nice and tight so I don't think that's an issue. The rest of the clocks work fine too.Missing screwBroken clipI eventually got the tach unit out but to be honest I can't see anything wrong with it? Electronics aren't my strong point but there is no darkened area or parts that look damaged or burnt out.The bottom board in this photo is the tachometer part. The other cluster of boards is all for the boost gauge display.Anyone got any ideas what it might be to do with the clocks? If not I can only guess it's a problem else where on the car? But to be completely honest I have no idea how the tacho works lol!ANY help appreciated guys. Quote Link to post Share on other sites
aaddzz123 Posted June 17, 2014 Author Share Posted June 17, 2014 Don't see anything wrong with this side of the board either? Quote Link to post Share on other sites
daniel_g Posted June 17, 2014 Share Posted June 17, 2014 It gets a signal from the dizzy.Does the car actually rev over 3k and the dials dont show it ? Or will it not rev higher than 3k ? Quote Link to post Share on other sites
daniel_g Posted June 17, 2014 Share Posted June 17, 2014 Can i hear pops and bangs in there lol ?Makes me think youve an ignition related fault, dizzy cap, rotor arm something like that. Quote Link to post Share on other sites
aaddzz123 Posted June 17, 2014 Author Share Posted June 17, 2014 Yeah it revs to the limiter (Now I've fixed a million problems it came with lol)... Yes in the video it was popping and banging because someone had retarded the timing at some point. I've put it back to normal now (roughly, going to check with a timing light soon) but it's still the same... Quote Link to post Share on other sites
aaddzz123 Posted June 17, 2014 Author Share Posted June 17, 2014 Even checked this and it looks alright lol Quote Link to post Share on other sites
rasslenny Posted June 18, 2014 Share Posted June 18, 2014 holly molly u definitely went diggin deeper than i went lol.... i couldnt be bothered and bought new clocks as the scrapers had it for 10 pounds Quote Link to post Share on other sites
aidanep71 Posted June 18, 2014 Share Posted June 18, 2014 It's a variable voltage it gets I think it's goes to the ecu first not too sure on that tho Quote Link to post Share on other sites
daniel_g Posted June 18, 2014 Share Posted June 18, 2014 Yeah its pins 8 & 9 on the 26pin connector. It's a variable voltage it gets I think it's goes to the ecu first not too sure on that tho Quote Link to post Share on other sites
aaddzz123 Posted June 18, 2014 Author Share Posted June 18, 2014 (edited) holly molly u definitely went diggin deeper than i went lol.... i couldnt be bothered and bought new clocks as the scrapers had it for 10 pounds Haha . It's annoying me not knowing what's wrong. I'd rather strip down to see if I can fix it before replacing it but I think I'm going to end up replacing the tacho if it's a problem with the clocks. Hopefully most toyota from 90s era will use the same tacho as mk1 gts don't really pop up often lol. It's a variable voltage it gets I think it's goes to the ecu first not too sure on that tho Yeah its pins 8 & 9 on the 26pin connector.Cheers guys. Going to test with a multimeter later or temp wire in an external tacho to see if that works or not. Edited June 18, 2014 by aaddzz123 Quote Link to post Share on other sites
Socks Posted June 18, 2014 Share Posted June 18, 2014 If u get a meter on voltage... earth the earth probe. and put the positive probe on the RPM signal wire... You should see the voltage sweep/change as you rev the car? Best bet is to get some mk2/3 clocks butcher them and YOINK the tacho element and hope and pray its the same! Quote Link to post Share on other sites
richardc9052 Posted June 18, 2014 Share Posted June 18, 2014 Or if you want another set of mk1 clocks i know of a set for sale Quote Link to post Share on other sites
aaddzz123 Posted June 18, 2014 Author Share Posted June 18, 2014 For just £1,000,000 . Just in case how much are the clocks? Quote Link to post Share on other sites
turbo Grant Posted June 18, 2014 Share Posted June 18, 2014 Rpm signal comes from the igniter pack. Just reads the pulses off the negative side of the coil. The little connector on the side of the diag plug is the under bonnet rpm pick up. Not sure how the actual gauge works. It has a spinny thing tho Quote Link to post Share on other sites
richardc9052 Posted June 18, 2014 Share Posted June 18, 2014 £50 + postage Quote Link to post Share on other sites
aaddzz123 Posted June 18, 2014 Author Share Posted June 18, 2014 Rpm signal comes from the igniter pack. Just reads the pulses off the negative side of the coil. The little connector on the side of the diag plug is the under bonnet rpm pick up. Not sure how the actual gauge works. It has a spinny thing thoSorry dude I kinda get what you mean but can you just pin point on here where the RPM wire is please. Might have to zoom in... Or just explain a little better. Not sure if you mean a wire on the big connector or..... or I'm just not sure lol! £50 + postageI'm going to admit I'm a bit too tight to spend £50 on clocks for a working tacho haha. Quote Link to post Share on other sites
TrisK Posted June 18, 2014 Share Posted June 18, 2014 It's the ne wire on the distributer Adam. Reads the square wave Quote Link to post Share on other sites
turbo Grant Posted June 19, 2014 Share Posted June 19, 2014 The rpm wire for the tacho is a spade connector on the side of the diagnostic port with a little rubber cover over it. Quote Link to post Share on other sites
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