Tach Wiring
Thread Starter
|
Elder User
Joined: May 2003
Posts: 589
Likes: 0
From: Canastota
Tach Wiring
I hooked up an old tach Ive had for a while. I hooked the tach signal wire to the coil harness, the one directly under it with 2 wires sticking out of it. I hooked it up the to the tan wire(not sure of exact color, lookes tan). With everything all hooked up, now the truck wont start. It will turn over but not start. I disconnected the wire I hooked up to the coil connector and it started. Whats the deal!?!?! Is there anywhere else I could hook it up, like the way an OEM one would be?? Also, why would the truck not start with the tach signal wire hooked up??
Moderator
Joined: Jan 2001
Posts: 56,995
Likes: 2,741
From: Virginia
Are you sure you know the wiring for the tach? Post the brand of tach you have, and the year vehicle you are putting it on.
This sounds like you are working on a fairly old vehicle? The tach wire should go to the negative of the coil. But if it killed the ignition on the positive, it will probably kill it on the negative too.
Do you have a battery charger? If so, you could hook the tach up like you think it should be(negative to negative, positive to positive on the battery charger) and then take the tach signal wire, and touch it on and off to the positive. You should see the needle flicker a little bit everytime you touch the wire. If the charger circuit breaker trips, then it's for sure you have the wires wrong.
I hooked the tach signal wire to the coil harness, the one directly under it with 2 wires sticking out of it.
Do you have a battery charger? If so, you could hook the tach up like you think it should be(negative to negative, positive to positive on the battery charger) and then take the tach signal wire, and touch it on and off to the positive. You should see the needle flicker a little bit everytime you touch the wire. If the charger circuit breaker trips, then it's for sure you have the wires wrong.
Thread Starter
|
Elder User
Joined: May 2003
Posts: 589
Likes: 0
From: Canastota
Its a verrry old Sun Pro tach, my grandfather gave it to me and its on the truck in my sig, 92 F150 it has a TFI ignition. I hooken it up the way it said to, black to grnd, long white wire to the coil plug thing, and short white wire to a fuse thats on when the truck is. After looking at the wiring diagram for my truck, the ignition suppression resistor is where the tach hooked up for the OEM application, should I try to tap into that lead?? Where is that ignition suppression resistor and what does it look like??
Tuned
Joined: May 2003
Posts: 345
Likes: 4
From: Southern IL
Green from tach to (tach, negative) side of coil. Red will be power, black ground. Brown will probably be switched power for the light, that is to say it would go to say the parking light wire, so it's hot when the lights are on.
Thread Starter
|
Elder User
Joined: May 2003
Posts: 589
Likes: 0
From: Canastota
Heres sumptin weird. Theres voltage going through the tach signal wire, when its not hooked up to the coil. I dont think it should be doing this, maybe im wrong. All i know is every time I hook it up, the truck wont start. I have to unplug the coil harness and plug it in again and it works. I will try the charger thing tomorrow, I just replaced the starter(theres a clip towards the top that broke loose and it prevented the gear from meshing with the flywheel) so Im a little tired. thanks for the help
Tuned
Joined: May 2003
Posts: 345
Likes: 4
From: Southern IL
There shouldn't be any juice on the green wire unless you are cranking her or she's a running. Contacts inside the distributor break when they pass the pickup coil inside which sends the signal to the control module and from there to the coil (-) or green side.
Thread
Thread Starter
Forum
Replies
Last Post
2001LSV65SPD
1987 - 1996 F150 & Larger F-Series Trucks
16
Aug 15, 2015 09:33 PM
denco65
1968-Present E-Series Van/Cutaway/Chassis
2
Jul 11, 2011 06:53 PM
faroffthetrack
1987 - 1996 F150 & Larger F-Series Trucks
1
May 20, 2004 04:13 PM
Boss50
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
6
Jun 25, 2003 08:35 AM
