GQ TD42 using standard ignition-type tacho

Hi all .. I have seen a few people asking about how to connect a tacho to their diesel, so I thought I'd share my experiences after doing a TD42 diesel conversion on my GQ.

The tacho pickup on my new engine is at the front of the engine. Im assuming its a magnetic pickup - not 100% sure yet. Some other variants have a pickup from the alternator (W-terminal) which is just a tap into one of the three phases.

I found following product online for around $70+postage. Also available on ebay. It can convert either of the above, and output to a standard ignition type Tacho.

Dakota Digital DSL-1 Adaptor

Will post more when I install it....

G'day Spektrum,

Interesting post, i look forward to your further info mate.

Please go over to the intro section bud and post up an introduction. We'd appreciate it if you could say G'day before posting further. Not a big deal but it'd be great if you told us a bit about yourself, your car and where your from.

Cheers MR

Thanks for the intro Luke, have opened this thread back up :)

Cheers

Todd

Cheers ... I hope to receive the adapter this week. Will be good to have the tacho working again!

I am going to try this

http://sites.google.com/site/rd28eng...the-tachometer

http://www.ebay.com.au/itm/chevrolet...item27c7556a1f

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Originally Posted by 97_gq_lwb

I am going to try this
http://sites.google.com/site/rd28eng...the-tachometer
http://www.ebay.com.au/itm/chevrolet...item27c7556a1f

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I think you may find there is an issue with the frequency. I have been told the TD42 sensor is 18Hz/revolution. The standard GQ ignition tach is expecting 3Hz/revolution. Therefore you will need a frequency divider to correct for this.

I hope to soon receive the adapter that I ordered. It has a configurable frequency conversion.

Have to wait and see My cluster is from the rd28 diesel gq originally and it went through the glow controller to change the tacho signal and it worked but i drowned my glow controller and decided to remove it altogether and either fit the td42 controller or a switch.
Is your cluster a td42 series 2 type i'd be interested in pics of the back of it or resistor values as they have a few options by the look of it.

Quote:

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Originally Posted by 97_gq_lwb

Have to wait and see My cluster is from the rd28 diesel gq originally and it went through the glow controller to change the tacho signal and it worked but i drowned my glow controller and decided to remove it altogether and either fit the td42 controller or a switch.
Is your cluster a td42 series 2 type i'd be interested in pics of the back of it or resistor values as they have a few options by the look of it.

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Its a TB42 cluster. I recently did a TD42 conversion, therefore the reason for the tach conversion. It's been a big job...

Ok be interesting to see if the tb cluster used the resistors and diodes in the back and what values if they did .
Theirs a pic of my cluster in this thread
http://www.nissanpatrol.com.au/forum...040#post232040

Ill see if I can get some time to check next week. Going by that photo, looks like there is 2 resistors and a zener diode. You would also need to cut the track that is currently shorting across the missing resistors. Do you have a schematic diagram? Do you know what these components are connected to? I would think they tie in with another circuit such as the tach circuit in the glow control unit.

Quote:

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Originally Posted by 97_gq_lwb

Ok be interesting to see if the tb cluster used the resistors and diodes in the back and what values if they did .
Theirs a pic of my cluster in this thread
http://www.nissanpatrol.com.au/forum...040#post232040

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I am hoping that the diodes and resistors are the difference between the td42 and rd28 clusters as in the td42 wiring diagram the tacho pulse goes direct to the cluster

Got a hold of an early td42 cluster used the tacho from it and just swapped the faces and needle over had to cut out some plastic in the back of the cluster for it to fit but it screwed straight up and does the job.

Does it connect direct to the sensor, or via another control box?

Did it have resistors/zener-diode on the back of the cluster?

Connects straight up the early one had 4 screws the bottom one was just another earth was marked d-tam on the board.
The other 3 were the same gnd ign and signal .

Where i disconnected the 2.8 glow controller i joned the yellow wire white trace to the yellow black trace wich then goes up to the cluster.
The circuit board hanging off it was a little bigger so i had to cut away some white plastic in the housing and all good .
For the needle i pushed it clock wise then kept a note of where it sat between the m and i and then fitted the other one up the same after changing the faceplate over.

Good to hear.

I received the Dakota Digital adapter today. I won't have any time to look at it until next week though.

Geez, my gq doesn't have a tacho and i was gonna put one in, didn't think too much about it till reading this. Sounds like a curly one. Might be easier to put a proxy sensor on the crank.
Does every standard TD42 patrol get the signal from the alternator? Will the wire be there or will i have to install everything from scratch?

Mine doesn't have the wire from the alternator, but you can add one (or your auto-electrician). It just connects to one of the 3 phase wires.

I hope to get some spare time to have a look at it soon....

Sorry for the delay .... rolled vehicle set my schedule behind.

Found there is a cam sensor on the TD42. Hopefully should be able to test it this week.

Got everything working .. except the tacho. The signal converter is functioning and I have a handheld tacho showing the RPM.

I pulled out the cluster, and dismantled it. I ran a signal generator into it and get nothing. It might need a pull-up resistor. Would be good to confirm if this unit was actually faulty before buying another...

Quote:

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Originally Posted by spektrum

Got everything working .. except the tacho. The signal converter is functioning and I have a handheld tacho showing the RPM.

I pulled out the cluster, and dismantled it. I ran a signal generator into it and get nothing. It might need a pull-up resistor. Would be good to confirm if this unit was actually faulty before buying another...

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Mate I don't know if its relevant to what your doing but I did find out the Patrol tacho's are quite finicky & ultra sensitive when fitting an after market HEI system.

