PDA

View Full Version : Tach works when it wants...


Tdurr
12-23-2011, 05:46 PM
I looked a few different times on here for tach problems and saw one of 3 suggestions. They say it's either a dizzy going out (car doesn't misfire at all), or bad ground(not sure what ground to even look for), or a bad cluster.

Any ideas? It will sometimes work for a few hours then stop for 10min or a few days. There isn't any pattern behind it at all.
lostforawhile
12-23-2011, 05:56 PM
try swapping the coil, there is an internal resistor built into it for the tach signal, the dizzy directly fires the coil, then the resistor is between the negative terminal of the coil and the output on the blue wire
Dr_Snooz
12-23-2011, 07:52 PM
It's your ICM.
Tdurr
12-23-2011, 09:00 PM
Icm?
89T
12-23-2011, 09:49 PM
http://www.autozone.com/autozone/parts/1989-Honda-Accord/Ignition-Control-Module/_/N-ihduxZ9n80t
AccordEpicenter
12-23-2011, 11:25 PM
listen to your distributor. If it sounds like there is a small rock kicking around in it, replace the whole thing. If it sounds good change the coil
Pico
12-24-2011, 11:04 AM
the hatch was like that when I first got it, turned out to be a bad coil
Tdurr
12-24-2011, 01:18 PM
Well since it's the coil I'm just not gonna bother. Gonna be going obd1 with a internal coil hopefully by Feb so it should fix it then. :) thanks formthe quick replies tho.
Dr_Snooz
12-24-2011, 03:18 PM
My tach settled down when I replaced the ICM. I had the random tach hop though. It was working otherwise.
Buzo
12-24-2011, 04:13 PM
This is the fix for your tacho problem. A 2.2 K ohms resistor in the wires shown in the picture.

http://img706.imageshack.us/img706/5514/tachofix.png (http://imageshack.us/photo/my-images/706/tachofix.png/)
lostforawhile
12-24-2011, 05:23 PM
This is the fix for your tacho problem. A 2.2 K ohms resistor in the wires shown in the picture.

http://img706.imageshack.us/img706/5514/tachofix.png (http://imageshack.us/photo/my-images/706/tachofix.png/)

but if you do that it's going to increase the resistance to double what it should be, the internal one is part of the coil and inaccessible, I suspect it's failing due to years of heat exposure, there is a lot of heat inside of that coil
Buzo
12-29-2011, 12:39 PM
If you are concerned with the parallel resistor value, you still can cut the blue wire between the resistor and the coil terminal. But it's not needed.
lostforawhile
12-29-2011, 01:18 PM
If you are concerned with the parallel resistor value, you still can cut the blue wire between the resistor and the coil terminal. But it's not needed.

the resistor is inside of the coil. it's part of the assembly.
AccordB20A
12-29-2011, 06:21 PM
learn something every day. had no idea there was a resistor there.
Buzo
12-30-2011, 04:22 PM
the resistor is inside of the coil. it's part of the assembly.

I meant cutting the wire between the terminal B of the coil and the external resistor.

Typically this tacho signal coming out of the coil is used for signal only, so there will be almost no current draw from this wire. That's why 2.2k (with the internal coil resistor only) or 1.1k (with the parallel resistor added) doesn't matter to the tachometer in the dashboard and other devices that use this signal in the car. Also, even though I know it probes nothing, I used this parallel resistor in my car for 8 months with no issues.