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phil, Chevy Mechanic
Category: Chevy
Satisfied Customers: 269
Experience:  20 years experience
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1990 s10 blazer: cluster..I got all the gauges to work except the tach

Customer Question

i have a 1990 s10 blazer, i have aquired a anolog cluster with a tack in it. I had to make it work but it looks great. I got all the gauges to work except the tach! there does not appear to be the right electrical connectors in my modified cluster so i solderd wires to the rear of the tach. i just cant seen to figure out where to hook the wires to. im afraid to burn somthing out after all this trouble. can u help me? please?
Submitted: 5 years ago.
Category: Chevy
Expert:  phil replied 5 years ago.

Hi nikkilynn,

 

Can you tell me what wires you have coming off your modified tach?

Customer: replied 5 years ago.
i solderd 2 wires on the back of the factory chevy tach. i dont remember what they were labled on the board. it is a factory gmc sonoma tach
Expert:  phil replied 5 years ago.
What year truck did the tach come out of?
Customer: replied 5 years ago.
i think it was maybe a 91 or 2 it had a vortech 4.3
Expert:  phil replied 5 years ago.

You will need 3 connections to hook up a tach. A power wire that gets 12 volts when the key is on, a ground and a wire to the coils positive terminal.

 

However without knowing what the wires on the back of your tach are I cant tell you exactly what to hook up where. Especially since I thik you are missing a wire

Customer: replied 5 years ago.
do you know if the tach is labeld on the back? if so what goes where?
Expert:  phil replied 5 years ago.

In the original wiring harness you would have had red for power, black for ground and green for the coil.

 

If you can send me a picture of the back of the tach I should be able to tell you what goes where

Customer: replied 5 years ago.
which is the wire for coil +? there are 4= 2 plugs- white and pink small ga. other plug=white and pink bigger ga.
Expert:  phil replied 5 years ago.
What guage would you guess the smaller and larger guage wires are?

Are you sure you arent mistaking pink for purple?
Customer: replied 5 years ago.
maybe 12 and then 16
Expert:  phil replied 5 years ago.
Are you sure the pink isnt really purple?
Customer: replied 5 years ago.
it may b fadded? not shure, its a 1990 blazer with pk up coil in dist. and modual. is has two plugs on the ign. coil, one plugs in first and the other locks onto it and plugs in second. some colors i cant identify sometimes. litle bit color blind...
Expert:  phil replied 5 years ago.

Im sorry, I thought you were still talking about the cluster wiring.

 

The larger guage wires are the coil input wires and the smaller guage is the output to the distributor. You should want to deal with the smaller guage white wire to drive the tach

Customer: replied 5 years ago.
o oops, tomorrow i will take the cluster out and take a pic of it, then i think we can solve this. ittl be awsome
Expert:  phil replied 5 years ago.
That sounds like a plan. As I was sitting here thinking about it, if you have the set up that I now think you may have, you will end up running both small wires (the pink and the white) to the tach. Get me the picture and we should be able to get it done.
Customer: replied 5 years ago.
ok are you ready? for the bazer tack? i just pulled the globe out and i did put three wirers in.... i need an adress to send them to. i dont know were i got the ideas for the wire colors but whatever.
Expert:  phil replied 5 years ago.

Hi, Im ready. The site doesnt allow email addresses to go through, it will delete them during the sending of the message. Just copy and paste it into the same window you type to me in

Customer: replied 5 years ago.
so do you make money from this questions... i have some 2 how do i doit... k here are the pics... ok the wire on the twelve o'clock is brown... six is red... and three is black... on the wires on the left of the back of the gaugeBackfrontinside
Expert:  phil replied 5 years ago.

Well the site makes their money as soon as you make a deposit, I make money from their money when you click accept.

 

Before I start getting confused with wire location and color...how did you choose what color wires to put where?

Customer: replied 5 years ago.
i just guessed ... kinda assuming what chev used
Expert:  phil replied 5 years ago.
Are the terminals labeled at all?
Expert:  phil replied 5 years ago.
Assuming that you wired red to positive and black to ground, which from your clock description I think you did. Red goes to 12v with the key on, black goes to ground and your brown (which should be green) goes to the coil + terminal
Customer: replied 5 years ago.
are you shure? this is why im asking you .. i told you i just geussed having no formal kowledge.. how do you know do u have diagram ot the tack or? the board is not labled... like i said i merely gussed. this gauage cluster to do this is VERY rare and doing it wrong wil be very bad.
Expert:  phil replied 5 years ago.

Unfortunately your picture wasnt very clear for me to get a good look. Before you do anything let me work on clearing up the pictures so I can zoom in. You mentioned before that the board was labeled. What was the labeling?

 

Also, take an ohm meter and check the resistance through all the different wire combinations and tell me what the readings are.

Customer: replied 5 years ago.
ok i see that u are right on hookup. i looked closer and the board is labeld. says coil, bat + and gnd, but when i hook up the gnd and batt the tack goes to the top ...

same with hooking them all up... i will ohm the wires and let u know. i may have to repair the tach itself, dam
Expert:  phil replied 5 years ago.

When you hook up the bat+ lead make sure that its only has power when the key is on, not constant power.

 

Also when you hooked up all the wires did you try to run the truck? Or did you do it with just the key on?

Customer: replied 5 years ago.
tried it all ways
Expert:  phil replied 5 years ago.

Thats very odd. Does the needle peg when there your brown wire is not hooked up at all, so it is getting no signal from the coil?

 

I have seen tachs peg but its always been when the signal from the coil was the wrong voltage or when it was hooked up to the wrong coil wire....never had it happen when the coil wasnt hooked up at all.

 

Try hooking up just the positive battery and ground with the key off and on and tell me what happens

 

 

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