Tested Gauge Clusters

Because of the amount of threads about faulty gauges, lately, I am toying with the idea of buying some GQ gauge clusters and testing/repairing and selling them on an exchange basis on the forum, to trusted members. This would not be a full on business but more of a hobby, to start with. If it is successful, I am thinking of also doing the more technically advanced GU clusters. I have been interested in buying a good oscilloscope and signal generator for a long time, and this is a good reason to do so. To get started, I would need some help to get readings such as differing voltage inputs etc. And even average speed sensor readings for different tyre sizes. I would also need opinions on how much members would shell out for a tested cluster. The exchange would only work if everyone promptly returns their cluster and also I need to find replacement parts. Postage to my location may be a prohibitive cost too. This is only a pie in the sky idea at the moment, but let me know what you think. If I cant find original parts, I might have to retro fit after market ones.

Any interest at all?

I was wondering if there was a test sequences for them.. Ie x voltage is half tank, or high oil pressure.

Is there such a thing coz I'd like to test mine to eliminate it from my issues..

On the early model gauges, most of the input signals can be replicated by a simple voltage and variable resistor and the gauges tested with a multimeter. I want to view, (on an oscilloscope), the average inputs for the tacho and speedos and use a signal generator to produce almost the exact inputs for accurate measurement.

Most of them are rated at FSD at a certain current. All you would need to do is build yourself a variable constant current source (using a 7805 or such) and then get the gauge specs. Some gauges have the FSD spec written on them.

I have the guts out of a few different power supplies left over from some other jobs, so it won't be a problem to build one to test Full scale deflection. But I would like to get some wiring looms and make a plug 'n' play unit. And the "Dearest, I need a an oscilloscope and signal generator" factor is at play here too.:)

You won't need much of a signal generator as it would need to be more of a pulse generator. Again a simple kit from Jaycar would do the job. The CRO would also need to be fairly basic as you would not need one with a high frequency response or a large bandwidth. You are mainly looking at pulses at low frequencies.

I have done a bit of research and found some basic gear for reasonable prices. Brand new portable LCD oscilloscopes have come a long way since the CRO. I have even found one that has an in built sig gen. I also wish to get back into electronics, which has changed so much since the days of my apprenticeship, in the eighties. I have been shopping around for a small second hand metal lathe as well, so I can have the option of fully reconditioning alternator slip rings.

Drop cuppa a pm incase he has missed this thread as I know his cluster was playing up.

I'll pm him now, thanks.

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Originally Posted by megatexture

........I know his cluster was playing up.

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He has serious problems.........but, how did you find out??

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Originally Posted by geoffayres

He has serious problems.........but, how did you find out??

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Oi, don’t tell everyone ..... it’s personal! :tease:

Seriously though ..... the problem was fixed....... with a little help from my friends & an extra strap.

@mudnut, a bloke is splitting a gq in Portland.I'll get his number to you if you like.

But if you do something soon I'd like mine tested..

Mudnut, Do you have a spare GQ instrument cluster or do you know if there is a voltage regulator on the supply feed to the gauges?

I don't think there is but I'm not 100% sure.

Wow, blokes the Questions are coming thick and fast now! I have spent the last couple of hours researching equipment and variable resistors.

Yes, please, Kallen. PM me his number. I have the cluster, out of my 4wd corolla to do some initial tests on as a guide to what components I will need to replicate gauge readings etc. Finding cheap variable resistors with a good wattage rating is proving to be fun. I may have to parallel some double gangers to cope, so I should get something going in the next few weeks. In the Haynes manual I have, there are some simple tests for the gauges.


Yendor, I haven't got a cluster, but hope to have one soon. I'm hoping all of the Q clusters have the same connectors even though Diesel and petrol models differ. I will scour the manuals and see if there is some sort VR in the circuit.

Edit. The electronic manual shows three different gauge clusters, with the what looks like identical sockets.

Yendor, so far all I have found is the resistor circuit in parallel with the speedo and voltmeter and then in series with warning lamps. This would act a a basic regulator. I suppose they rely on the alternator VR. Please correct me if I am wrong.

I am having trouble finding the expected voltage readings for the tacho in the three manuals I have. I am a bit averse to testing across the terminals with my moving coil meter. An auto elec warned me off doing that many moons ago, but I can't, for the life of me remember the reason behind it.

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Originally Posted by mudnut

Yendor, so far all I have found is the resistor circuit in parallel with the speedo and voltmeter and then in series with warning lamps. This would act a a basic regulator. I suppose they rely on the alternator VR. Please correct me if I am wrong.

I am having trouble finding the expected voltage readings for the tacho in the three manuals I have. I am a bit averse to testing across the terminals with my moving coil meter. An auto elec warned me off doing that many moons ago, but I can't, for the life of me remember the reason behind it.

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I didn't think they did have a VR mounted in the instrument cluster.

I'm just thinking if there was, then this is what might be wrong with Kallen's.

A digital multimeter will be fine to use or even better a new scope :wink:

I remember seeing someone posted scope reading, I think for engine RPM and vehicle speed. It was awhile ago......I will see if I can find it later tonight.

What price would everyone expect to pay for a secondhand cluster and partial wiring loom?

Digital meters have a much higher input impedance than moving coil meters (Meg ohms as opposed to kilo ohms in some cases). This means that when you poke a digital meter into a circuit - the meter does not have an effect on the circuit operation (ie the meter does not change the overall resistance of the circuit). Moving coil meters due to their lower input impedance (especially the cheap ones) can do anything from changing the characteristics of a circuit and giving you incorrect readings to adversley affecting a circuit and stopping it from working or even damaging the circut.

