electrical testing of cluster and gauges..

[Miranthis]

Anyone have idea for a good desktop 12v power supply that is NOT a 12v acid battery on my desk over the carpet. I'd like to do some bench testing of gauges etc. Ideally, I'd like to test the tach, but that would involve replicating the output signal of the "tuna can". Anyone know what that signal looks like? The input to the can is from the coil, so pulsed, but does the tuna can convert the pulse to a proportional voltage, or does the tach gauge itself get a pulsed signal. The tach itself looks like it has minimal brains and the circuitry is primarily in the tuna can.

 

[67Dart273]

There are all kinds and amperage outputs of power supplies. Sometimes you can find adequate "wall worts" in thrift stores, but you have to have some idea of the amperage you need.

Some tachs you can test with a trigger from a pulse signal generator, and you can buy some of them, "china" from egag.

However, some of the early Mopar tachs are weird. Without a diagram, component values, or one to play with, I have no idea.

Of course we have no idea what you are working on, because you failed to mention that

 

[Miranthis]

for the moment I am using M12 Fuel batteries out of my Milwaukee tool set....

 

[67Dart273]

You haven't told us ANYTHING about what you are working on. So far as I know, the older tachs --the ones that used a sender---were just a meter and all the electronics were in the sender. This would be similar to taking, say a Sun or Rac or any other tach apart and separating the circuit board (sender) from the meter (two wires)

 

[Miranthis]

Primarily I am checking function on the gas, oil and temp gauges. I will be doing the RTE solid state voltage Limiter to feed the gauges, but for now I am just bench testing to see what of my collection of wayward gauges works and what does not. I am also rebuilding some original gas tank sending units and to test function it was useful to have the gas gauge set up so I could adjust the nonlinear resistor in the sending unit and confirm function.

As for the Tach tuna can sending units, I do have a few originals with my pair of original tachs, but will be using the replacement circuit boards for those as I am going to electronic ignition. So I am not actively doing that testing at the moment. It is harder to replicate that signal on the benchtop anyway.

 

[Mike69cuda]

Computer power supplies make great 12v and 5 volt supplies. They are dirt cheap used.
All you need is to add a switch. Plenty of instructions on the web on how to do it.

 

[harrisonm]

A lot of our gauges (at least the ones on my 69 Barracuda) run on a pulsing 5 volt power source from the IVR (instrument voltage regulator). The one in my car is built into the gas gauge. When I restored the car for the first time about 35 years ago, I had a lot of electrical problems to solve. And this was before the internet, so I had to figure a lot of it out on my own. I test gauges with 3 AA batteries laid end to end yielding about 4.5 volts. I wrote a rather extensive article on diagnosing and fixing electrical problems and presented it to Mopar Muscle Magazine about 24 years ago. They liked it and printed it in three parts. I will find my copy and get you the section on testing instruments.

 

[Miranthis]

A lot of our gauges (at least the ones on my 69 Barracuda) run on a pulsing 5 volt power source from the IVR (instrument voltage regulator). The one in my car is built into the gas gauge. When I restored the car for the first time about 35 years ago, I had a lot of electrical problems to solve. And this was before the internet, so I had to figure a lot of it out on my own. I test gauges with 3 AA batteries laid end to end yielding about 4.5 volts. I wrote a rather extensive article on diagnosing and fixing electrical problems and presented it to Mopar Muscle Magazine about 24 years ago. They liked it and printed it in three parts. I will find my copy and get you the section on testing instruments.

Thanks. I am running 12vDC through the 66 gas gauge and getting the essentially irregular AC voltage of about 3 ish V out. I will try the AA batteries. Learning my way through rehabing the electrical and going to convert to the RTE IVR unit and do some other upgrades (HL relay etc.), as my original bulkhead connector and thr HL switch both had overheating and melting. I kinda want the ammeter to work though, so taking things off the main circuit with a relay is a downside. Hoping that going to LED headlights will lower the running amperage enough to help, although new wiring harnesses will undoubtedly be a great start.

 

[RedFish]

I have a power supply from a PC tower I built years ago. I get 5V, 9V, 12V. Just added a little jumper to make it come alike with its own on/off switch. I recall yellow is 12V and red is 5V which is opposite my IVR color scheme.

 

[Mike69cuda]

I made a sender tester out of some resistors I use to troubleshoot gauge issues. If you want to borrow it, I’ll send it to you. Just send it back when you are done.

 

[RedFish]

A decade resistance box is around 25 bucks at Amazon. May be Chinese but gets the job done and yours to keep. Cheers

 

[4spdragtop]

Nicely done! I would assume good for testing a few different gauges?

I made a sender tester out of some resistors I use to troubleshoot gauge issues. If you want to borrow it, I’ll send it to you. Just send it back when you are done.

View attachment 1716450190

 

[Mike69cuda]

Yep, works for temp, gas & oil. Not perfect but good for checking basic gauge operation.

 

[67Dart273]

So you finally admitted that you are working on a 66, is that right?

