Tach not working Newbie

Hi Bob. first let me thank you for your patience. Obviously wiring is not my Forte. Found switched 12v triple checked wired in resistor triple checked still no dice on either tach. Note: POT tach has bounce without resistor but not with resistor. No bounce either way with spare tach. How do I confirm tach signal being sent? and worth trying 1k resistor(have to order) if so, 1/4 or 1/2 watt or any thoughts on 480 ohm deal??? Lastly, your thoughts, if any, with that POT wired in and knowing tach "did" work that way would signal have had to be turned on?  
Thanks again enjoy holiday wk end

Ron D.

Rond948 wrote:Hi Bob. first let me thank you for your patience. Obviously wiring is not my Forte. Found switched 12v triple checked wired in resistor triple checked still no dice on either tach. Note: POT tach has bounce without resistor but not with resistor. No bounce either way with spare tach. How do I confirm tach signal being sent? and worth trying 1k resistor(have to order) if so, 1/4 or 1/2 watt or any thoughts on 480 ohm deal??? Lastly, your thoughts, if any, with that POT wired in and knowing tach "did" work that way would signal have had to be turned on?  
Thanks again enjoy holiday wk end

Ron D.

I'm happy to help. And I understand how hard this can be. It is equally hard for me, not being there to see with my own eyes what is happening. Not knowing how the pot is wired in, nor why it was used, makes it very hard to answer why. It is possible, the original builder was getting a signal from some other part of the ecu. Maybe he was using a coil or injector to reference a tach signal. Have you verified that the correct wire from the ecu is being used? It should be pin 10 (white wire) in the red ecu connector. I would verify that before going any further.

LS1 ecu pinout

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Am I doing this right? Location - cluster B connector Connecting 12v switched to tach wire(grn/blk) with 10k ohm resistor in between correct? I have single wire cut in half one end spliced into 12v other end to one side of resistor (have to be solder???) other half piece of wire to otherside of resistor(again does connection have to be solder???) with other end spliced into tach wire. Correct??? Did not use solder so far only wire and resistor twisted together connections.

I think you have it.
Test if it works and then once proven I'd highly recommend to solder both connections where resistor connects to wires

Thanks, so still no go. Tried 480 1k 10k and 22k for hell of it. Only change on spare cluster/tach with 10k only, now get tiny bounce key on and after start in couple seconds needle swing to 4k ish rev once then not reading.

Rond948 wrote:Am I doing this right? Location - cluster B connector Connecting 12v switched to tach wire(grn/blk) with 10k ohm resistor in between correct? I have single wire cut in half one end spliced into 12v other end to one side of resistor (have to be solder???) other half piece of wire to otherside of resistor(again does connection have to be solder???) with other end spliced into tach wire. Correct??? Did not use solder so far only wire and resistor twisted together connections.

Post a pic of how you hooked it up

the pic as Bob requested could help enlighten the situation to try to help you for sure.

i'm super puzzled and questioning that extra pot you have in play there and whether the headache could be with that and whether it should be removed?

3 pics: [You must be registered and logged in to see this image.]one is red wire with resistor, one is gr/blk and red connected with wire nut, one is all blk(12v key) and red connected with wire nut

Sorry  for terrible pics I'll try again tomorrow

Need to resize the pics to smaller.

Red wire w/resistor same in both pics. Gr/blk and all blk from "B" connector

Sorry. I have no idea what i'm looking at in those pics.

It should look like this.

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The green wire in this pic, would be your green/black. And the red wire is the key on 12v.

Here is what I did. I cut gr/blk and blk(blk is 12v key) both from "B" cluster connector. Cleaned back each wire end, then took one piece of loose wire (not part of B connector wires) Red in color, cut that in half joined back together with resistor in between two halfs, then attached one end of that red wire with both cut ends of gr/blk with wirenut (photo) and attached opposite end of same red wire with both ends of blk wire with wirenut(photo). Essentially the same as your pic.? or does that mess with current/voltage? Those wires are tiny awkward location to each other thus the way done.

Note: currently using tach from spare cluster w/o potentiometer. Once yesterday several minutes after starting tach did 1 full swing then nothing 10 min. drive. If current resistor connection is not the problem I plan to check wiring pass footwell.

Did you verify the green/black wire is connected to the white wire on the ecu?

Wh to wh gr to red 4 pin plug issue sending pics

Bob I feel bad. I checked the pass footwell and found I have a Dakota digital unit that had the red power wire apparently come loose sometime before I purchased. It was ziptied up and behind the glove comp. Reconnected power and removed resistor and non pot tach works! I did also try the pot tach and it does work somewhat but not correctly and responds to pot adjustment on idle only. Strange why that was installed? Thank you

Rond948 wrote:Bob I feel bad. I checked the pass footwell and found I have a Dakota digital unit that had the red power wire apparently come loose sometime before I purchased. It was ziptied up and behind the glove comp. Reconnected power and removed resistor and non pot tach works! I did also try the pot tach and it does work somewhat but not correctly and responds to pot adjustment on idle only. Strange why that was installed? Thank you

Glad you found the issue. Still a strange setup though.