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Hi everyone,
I purchased a 2" diameter ISSPRO tachometer (GAUG_08.1_322) from MMI earlier this year. I finally got around to installing it last month on my late model A4 as per the accompanying wiring diagram. Since this is a marine application, I used dielectric grease on each connection to avoid corrosion. It worked fine the first time I started her up. However, I went back to the boat on July 4th and discovered the tachometer needle pegs at 4000 RPM as soon as the ignition switch is turned on. That is, BEFORE the starter is actually cranked. After the engine starts, the needle remains pegged...at idle or at any speed. How odd.
I checked my wiring connections. All connections are tight and verified from the wiring diagram that everything was wired properly. I verified the jumper on the back of the tachomeer was intact and set up for a 4 cylinder engine.
Then I disconnected each of the three wires (one at a time) to try isolating the problem. When I disconnected the (white wire) from the negative terminal of the coil the needle remained pegged--No impact! Hmmm.....Then I reattached it. When I disconnected the red power wire from the ignition switch the needle flat lined. Then I reattached that wire. When I disconnected the black (ground wire) the needle flat lined, so I reattached the black wire to the ground. Thinking the wire between the negative post of the coil and the white wire on the tachometer had a short, I finally replaced this wire...Again the needle pegged as before.
BTW, I am using a Pertronix epoxy-filled Flame Thrower coil (model 40611). I have no external resistor installed.
I am starting to suspect I have a defective tachometer. Before I jump to such conclusions, does anybody have any idea what the problem would be? Thanks in advance.
I purchased a 2" diameter ISSPRO tachometer (GAUG_08.1_322) from MMI earlier this year. I finally got around to installing it last month on my late model A4 as per the accompanying wiring diagram. Since this is a marine application, I used dielectric grease on each connection to avoid corrosion. It worked fine the first time I started her up. However, I went back to the boat on July 4th and discovered the tachometer needle pegs at 4000 RPM as soon as the ignition switch is turned on. That is, BEFORE the starter is actually cranked. After the engine starts, the needle remains pegged...at idle or at any speed. How odd.
I checked my wiring connections. All connections are tight and verified from the wiring diagram that everything was wired properly. I verified the jumper on the back of the tachomeer was intact and set up for a 4 cylinder engine.
Then I disconnected each of the three wires (one at a time) to try isolating the problem. When I disconnected the (white wire) from the negative terminal of the coil the needle remained pegged--No impact! Hmmm.....Then I reattached it. When I disconnected the red power wire from the ignition switch the needle flat lined. Then I reattached that wire. When I disconnected the black (ground wire) the needle flat lined, so I reattached the black wire to the ground. Thinking the wire between the negative post of the coil and the white wire on the tachometer had a short, I finally replaced this wire...Again the needle pegged as before.
BTW, I am using a Pertronix epoxy-filled Flame Thrower coil (model 40611). I have no external resistor installed.
I am starting to suspect I have a defective tachometer. Before I jump to such conclusions, does anybody have any idea what the problem would be? Thanks in advance.
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