If you actually want the ammeter to "work" you need to think hard about what you are doing, because the original circuits ARE NOT ADEQUATE at all, when adding more electrical loads and or higher output alternators. There is no reason to re-invent the wheel. There are tons of threads on this subject.

"In theory" if you were to upgrade the wiring BUT NOT THROUGH the original bulkhead connector, you could add a SHUNT around the original ammeter, perhaps aided with diodes, to provides sort of a "scaled" shunt.

ARE YOU AWARE of what is called fleet/ police/ taxi alternator wiring? Look that up. Go to MyMopar and download about 70-72 service manuals and you'll find it in those maybe in the B bodies. This was a "partial" bypass of the bulkhead connector but which still left the ammeter in use.

 

[jeff alder]

Anyone have idea for a good desktop 12v power supply that is NOT a 12v acid battery on my desk over the carpet. I'd like to do some bench testing of gauges etc. Ideally, I'd like to test the tach, but that would involve replicating the output signal of the "tuna can". Anyone know what that signal looks like? The input to the can is from the coil, so pulsed, but does the tuna can convert the pulse to a proportional voltage, or does the tach gauge itself get a pulsed signal. The tach itself looks like it has minimal brains and the circuitry is primarily in the tuna can.

 

[Miranthis]

View attachment 1716450228

Well, as it happens i have several HO train control boxes with my granddad's old HO trains. See THIS is why i like you guys. I mean any of us COULD just pay someone to do all the car stuff for us, but where is the fun in that.

 

[Miranthis]

I made a sender tester out of some resistors I use to troubleshoot gauge issues. If you want to borrow it, I’ll send it to you. Just send it back when you are done.

Mike, I am in KC Metro as well, as I live on KS side and work in Lee's Summit. No need to send it, as I can just meet you. Will DM you...

 

[Miranthis]

So you finally admitted that you are working on a 66, is that right?

Why yes, I AM a 66 Barracuda guy...you make it sound so scandalous ( ) , but that is what I am, a 66 Barracuda guy, as my tagline in all my messages says.

Seriously, thought, thanks for the Great info and I will be looking at it. I am aware of the shunting of the higher current stuff away from the ammeter as I had to have that done on a 67 Coronet 500 when the ammeter shorted while I was driving it back in the 80's. I understood the necessity but always missed the ammeter.

 

[67Dart273]

A train transformer may be a poor choice because I've never seen one with any filtering. BUT YOU CAN ADD a filter. Just look at the highest V output rated on the label, AKA 28V or whatever, and then buy an electrolytic filter cap with some voltage headroom. I'd use 50V Value is not terribly important. Perhaps 1000uf, even 500uf might be enough. Digikey and Mouser, last I knew, would sell small orders. Then there's ebay. There's also a handful of guitar amp// vintage radio repair websites that will supply small orders.

CAVEAT. MONITOR THE OUTPUT voltage closely as you do NOT want to overvolt the gauges. If you are feeding the IVR in the cluster, you want 12.6--14V. If you are not using an IVR and feeding the gauges directly, you want 5V no more than 6

If this is a Rallye cluster, with the built in IVR, you want to disable it. Go to the RTE site for some info. You can "goop" or RTV the contacts in the built in IVR so they do not close.

 

[67Dart273]

I've had a housefire, and just about anything I do has come to a halt. But I had started trying to experiment with the idea of replacing the old "full current" ammeter with a newer "external shunt" one. I scored one out of some unknown Ford, as well as a 76 A body, which were used either 75, or 75 and 76. Ma also used external shunt meters clear back in some of the "cee" barges in about 72.

 

[RedFish]

You don't need to open the fuel gauge unless you wish to have a look inside. To bypass the built in mechanical limiter and supliment it outside the fuel gauge, simply lift the fuel gauge from the cast housing and interrupt its chassis ground path. Leaves it in the dark. Take the 12V wire (blue with white tracer) to wherever the supliment regulator is placed.

 

[harrisonm]

Anyone have idea for a good desktop 12v power supply that is NOT a 12v acid battery on my desk over the carpet. I'd like to do some bench testing of gauges etc. Ideally, I'd like to test the tach, but that would involve replicating the output signal of the "tuna can". Anyone know what that signal looks like? The input to the can is from the coil, so pulsed, but does the tuna can convert the pulse to a proportional voltage, or does the tach gauge itself get a pulsed signal. The tach itself looks like it has minimal brains and the circuitry is primarily in the tuna can.

Here are some pictures of the third installment of the electric article I wrote for Mopar Muscle. If you need better pictures, PM me.
Mike

 

[RedFish]

First time I saw the "bend the thingy" published it was from Rick Erinburg (spelled) at a Imperial website. Everyone who has internet (including Real Time Engineering) has simply propagated this BS. I will leave this life still wondering if I was the first to take a good look for a chassis ground at this gauge can. Here's a clue,,, have a look at a the OEM external limiter. I has 3 connections, 12V in, low V out, and chassis ground. There's your sign.