Tach hook up problem, take a look

[87gn-newbee]

I know asked a million times but I bought a Harlan programable shift light got it hooked up set up for a 6 cylinder and set the RPM I want but when I connect to the green conector behind the alt the stock tach sits at first LED doesn't move and shift light doesn't go off. What could cause this? I re-did all the wiring only 3, pos,neg and green to tach signal. Where is another tach signal where I might be able to check? Appreciate some help Thanks
Dan

 

[1970gsx]

There is a white wire in the wiring harness that goes to the module/coilpack. This is also a tack signal. I have my remote start tack sensing wire hooked to this wire.

 

[87gn-newbee]

I hooked it up to the green connector and it doesn't work. The stock gauge also doesn't work when i connect shift light to the green conector.
Which wire by the coil pack is the tach signal? Anyone else have any ideas? Could a bad ground cause this I checked but going to go over evertyhting again
Dan

 

[FJM568]

Maybe John Spina will stop in here and explain...I think he told me at one point that sometimes hooking up a tach to that wire will decrease the signal to the stock tach(if your car has one) and causes it not to work or something like that...Unplug the one under the hood and stock tach works again...

Also, I think there may be an additional tach plug under the dash somewhere...I don't know it that is right, but I thought I read something about that somewhere...

Or maybe I'm just hearing stuff in my head again... Sometimes I really don't know for sure!!!

 

[charlloots]

i remember reading somewhere maybe vdo tach instructions that if you dont disconnect the factory connection behind the dash you will not get the readings on your shift light and you have to tap in to one of those wires that pluged into the factory tach and this is the reason i dont have a shiftlight but my tach works fine connrected to the wire benind the alternator. i will look for the paper work hope this helps.

 

[87gn-newbee]

It was a bad ground, it works fine now but would still like to hear some more about using that green conector. I don't care about the stock tach as long as the SM and light are on but I don't think they are. Going to have to check with different scan tool.
Dan

 

[NASSTY]

The green connector behind the alternator is the tach lead for a digital dash car.There is a wire in the dash you can tap into.Not sure if you have to take instrument cluster out to get to it.There is a 8wire connector that plugs into the back of the instrument cluster.(Not the main harness that has 18 wires.)Tap into the white wire in the 8wire connector.Plug is located on the back of cluster behind the tach.

 

[charlloots]

Originally posted by 2NASSTYBUICKS
The green connector behind the alternator is the tach lead for a digital dash car.There is a wire in the dash you can tap into.Not sure if you have to take instrument cluster out to get to it.There is a 8wire connector that plugs into the back of the instrument cluster.(Not the main harness that has 18 wires.)Tap into the white wire in the 8wire connector.Plug is located on the back of cluster behind the tach.

my car is not digital dash and the tach works fine hooked to the green connector behind the alternator

 

[TurboDave]

Originally posted by 2NASSTYBUICKS
The green connector behind the alternator is the tach lead for a digital dash car.There is a wire in the dash you can tap into.Not sure if you have to take instrument cluster out to get to it.There is a 8wire connector that plugs into the back of the instrument cluster.(Not the main harness that has 18 wires.)Tap into the white wire in the 8wire connector.Plug is located on the back of cluster behind the tach.

That's not the connector for digital dash cars. It's the tach test lead on ALL Turbo Regals. It's the place to hook your tach to.

As for the problem in the thread, there's likely something in the shift light or tach that needs to be changed, and is causing the problem. It may not be set up to monitor the right "type" of signal. It know it's different, just don't know what the difference is.

 

[NASSTY]

Originally posted by TurboDave
That's not the connector for digital dash cars. It's the tach test lead on ALL Turbo Regals. It's the place to hook your tach to.

I know the main reason the green connector is there isnt just for a dig. dash tach install cause analog dash TRs have that same green plug there also.What I was saying is the green connector is where you get the tach signal for a dig.dash.Because the dig.dash doesnt have the white wire under the dash for the tach signal.

 

[87gn-newbee]

I think Dave is right it worked for a while and now it's not wotking again. Going to a friends house to try on his car. I don't know what I did to make it work but it is hooked up as per direction and set up for the car. There are a few people running this light and don't have any problems.
Dan

 

[U1ARUNIT]

Yes, Dan got the idea from me for the shift light. I have my tach signal hooked to the green connector under hood.

I have a Performance Instruments GNX cluster now but the light worked fine WITH the stock tach hooked up and working as well.

As was stated, with the GNX cluster you tap into the white wire in the smaller dash connector at the RH side of the support housing behind the cluster. This would probably be pretty hard to get to though with the cluster installed if you wanted to use that wire for signal.

Keep us posted Dan on how it works on your buddy's car.

 

[TurboDave]

Originally posted by 2NASSTYBUICKS
I know the main reason the green connector is there isnt just for a dig. dash tach install cause analog dash TRs have that same green plug there also.What I was saying is the green connector is where you get the tach signal for a dig.dash.Because the dig.dash doesnt have the white wire under the dash for the tach signal.

Nope. The digital dash gets it's tach signal just like all the others. Trust me, I have one.

 

[salvageV6]

Unless it's on one of the terminals labeled "Not Used" I didn't see a listing for it in the digital dash section of the manual.

Of course it isn't used either so....