Hello,

I have my dash out and fixing some things that have been done to it prior to me and have a few questions

In picture 1 you can see the convertible top switch and it looks like there was a wire removed from the connector and wondering if anyone can tell me what it was. There is a picture of just the connector in picture 3

In the same picture you can see the red wire is tapped into the door switch and that is powering the tic toc tach. I will be removing that but I can not find any of the original clock wires. the tach should have just had wire to the coil and the clock wires for the back light and the power. The way it is wired has power to the junction block on the firewall and back light from the door switch I believe. I would like to figure out what the wires were for the clock to fix this.

In picture 2 there are 2 orange wires that were not hooked up or capped. Is the one with the connector the cigerette lighter? And anyone know what the other orange one right next to it in the same part of the harness is? I do not think it is the clock power.

Last questing is on picture 4. The yellow wire comming out of the same part of the harness as the orange wires and that was connected to the aftermarket radio. Was that originaly the power wire for the factory radio? Car had a radio in it but no sign of the 3 prong plug used for the original radio

Long and short is it appears to be missing (or cant find) the original clock wires and original radio wires as I would like to power the tach off of the clocks and the aftermarket stereo off of the radios....

 

The clock back light is usually grey and wired together into one black plug, the orange wire with connector is cig lighter, the tach wire should be brown and coming out of the main harness with a two amp inline fuse, the red plug in the fuse panel has an extra tab for another power feed to what ever you need it for, and yellow wire is for radio... that other cut orange wire might be power for the top...

 

In picture 1, the upper orange wire powers the top. The bottom is for power windows or locks or seats. Another connector would plug into that bottom bay. If you do not have PW or PL or PS, then that little wire was added by a previous owner for something unknown.

So right now it looks like your tach works only when the parking brake is not set....
The clock wire should be a fat orange one right behind the clock area. If not there, it could be that stray cut one under the speaker hole.
The yellow wire is for radio - the original connectors are often cut off.

 

Thanks Rob and yellow, I will double check for the grey wire but do not recall seeing it or maybe the plug was cut off and just did not notice it yet.

Rob, when you added your tach did your car have the drown feed wire? My harness is not too cut up but seems like there are things missing. The tach worked fine but no wires from the harness were connected to it. they ran power from the junction block andback light light from the brake light switch.

 

My car did not come with the rally pac, just the clock. Therefore I had the non-rally pac wire harness which did not have the brown tach wire & fuse holder. I added one wire (w/ fuse) and ran it through the existing harness loom to the coil. I powered the new tach / clock from the existing clock feed and light from the grey clock light feed. (I made a custom plug-in harness). I will see if I have pics of the factory clock harness at home tonight (if memory works.) I am pretty sure there were two separate plugs for the clock (one orange contant 12V, one grey dash light).
I sure hate when people start hacking up wires without proper knowledge at that they are for, like your PO did...

 

Thank you Rob...I am going to guess since in that photo of the 2 orange wires (one cig lighter) that the other orange is the clock feed and will have to hunt for the grey...I hope to find them and use them as they were intended to power the clock and light and then run a whole new wire to the coil for the tach.

Does the clock and tach share the same terminal? If I recall there are only 3 contacts on mine and thought they had a dround hooked up to one (but not sure) or are the 3 terminals for tach, light, and clock and no ground since they ground at the case with the ground strip on the dash?

I am guessing at this point that the PO chopped off the clock plugs and the radio plugs

By the way I saw earlier you were looking for a rear sway...did you ever get one?

 

Glad to be able to share the knowledge...

Yes, the clock and tach power share the same power feed. Light was another terminal and coil input was a third term. The case is ground and normally it would ground with a metal bracket strip in the dash behind one of the tach mounting screws. It may or may not have a ground tab on the back - just depends how it was made.

If yours never had the rally pac, you will need to add the coil wire. Put an inline fuse holder with 3A fuse between the new wire and the tach.

I finally have a rear swaybay correct for my car. But I might as well redo the whole rear suspension and change axle oil before installing the bar! Parts are coming in now, just need some warmer weather to paint and install!

 

Rob, Do you have an example of the back of the tach to refference the connections as to which side the clock and tach share and which one is for the coil? I have been thinking about buying the tach harness but as stated by others probally no need for it just make one like you did on yours.....Now all I need to do is find some ralley gauges to befriend my tach

 

I will try to remember to look through my pictures tonight. Post a reminder about 6pm if I have not responded. Gotta get my Furd running after work...

You can easily make a tach "harness".
Paying so much for just one wire and a fuse is crazy. I will make'em and sell'em for that much!