I have a cheap digital multi meter, but it likes to give odd readings sometimes, so the "Dearest, I need a good digital meter too" will come into play when I let her read your post.

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Originally Posted by mudnut

I have a cheap digital multi meter, but it likes to give odd readings sometimes, so the "Dearest, I need a good digital meter too" will come into play when I let her read your post.

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You can get very reasonable digital meters for around $40. Not so many years ago they were many hundreds of dollars - but not any more. Some years ago the average price for our work meters was just under the $1000 mark. Jaycar have a good range of good quality reasonably priced meters. Don't buy a $10 meter. May be OK for an emergency meter in the boot of the car - but not for any serious measurements.

One other point when buying a meter - make sure it measures amps in the micro amp range. Some of the current measurements you will be making will be very small. If you buy a meter suitable for an electrician to use you will find they don't measure very small currents. You will need a meter suitable for an electronics tech.

I remember seeing some lcd screen type meters, by fluke which I think have oscilloscopes in built, if I read the description correctly. I skipped over them thinking that they would be very expensive. I will have another look as someone might make a generic model.

Pm sent bud

Thanks, Kallen, I'll get onto him this week, hopefully.

Heres that link mate

http://www.patrol4x4.com/forum/nissa...e-width-97071/

That is excellent reading thanks, Yendor. It gives me a starting point. The Q that Kallen put me onto is a TB42 E, so I will have a common gauge to start with, I will see on Monday, what else I can score from the wreck.

I have got the gauge cluster, blinker and light control assembly, hand throttle and windscreen wiper motor for $50 so I am pretty happy. It was a lwb so all the doors, which looked ok are for sale. The engine is gone, but the auto is still there. The dash looks reasonable too. The clear face of the cluster was cloudy, but I have spent some time polishing it. I want to use armour all on it, but I am wondering if it may go cloudy like some commodores do. Any thoughts?

Some initial readings on the gauge cluster plug and play test unit.

The whole dash cluster only uses 1.5 to 2.5 amps with all lamps lit (-ve switched lights. Lamp test and +ve switched lights).

My battery drill only gets the speed sender unit up to 60 kph.

I will have a dig in the shed and find another small variable speed motor to run the unit, until I get a signal generator which will do the tacho input as well.

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Originally Posted by mudnut

Some initial readings on the gauge cluster plug and play test unit.

The whole dash cluster only uses 1.5 to 2.5 amps with all lamps lit (-ve switched lights. Lamp test and +ve switched lights).

My battery drill only gets the speed sender unit up to 60 kph.

I will have a dig in the shed and find another small variable speed motor to run the unit, until I get a signal generator which will do the tacho input as well.

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Huh. My spedo is electronic to the cluster. Or did you strip that ti??

I took the sender off my knackered gearbox, just to see the wave form, current and voltage it produces. I just connected a bit of tough rubber tube between the sender drive shaft and a bit of a bolt in the drills chuck. It works a treat.

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Originally Posted by mudnut

I took the sender off my knackered gearbox, just to see the wave form, current and voltage it produces. I just connected a bit of tough rubber tube between the sender drive shaft and a bit of a bolt in the drills chuck. It works a treat.

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Usually simple = good. Why make it complicated?

This is the Plug and play gauge cluster test 'bench'. (Don't look at the failed paint job) The speedo signal is at 175 Hz at 60 kph. The power supply drops to 11.9 volts when the cluster is powered up, so this reading isn't accurate. I have to pull the supply apart and check it out. It needs a better voltage regulator and a couple of capacitors fitted to lift it to 13.8 Volts under load. The trip meter and odometer also clocked up 4 ks during the test so that was a bonus.

The readings on the road for 60 kph with Mrs mudsane driving were 170 hz. Which is very close to the stationary test I did yesterday, but could be her interpretation of what position the needle is at 60.

Anything below 50 was unreadable, but that may have been the way I had set up the oscilloscope.

I tried the scope on my tacho input, but it showed a 9v bias with a minute square wave on the very top. Again, it is probably the way I interpreted the Chinese instructions. I will talk to a mate who does Dyno tuning and get his opinion on what signal to expect.

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Originally Posted by mudnut

I tried the scope on my tacho input, but it showed a 9v bias with a minute square wave on the very top. Again, it is probably the way I interpreted the Chinese instructions. I will talk to a mate who does Dyno tuning and get his opinion on what signal to expect.

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Set the scope to AC coupling. Then turn up the vertical amplitude.

Thanks, The "toy" only has DC coupling. I have been trying to learn to navigate the device. I have posted the link to the instruction manual in the multimeter thread.

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Originally Posted by mudnut

Thanks, The "toy" only has DC coupling. I have been trying to learn to navigate the device. I have posted the link to the instruction manual in the multimeter thread.

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OK - I have used many scopes and never heard of one without AC coupling. You live and learn.

http://www.ebay.com.au/itm/291039883...84.m1423.l2649

@ Mudnut this any good for you

Thanks for finding that meter, TD, I have a Jaycar QM1551 meter. You have reminded me to take it back, as the the duty cycle mode is unable to measure square waves correctly.

To date, I have had trouble finding information regarding the test procedures on tachometers. I took the plug'n'play test bench to a retired electronics tech's place and spent the afternoon running tests and recording results. He is going to draw up a circuit that will amplify the test signal produced by the Oscilloscope. it should be an easy build, which I am looking forward to. And because I'm too tight to pay out for a portable 12v sig gen, I will use a small variable speed 12v motor I have found in the shed, to run the speedo sender up to 110 kph.