Tachometer install
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Joined: Oct 2012
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From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Tachometer install
Have searched the board for about an hour now and can't find exactly what I need. Which wire do I tap into for the signal (green) wire? I know it's supposed to be the coil but mine looks different than the others I've seen. I have two plugs on it that slide into each other side-by-side, and into the coil. They both have a reddish/pinkish wire and a white wire, both wires on one plug are slightly thicker than the other. One of the white wires, the skinnier one, goes into a connector that looks like the EST one almost, then continues on into the main looming. Would that be the one I tap into?
Edit: Or can I just go off of the ECM harness? That would make it much easier running/hiding the wire than going under the hood. Which pin is it located in?
Edit: Or can I just go off of the ECM harness? That would make it much easier running/hiding the wire than going under the hood. Which pin is it located in?
Last edited by RavageTheRoad; Oct 1, 2013 at 10:00 PM.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Thread Starter
Member
Joined: Oct 2012
Posts: 186
Likes: 0
From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Re: Tachometer install
Thanks I actually did figure it out, it was in fact the one with the connector on it. I think I'm still gonna move it now based on the pinout you posted, I just hate adding wires under the hood and making that mess even messier. Any ideas on why I would have a rough idle after setting minimum air still? That was why I got the tach, my factory one is pegged and I put a new ECM in and couldn't get the setting right by ear. It idles right at 650 now but when I run accessories (especially my fan, it's on a toggle and hard wired without a relay) it gets pretty rough to the point of making some of the heat shield rattle and you can feel the whole car shake a bit. The second I turn it off it smooths right out. CHecked the voltage right on the alternator, in gear with wheeles chocked, and it keeps a consistent 14.10v charge. Maybe I need to get a relay in there because it's robbing current from the ignition system?
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Tachometer install
Or ask on here for the cluster connector pinout to idenify the white wire there
If you are running it from the fuse box then you may well be causing electrical problems elsewhere
Start a new question in engine dept
Thread Starter
Member
Joined: Oct 2012
Posts: 186
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From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Re: Tachometer install
I have the power coming straight from the battery. The reason I was questioning it was because I have burned up 2 30A switches in the past year without popping the 25A inline fuse i put in the circuit and have seen it suggested here before to have it wired with a relay to reduce current draw. Thanks for all your help with this.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Tachometer install
You are running the wire inside to the switch ( I assume ) then back out to the fan.
Even with the relay the factory went straight from the batt to the fan
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Thread Starter
Member
Joined: Oct 2012
Posts: 186
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From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Re: Tachometer install
Ah ok. So the relay is to take some of the stress away from the switch so it won't burn up over time. Maybe I will wire it to the factory relay and see if this one I just got lasts.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Tachometer install
I have no idea why people want to replace factory proven systems with shade tree versions of their own.
If you have the factory fan relay in place , why would you run the fan power through a switch inside the car
If you wanted manual fan control, you just use a switch to control the stock fan relay
You can even leave the stock fan control system in place ;
so you can have auto fan and manual fan operation by choice depending where the switch position is
If you have the factory fan relay in place , why would you run the fan power through a switch inside the car

If you wanted manual fan control, you just use a switch to control the stock fan relay
You can even leave the stock fan control system in place ;
so you can have auto fan and manual fan operation by choice depending where the switch position is
Thread Starter
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Joined: Oct 2012
Posts: 186
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From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Re: Tachometer install
I actually would have rather done that, but when I did my engine swap the hole for the sensor that kicks the fan on had a plug in it for some reason and I couldn't back it out so I had no other choice. When I get my hands on a 350 in the future I will certainly be doing it the correct way. The PO did a lot of bandaid work before I got it and I ended up having to replace the engine on a very limited budget. I couldn't stand to see it junked so what I have now was just done to save it from the boneyard until I have a bit more disposable income.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Tachometer install

The lack of a fan switch does not prevent you operating the stock fan relay and wiring using a manual switch inside.No need to rewire the car as you did.
The manual switch just replaces the fan switch in the head and does the same function ; turn the fan on
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Member
Joined: Oct 2012
Posts: 186
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From: Levittown/DelcoPA
Car: 1991 RS
Engine: L69?
Transmission: 700r4
Re: Tachometer install
Well I'm still learning, which is why I posted a few posts up about doing that very thing. I didn't break the bank saving the car just to hack it up, which is why I'm asking questions on here about the right way to do things.
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