I use a 1 watt 50k oms veritable trim pot to find its happy place. For around $2 its a very cheap testing tool for you to trouble shoot yours.

Hi Patch,

Thanks for the reply. I had thought it might just be picky about the input signal. It used to work when I had the petrol engine, but since then I have tried so many things to get it working I have no idea if I damaged the unit.

Where did you place your variable resistor? Did you place the variable resistor in series with the wire to the tacho, or as a pull-up resistor?

I noticed there is already a resistor in series with the signal (see circuit below). This resistor is positioned in the engine bay near the back of the radiator reserve, cable-tied to the ignition coil wiring loom. I tried with and without this resistor.

http://i1160.photobucket.com/albums/...tuff/Tacho.png

I just dropped the trim pot resistor in series with the signal wire. I actually removed the resistor you have marcked in your pic & used it in place of.

That resistor marked above is located only a few inches from the ignition coil in the loom heading back to the inner guard if that helps you in any way to locate for yourself.

Yeah I had already found it. I will try it tonight.

Which ignition system did you install that caused issues with the tacho? When I had the TB42, I removed the points and put in a Petronix unit. I didn't have any issues with this, but it sound like you put in something with a bit more kick.

I'm not sure why these tacho's are so picky, I would have thought the circuit would be simple ... just a frequency counter triggered by the falling edge of the signal wire. Maybe levels are not high or low enough .. or duty cycle? I need a CRO to analyse the signal from the ignition coil VS. the converter I have.

Quote:

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Originally Posted by spektrum

Yeah I had already found it. I will try it tonight.

Which ignition system did you install that caused issues with the tacho? When I had the TB42, I removed the points and put in a Petronix unit. I didn't have any issues with this, but it sound like you put in something with a bit more kick.

I'm not sure why these tacho's are so picky, I would have thought the circuit would be simple ... just a frequency counter triggered by the falling edge of the signal wire. Maybe levels are not high or low enough .. or duty cycle? I need a CRO to analyse the signal from the ignition coil VS. the converter I have.

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I used a Crane Cams multi spark CD amplifier with a mag trigger setup out of an RB30 I fabed up for the TB42 dizzy & dropped ICE ignitions leads & coil on top for good measure.

A CRO would be bloody handy just to get the signal data.... We could build a convertor of our own thats spot on for the job that way but I don't have one laying around anymore nor the bucks to just go pick one up....lol

P.s. A signal gen would go down a treat as well......hahahahahah

I have a signal generator here, but the Nissan tacho doesn't like this signal either. But my signal generator can only vary frequency and duty-cycle. It cant change the amplitude.

The diesel converter I'm using is is a Dakota Digital DSL-1. The output signal works on my handheld tach/dwell meter.
http://www.dakotadigital.com/index.c...rod/prd128.htm

It has 2 types of outputs .. standard and high voltage. The standard outputs produces a voltage pulse signal from 0 to 12 volts. The high voltage produces 6 to 18 volts -- they told me some tachometers need the extra voltage to trigger. Neither work...

I'll try the variable resistor tonight. Will be good if it works...

Quote:

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Originally Posted by spektrum

I have a signal generator here, but the Nissan tacho doesn't like this signal either. But my signal generator can only vary frequency and duty-cycle. It cant change the amplitude.

The diesel converter I'm using is is a Dakota Digital DSL-1. The output signal works on my handheld tach/dwell meter.
http://www.dakotadigital.com/index.c...rod/prd128.htm

It has 2 types of outputs .. standard and high voltage. The standard outputs produces a voltage pulse signal from 0 to 12 volts. The high voltage produces 6 to 18 volts -- they told me some tachometers need the extra voltage to trigger. Neither work...

I'll try the variable resistor tonight. Will be good if it works...

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I'd say at a guess the 18v input is for 24v systems so I hope you didn't pop yours when you gave it the extra juice.

I had been using the Normal Output for a few nights before trying the high-volt output. Hopefully by testing the High-Voltage output hasn't compounded the problem. The information that came with the unit is a bit sparse regarding the normal and high output.

Maybe it would just be easier to buy a cluster from a diesel vehicle and swap out the tach gauge.

Quote:

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Originally Posted by spektrum

I had been using the Normal Output for a few nights, and it didn't work. Hopefully by testing the High-Voltage output hasn't compounded the problem. The information that came with the unit is a bit sparse regarding the normal and high output.

Maybe it would just be easier to buy a cluster from a diesel vehicle and swap out the tach gauge.

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Yes your probably right but where is the challenge in that???........lol

That's true. Just hope I'm not wasting time with a damaged tacho gauge.

Out of interest, the petrol tach gauge is marked serial number "XP-728E". What is the serial number of the gauge for the TD42, the version that has the sensor connected directly to the gauge (not via the glow controller). "97_gq_lwb" did you see the serial number when you did the gauge change-over?

I give up. Tried everything to get this working, but it just doesn't want to work. There is every chance I have damaged the input circuitry in the tacho.

Just bought a tacho from the wreckers that suits the TD42. Will fit it later this week. Looking at the circuit diagram (TD42), there are 2 wires from the sensor direct to the tacho ... but if you look on the back of the cluster, one of them is just GND. Therefore I should be able to just ground one wire from the sensor, and connect the other to the existing loom.

All done. I picked up a diesel cluster from the wreckers, and just substituted the tach module. It's just 4 screws.

Some say that you need to run an extra wire, but that's not entirely true. There are 2 wires from the pickup sensor, but one of them is just for GND. I connected the YEL/WHT wire to GND in the engine bay, and the YEL/BLK wire goes to the existing YEL/BLK wire. This works fine.