When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am trying to hook up my tach to the dash. The PO had problems with the dash and instead of sending it off to get fixed he put in some aftermarket gauges for tach, water and oil temp etc. I've got to chase down the wiring for those things but I have a question about some brown connectors beside the distributor. There is one that I plugged into the cap and two more. Number 1 in this picture is just pig-tailed off the connector I plugged into the cap. I think (?) that that one is used for some type of diagnostic hookup. Number 2 is loose and connected to that cylindrical thing that I am not sure of what it is.
Can anyone help me figure out these connectors or tell me if I have things hooked up wrong?
That cylindrical thing is likely the tach filter; most likely the case needs be connected to ground.
Not knowing what year Vette you're dealing with but think the output of that filter is what feeds the tach signal to the dash.
It's an '84. So, you're #1 should plug into the distributor (there should be the one brown plug that plugs into the distributor, coming out of that should be your short pigtail plug not hooked up to anything and the other wire from the distributor plug going to the tach filter on one end) On the other Brown connector in the middle (lower one) is your #2, it's plugged into the tach filter on the back of the intake. The white wire from the distributor is connected to the other end of the tach filter!
end of your tach filter you plug in your #2 connector. The green and yellow wires should not be part of this connection, unless they're coming from a "replacement" tach filter, but even they were, they should not both be connected at the same point (#2) Upon further inspection of your picture, maybe that's not a yellow wire, but actually the white one coming out of the tach filter, get rid of that green wire, my guess is that they added that for the aftermarket tach signal. Here's some pictures, hope they help, good luck 👍
Last edited by '78CorvetteS.A.; Feb 1, 2021 at 07:02 AM.
Sorry about not stating the year of the car. It is indeed an 84. The two brown connectors do not plug into anything else, or each other. So, I'm not able to switch anything around. I'm wondering if this is because I have an Accel lid on top of the rotor and cap and that is different than the OEM??? I'm trying to digest your answers.
It looks like the problem I have is that I don't have the connection I have circled here. Not sure where that is. Pretty sure that is supposed to be coming straight from the dash.
Look for it at the very back of the block (middle) where it bolts to the bell housing of the transmission. I'll try to send some pictures when I get home👍
You should be able to locate that wire in the main harness that comes from the bulkhead on the driver's side of the firewall. Good luck👍It'll be awhile on the '78, the word scattered only begins to describe it! This harness.
In this thread there's a couple good to very good images of a correct 'coil in cap' for an '84. An '84 HRR explained a long time ago has a 'WHITE Dangler' used for factory only diagnostics. Might be easier to explain using this thread to the OP what to expect. I ain't got an '84 but I do understand it. OP could certainly have supplied better images when asking for help.
Maybe this is a better picture. I removed the wiper motor to see things better. Discovered an oil leak around the sending unit. Another thing to do. At any rate I loosened up the wires in that loom and think that the wire that connects to the tach filter is the white/ yellowish one popping out on the top. Afraid to cut without some feedback and I can't see where it comes out down the line. Thoughts? Otherwise I am going to run a direct line from the dash to the tach filter. I took the dash off as I want to get some other things that the PO disconnected. Oil pressure, oil temp, water temp.
Last edited by wedoo2; Feb 1, 2021 at 07:41 PM.
Reason: Add Picture
I found that the green wire in the previous picture goes inside the car. I believe that it was the connection that the PO used to connect to the aftermarket tach that was installed. I can use that (or replace it with a white wire as it shows in the wiring diagram) but I don't know what connect it to. I am reposting the picture of the diagram and circled where everything seems to converge but I have no idea what that represents.
I have removed the dash and thought that it may have some markings to help me out but nothing. There is one white wire coming out from all those wires that connect to the dash and it goes into the center information box not to reappear. And according to the diagram I'm looking for a white wire. Circuit 121.
I apologize but I just don't understand the diagrams well enough so maybe someone can let me know what that box is.
I finally traced the correct wire for the tach and I have it working. YEA! Now I have to trace the water temp line. Thanks for the help here. I have learned a lot.
Tach Connections
