Tach Mod Questions
Jul 21, 2014 | 12:37 PM
#21
the other option is to read up on the LM2917 chip, feed it into an arduino, and output to a servo (with the stock "guts" removed, servo + needle added in). that might at least get you a working tach
Jul 21, 2014 | 12:50 PM
#22
Registered User
Joined: Sep 2013
Posts: 70
Likes: 0
From: Mission, BC
I think it's going to work, I'm going to try pulling a singal off a coil wire (pre coil on a coil over plug engine) it'll be 12vdc and it should still function correctly, if I'm right the tach will read at about 150rpm at idle or it'll burn out the fuse, then I'll need to replace my v6 tachs 10k resistor with a 1.7k one and I should be pretty close. if it does mess with the spark i'll be ble to tell pretty quick.
Jul 21, 2014 | 03:56 PM
#24
Thread Starter
Registered User
Joined: Nov 2012
Posts: 1,165
Likes: 172
From: Tucson
I may end up getting the Dakota Digital unit for $80 - $90 if I can't find a cluster from an 88 with a 3.0.
I just haven't been too worried about it. It would be nice if I did have a working tach but I ain't losing sleep over it.
If you two rocket scientists have a way to get mine working, I'll try it.
Thanks!
I just haven't been too worried about it. It would be nice if I did have a working tach but I ain't losing sleep over it.
If you two rocket scientists have a way to get mine working, I'll try it.
Thanks!
Jul 22, 2014 | 07:30 AM
#27
Registered User
Joined: Mar 2014
Posts: 29
Likes: 1
Have you looked at 87-88 gauge cluster on car-part.com? I would imagine all of the gauges should be interchangeable, I've used a combination of parts from 3 clusters for mine. You might have to move some of the wires in the plugs around, I think they vary from year to year.
I got my tach working in my 88 4runner (originally 22RE).
I got my tach working in my 88 4runner (originally 22RE).
Jul 25, 2014 | 08:39 AM
#28
Registered User
Joined: Sep 2013
Posts: 70
Likes: 0
From: Mission, BC
Right now my cluster has got the 3 VSS wires the coolant temp sender oil pressure sender and tach singal wire pluged into the harness and nothing else, The oil, temp, fuel and volt guages all wokr, dummmy lights still seem to work but still no speedo or tach.
what I'm thinking is there's some power wires feeding the combo meter (maybe the fat w//r wire?) that I don't have hooked up but I can't find the pinout digram I need to figure it out, anyone got any info on this?
what I'm thinking is there's some power wires feeding the combo meter (maybe the fat w//r wire?) that I don't have hooked up but I can't find the pinout digram I need to figure it out, anyone got any info on this?
Jul 20, 2018 | 02:45 PM
#29
Registered User
Joined: Aug 2014
Posts: 18
Likes: 0
From: King Co Washington
If you have your tach loose then take a look at the circut board and find the resitor you're suposed to parralel or replace, it should be located after the frequency to voltage converter in the circut somwhere, get the resistance rating.
The tach is a simple frequency to voltage converter, it takes a pulse and makes a voltage value out of that frequency, the coil then tightens and loosens depending on the amount of voltage going through it moving the needle, if yours isnt moving at all with the tach wire connected to the body harness in the right spot then it's not an analog signal or it's not the right wire, hooked up you should be reading a value 1/4 of what you should be geting.
Next is the maths. in you're case a single coil on 4 cylinders = 2 pulses per rev for the cluster (a coil fires every 4 strokes so once per 2 revs/4 = 2) the coil per plug will be 1 per 2 revs so you need to reduce you're resistance by 4 in order to multiply your voltage by 4 (a 10k resister would need to be replaced by a 2.5k resistor) that should get it to read correctly provided your drawing your tach singal from the correct spot, this I can't help you with I don't know much about the 3.4l.
I imagine they were analog up in to the late 90's then witched to digital when the ignition becomes computer controlled (coil over plug). A digital tach signal is not going to help you turn that old cluster it needs to be analog.
There are some options here, I'm wokring on figuring out where I can take an analog signal from an entirely digital engine right now.
The tach is a simple frequency to voltage converter, it takes a pulse and makes a voltage value out of that frequency, the coil then tightens and loosens depending on the amount of voltage going through it moving the needle, if yours isnt moving at all with the tach wire connected to the body harness in the right spot then it's not an analog signal or it's not the right wire, hooked up you should be reading a value 1/4 of what you should be geting.
Next is the maths. in you're case a single coil on 4 cylinders = 2 pulses per rev for the cluster (a coil fires every 4 strokes so once per 2 revs/4 = 2) the coil per plug will be 1 per 2 revs so you need to reduce you're resistance by 4 in order to multiply your voltage by 4 (a 10k resister would need to be replaced by a 2.5k resistor) that should get it to read correctly provided your drawing your tach singal from the correct spot, this I can't help you with I don't know much about the 3.4l.
I imagine they were analog up in to the late 90's then witched to digital when the ignition becomes computer controlled (coil over plug). A digital tach signal is not going to help you turn that old cluster it needs to be analog.
There are some options here, I'm wokring on figuring out where I can take an analog signal from an entirely digital engine right now.
Thread
Thread Starter
Forum
Replies
Last Post
