Tach for CUCV

m4A1

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Does anyone know how the lug on back of the Alt #1 determines the rpm? I heard it is where the STE/ICE picks up the rpm and was wondering is there a way to rig a tack with it?
 

Westech

CPL
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cow farts, Wisconsin
yes you can buy Diesel tachs. JC Whitney has them also do a search on the web about them. They hook up right were you stated, you program it to your truck. Really ez.
 

dunedigger

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Hart, MI
I thought awhile back I noticed a wire to the diagnostic plug for a tach read in the tm manual. I remember wondering if it could be taped off that wire but I didn't look into it any farther.
 

rockspider

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Is it that single brown wire, that has a rubber covered round female plug?
If I buy a diesel tach, do I have to splice that wire for the tach, or can i remove the original one and wire only the tach?
Is it necessary to keep the brown wire connected? Or was it connected to the diagnostic plug (which is missing), meaning it isn't in use anymore??
 

mangus580

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The CUCV actually has some sort of conversion circuit for the tach wire in the diagnostic plug. I had at one point meant to dig out an old tach, and attempt to connect it to that wire... and see what happens.

I would have to imagine, that they converted the signal to something pretty standard, in order to work with the STE-ICE unit... otherwise, the would have had to convert EVERY vehicle to all be the same.

Anyone have a sacrificial tach they wanna try??
 

rockspider

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I asked same info to an electrician workshop, he is very optimistic and told me to not worry, whichever diesel tach I'm going to buy aftermarket, chances are it will work from that small brown wire post, or he can open the alt and just pick one of the phases signal and make the tach work with that.

If so, should be really simple.

Time to shopping for a tach then! :-D
 

mangus580

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Diesel tachs are usually a lower RPM range to start with....

The also either use a magnetic pickup, mechanical (cable) or an alternator wire.
 

allrevup

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Location
Delaware
I have a photo of a M1028 (sorry,not clear enough to scan and post) that was on ebay about 2 years ago in the Annapolis,Md. area. This one had a Tach. and a hour meter, mounted over were the radio delete plastic plate is. A flat black metal plate angle towards the driver 8* x 4 1/2", with a 3-3 1/2" VDO (300-40 100ths. RPM tach.) and a 2" ( +/- )VDO quarts hour meter set towards the lower right, the plate is held in place by two screws at the top corners on to the dash bessel. Under this (above and to the left of the STE- ICE plug) there is a triangular plate with a rubberize push botton and just below that what appears to be a iddle speed control lever. The guy that had this for sale said that she was original UNCLE SAM and looked very correct with only 419hrs. Anyone knows what this ad on kit, may be? The correct instalation manual would explain how to ad a tach.
 
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truck0590

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Manassas, VA
I thought I remembered somewhere that you could replace the vacuum pump with a driver for a tach - maybe off HUMVEE 6.2s. This is a very vague recollection.

Truck
 

allrevup

Member
270
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Location
Delaware
found it. this is what I was told to be a optional equipment tach./hr. meter equiped M1028A1 (Sorry for the bad resolution, but this is a a photo of a bad photo) Question? if you use a Humvee tach. drive in place of the vacum pump, then what do you do for a vacum source? I am not familiar with the Humvee set up. Thanks
 

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allrevup

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I have yet to find so much as a refference to this set up. Would love to find a kit as well...not difficult to favricate I even found the equivalent VDO parts(for industrial and marine) and I guess the pick up point would be one of the already mention in the tred. But exatlly HOW did the MIL.GOV did it?
 
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ragedracer

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Found this over at ck5.com...

Ok, uber writeup time! First things first, a BIG thanks to Lee Swanger from www.thedieselpage.com for coming up with the circuit, I had no part in developing this one myself :)

Now, I know most of you are going to take one look at this circuit and look a bit like this -> but it is actually a pretty simple concept.

First things first, I should explain what exactly a transistor is. A transistor is basically two diodes connected together. Diodes are basically one way check valves for electrical current. They flow current like a bare wire in one direction, but allow very little current to flow through in the other direction. When you put the diode in so current flows through it, it is said to be forward biased, when it blocks flow, it is said to be reverse biased.

One side of the diode is called the cathode, and the other is called the anode, but when it comes to transistors, the cathode is the "N" junction, and the anode is the "P" junction. Depending on how the diodes are mated together in the transistor is called either a PNP or NPN transistor. The only difference is if the cathodes are connected together (PNP) or if the anodes are connected together (NPN).

Every transistor has three poles on it, one is called the collector, another the emitter and the third is the base. The collector and emitter are the ends of the diodes that are not connected together, and the base is the terminal that is attached to the connection between the other two ends of the diodes.

I won't get into why or how, but a transistor is capable of being in three basic modes. One is called cutoff, another is called saturation, and the third is called the active mode. When you operate a transistor in saturation or cutoff mode, it operates just like a switch, either allowing current to pass, or not(I'll let you guess which mode is which). When it is in active mode the transistor acts as an amplifier and increases the size of the input signal.

Now, since the stock engines speed sensor outputs the triangular looking signal, we want a way to clip the signal and convert it into a square wave which most gasoline tachometers use. To do this, we want to have some way to make the transistor output a 9 - 14 volt square signal when the sawtooth waveform is at one point in its cycle, and make it into a 0 volt signal at another point in it's cycle. What we do to pull this off is use the transistor as a tiny relay that is either on or off depending on the input signal.

Since I have not looked at the ESS signal on an oscillioscope myself, I can't say for sure exactly where in the signal the change happens, but what you see below should be accurate enough for our purposes.

Basically, when the sawtooth waveform goes positive, the base is given enough current to put the transistor into saturation, which closes the circuit and allows power to pass into the tachometer. When the sawtooth waveform goes negative, it opens the circuit and provides the sudden loss of voltage that the tachometer is looking for. Becuase the transistor is switched on at a certain point, the voltage of the input signal doesn't make any difference to the circuit's operation, just the frequency. Since the transistor is switching full battery power on and off, the tachometer gets the proper square wave signal it is looking for and displays the approriate engines speed based on that signal.

The resistor sizing changes how the transistor behaves, and when it will go into saturation / cutoff essentially setting conditioning the circuit to work with your V8 tachometer. The capacitator is used to clean the signal up for conversions so you can eliminate any spikes in ESS signal that could put the transistor into the wrong mode and make the tachometer read incorrectly.

If that made no sense, don't worry about it, just hook the circuit up the way you see it and enjoy! If you understand this stuff, and I made no sense, I apologize, just learned how to do this stuff a couple weeks ago at school
 

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jakwi

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Colorado Springs
Found this over at ck5.com...
Has anyone ever figured this out? The diagram for this circuit refers to the california ESS signal for the sawtooth waveform. Does the J code 6.2 have a similar device? Has any one ever looked at pin E (the tach pin) on the ste/ice diag plug to see what is actually there?

I would really like to use this old tach I have and make this work. That little circuit would cost next to nothing to put together.
 

motormayhem

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Location
Tucson, AZ
Has anyone ever figured this out? The diagram for this circuit refers to the california ESS signal for the sawtooth waveform. Does the J code 6.2 have a similar device? Has any one ever looked at pin E (the tach pin) on the ste/ice diag plug to see what is actually there?

I would really like to use this old tach I have and make this work. That little circuit would cost next to nothing to put together.
I hooked a multimeter up to mine and nothing showed. Not sure if it is not going to show anything or if mine is dead.

I too am interested in working it so I could add a tach for under $50 or use a gas one I have laying around.
 
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