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Tach not working


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I converted my cluster form idiot lights to gauges with the kit sold by sonnie24 on ebay I have seen others use the kit with success. When I first cranked the car fot the first time the tach went up and down from 300 to 500 or so but when it finally started it was reading 0 now the tach will not move at all. I did some research and found some things about a tach filter when using a hei distributor (i have a summit brand hei distributor) but they all had a tach that read just bouncing around or wont go over a certain rpm. Im pretty much lost at this point. I have doubchecked all connection, I have made and made sure the ground wires behind the dash are connected all other gauges and dash lights working properly any help would be appreciated.

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Congratulations on making the conversion to a full gauge dash, Evan! From personal experience with this conversion, I think/hope your current tach problem will be fairly easy to diagnose and fix.


I have reviewed the detailed instructions that Darren and I put together and will offer the following for your consideration:


1. Since all of the other gauges and dash lights appear to be working, the grounds to the dash frame, headlight switch and circuit panel must all be good (as you have already verified).


2. Since the needle of the tach initially moved, there was at least a temporary signal that got to the gauge (although that circuit is possibly faulty or completely open now).


3. Since the tach is now not working at all, and the other gauges and lights still work, I can think of three possibilities for the source of your problem:


First, it may be a filter problem but, as you suggest, since the tach is now not working at all, it is more likely a faulty signal circuit. I did not install an HEI filter and my tach appears to work fine, but it might be the easiest thing to try first.


Second, the tach you got in your kit may be defective and will need to be returned/exchanged. This, however, I seriously doubt and would only go down that path if all other possible sources of the problem have been conclusively eliminated.


Third, I suspect that the signal circuit to your tach is faulty/open, giving either an intermittent or total failure. I would do a complete verification of the signal circuit from one end to the other. You may have already done some or all of the following, but I will list them since I don't know:


The signal wire for your new in-dash tach is the brown wire that came in the kit. It runs directly from your HEI, through the firewall, to the big plug on the back of the instrument cluster. Thankfully, it does not go to or through the fuse panel plug so you don't have to mess with that.


If you start at the HEI tach connector, be sure you are connecting the brown tach signal wire to the correct downward pointing blade on the driver's side of the HEI and that the connector is firmly and completely pushed onto the blade. The female connector that came on the brown wire in my conversion kit was an extremely tight fit to my HEI tach port connector.


If the tach still doesn't work, I would verify the connector-to-connector continuity of the brown wire. Also, since you had to run the brown wire through some new or existing hole (with a rubber grommet) in the firewall, be sure it is not nicked and grounding your signal anywhere along the wire.


You will probably need to remove the large plug from the back of the instrument cluster to check continuity so I suggest you also remove and re-seat the small connector on the other end of the brown wire which should be in position 9 of the big plug (see photo). Be sure the small connector is correctly oriented in the big plug and fully seated so it makes good contact with the circuit panel when you plug it back in. Also, check the two fold-in tabs on your circuit panel that connect to the plug to be sure they are clean and correctly aligned. You will obviously need to re-install that big plug to do another test and that act alone might complete the signal circuit.


If not, the circuit path in your circuit panel leading away from the number 9 position may be damaged or broken. I would carefully inspect the relatively short circuit path from the #9 plug position (third up from the bottom left when looking at the circuit panel plug area) to the left hand connection post (see photos). Be sure the small nuts on both posts are snugged down.


Hopefully, one of the above steps will restore the signal circuit and your new tach will work. If not, I would contact sonnie24 to see what he suggests and if there is some simple test you can do to verify the new tach is working properly. Good luck!







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If you have no power to the tach but the other gauges work, it almost has to be the nut on the right hand connection post is not tight enough to make a good contact. Power for the tach, water temp, brake warning light and oil pressure light all comes off of the same circuit in your panel connected to port #7 on the big plug. Since your tach power connector is upstream of the others, it must be the panel is not making good contact on the right hand tach post. I would either snug down those two nuts or add a washer under them like Rock suggested to be sure the panel is making good contact.

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  • 4 weeks later...
  • 5 months later...

The wire leading from the negative side of the filter to the tachometer has broken off. This is an original part... can anybody tell me where we can get this filter with the wire attached to it. Will a filter from another year work? I am not used to posting and am trying to find my way around the site. Thanks in advance for any help.

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