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Old 07-07-2006, 09:12 PM
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Tach Problems

Help!! I am pulling my hair out !! I have a 23. Pinto powered '58 Anglia. Everything was fine until I converted my dual point Mallory to Unilite. Now my tach won't read above 2200 rpm. My tach is a Sunpro Super Tach II. I used the reccommended combinations of Unilite and coil. Mallory told me that I need a tach adapter. Well, $100. later, no changes. The very vague wiring instructions say to hook up the green wire to the tach output. The unilite instructions do not desiginte a wire for tach. The orange wire to tach trigger. I hooked up the green wire to the negative side of the coil, and the orange wire to the tach feed, or wire to the tach. Anybody gone through this? I don't want to sit all weenend waiting for Mallory tach on monday. All Sunpro could tell me is that the tach need a 5 ohm square wave to work properly. Ok, no help. I am using the reccommended ballast resistor for the setup. Are ballast resistors directional? It gets pretty hot during operation. Normal?

Help!

Chris Crothers thecrow@scinternet.net

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Old 07-08-2006, 04:01 PM
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Doc here,

Sounds to me like one of a few things may have occurred..

Either the tach has gone bad from improper hookup,

(you can test by pulling a STOCK car, STOCK ignition next to yours, and run a jumper wire between the TACH output on the other car and your TACH, and a ground..Don't forget to set the cyl switch, note readings..)

Or you have the wrong TACH adapter..common on unilites..

Or You have a (Resistor??) in the wrong spot.

A resistor is a Bidirectional Device. It flows in both directions..and cuts current to a load device..

A Ballast is Traditionally installed on the + side , or 12 volts side of the coil..to reduce and buffer the amount of current used by the switching device (points or reed switch.) It allows "build" and "Decay " time across the gap, and lightens the load of the coil..resulting in the longevity of both devices.

If it is getting warm, and not on the + side, I'd say something is wrong there..

A wave shaper, is a Filter that makes a "square wave" from a non conforming wave shape produced by the trigger system on the system..Instead of a sinusoidal wave form..On a STOCK system, usually consists of a pair or resistors on series, with a pair of Caps in parallel off each resistor, to shape the wave..looks like a noise filter on a distributer or coil.

If the Tach tests not damaged, and the wiring is correct, then you have the wrong adapter.

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Old 07-08-2006, 09:06 PM
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tach problems

Hi Doc !! Thanks for the reply ! I talked to Mallory tech before buying the tach adapter. There is only 2 choices, and the one they sent is for unilite. (supposedly). I just wired the entire car. Let me give you some more info. This is a Pinto 2.3 anything but stock., in a '58 Anglia. I am using the original Pinto alternator and alternator regulator. I ran a wire from the ignition switch to one side of the ballast resistor for powerto the resistor. On that same post on the ballast resistor, I ran the wire to the "s" blade on the voltage regulator since it requires power from the iginition switch. (shortcut). Also is the wire to the unilite module power per instructions. The other side of the ballast resistor connects to the + side of the coil. Not only do I have the tach problem, but you mentioned the heat factor. The mounting bracket on the ballast resistor was extremely hot, and all the wires on the ignition side of the resistor were probably close to melting. I have wired the car with excellent grounds throughout, and everything goes back to the battery. Sunpro, says the tach need a 5 ohm square wave, and thats all the info they would give me. Since talking to you, I am more worried about the resistor heat, than the tach. I figured because of the way the resistor is built, it generated high heat normally. The charging system is working fine just for additional info. The instructions that came with the tach adapter are vague, and a little confusing to me, at best. Black to ground. Clear. Red to ignition switch. Clear. I used the ignition power side of the ballast resistor. Green to tach output on igniton system. There is no designated tach output on the unilite system, so I hooked it up to the - side of the coil. Orange, tach trigger lead. I understand this as the wire to the tach. Correct? I also, switched the green and the orange as a test, and didn't get any response from the tach at all. The tach works fine to 2200 rpm, then acts like it is hitting a needle stop. Thank you for your interest, maybe this info will help you help me. Thanks so much!

Chris Crothers thecrow@scinternet.net
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Old 07-09-2006, 04:05 PM
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Doc here,

A Ballast resistor will get hot enough to burn you .. so heat is normal..if mounted on the coil..move it..you'll shorten the life of the coil.

Test your tach on a stock system for operation before you spend any more on it..it may be shot...

normally , o a stock points system, your Tach pick up lead would be on the - side of the coil, this differs with CD or aftermarket applications..

If your using an Orange?? wire from the tach,, that does not sound right...usually the pickup wire colors are Gray, Blue, yellow, or green..you might want to check your tach wiring instructions.

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