Look on the back of your tach - does it have any markings? Is it a factory tach? Can you post a picture of the back of it?
Mine is a repro, which may look different.

Yes, you do need the gauges now!

 

A bit late but I remembered.
Unfortunately I did not have a picture of the back of the repro tach, but here is a picture of the back of the clock.
There are two plugs. The tab is 12V, the plug on the wires is for the backlight.

The harness is also shown. The circled two connectors go to the clock but not sure if they would connect to the factory tach. The repro tach used threaded studs with nuts, so I made my own little harness with ring terminals and mating pieces for the factory connectors.
The thin black wire hanging out of the dash with the pink terminal I think is for the tach input.

IGNORE the other connectors and wiring in that dash picture. It was a custom wire harness to feed the alarm, radio, warning chime, and power antenna.

 

Rob, here is the picture of the back of my tach. There is tape on the back with a y where the yellow wire that went to the coil, R for the wire to the brake light switch ahd a tab with a G.

I did find the grey wire as noted in the picture withe my cig lighter and the other orange that I believe is the clock feed.

Now I just need to know which one goes where

 

You got me now - I am gonna have to look this up in the service manual when i get home. (and maybe peek under the dash, too.) The wiring diag does not have this info.
It looks like you know where two wires go. There is one stud and one tab to choose from now for the 3rd and I cannot tell in the picture if either are connected straight to case without an insulator.

Was this thing fully functional before you pulled it? What did or did not work?

 

The light and tach worked great....Clock on the other hand ...did not. I am sure it needs to be rebuilt but wonder if maybe it works since it was not hooked up to the clock feed

 

Good news for you - here's the wiring connections straight from the 72 GM service manual!

Good news for me - no twisting up into a pretzel to look up under my dash...

Bad news - Your clock might need a repair or rebuild. I know I mentioned some places that will repair them somewhere else on this forum. Have to search and find...
First, hook straight 12V to the power terminal and see if that helps.
If not, if you choose to disassemble it yourself and check the clock mechanism, I included that procedure, also.

Note that yours had the spade lug moved from the power terminal to the dash light terminal.
The wiring you described matches up to this wiring diag.
The parking brake light feed must have given just enough juice to power the tach, as the brake light bulb in the dash was in series with it.

One point of interest is that the regular clock and the tach/clock used the came dash harness. Only the one extra wire and fuseholder was added for the tach to coil feed.

 

Rob, What manual is that? When I moved I am not sure where my 72 manual went. Here is a picture of the one I have(had)...I am still missing things from the move 8 months ago...weird odss and ends that would not have been packed together like the manual and my touch screen remote for my home theatre....maybe the manual was in the wrecked car?? hope not..

As to the repeair of the clock....not sure if I am that brave...

i did just buy a ralley pac to marry the not ticking tic toc tac. it needs the one pic replaced as seen here in the other picture and is included. Hope the repair is easy as I paid half of a set of repops for it

 

The one you have pictured! It is way in the back under accessories.
Hopefully you will find it - it is the best tool in the garage.

 

So what do you think of the pin off of the rally pac?

 

Ya musta snuck in some more into that post when I replied...

It looks fixable. Someone did such a repair just recently like that. This kind of work is part of my day job...

If you are handy with soldering irons, small tools, and PCBs, you should be able to carefully extract a pin from your existing gauge and insert it into that hole and solder it down. You would have to clean up the copper pad well with a small dremel wire brush or a good abrasive pencil eraser first. In fact if there are other pins that look loose. Wire brush the pin, clean with alcohol, and then use a good rosin core solder and a 30 watt max iron.
Change around the wires in the wire harness add the new sending units and you're set!

 

Yea, not a job I am qualified to do by any means, although the guy that had the idea of the 2mm screw into the hollow pin from the back sounded like somthing I can handle. What I will look to do is have a professional do it when it arrives. The question is what type of repair shop to find....

Thanks Rob

 

A TV repair shop or a PCB fabricator would be able to help, but I think TV repair shops are extinct now... Know a local friend who can solder?

 

Well I know I had to have a TV shop repair my DLP tv when it was under warranty. I will talk to some electronic guys I know but I worry since they do not know the component. Maybe I need to send it to Plano

Thanks again for the help Rob

 

You can if you cannot find someone in your area to do it - just pay for the shipping and I'll solder it all up for ya!

 

Thank you for the offer Rob...If there is ever anything I can do for you let me know. I am sure I can get it done local. now if you ever wanted an excuse to see Seattle you could solder it here lol

 

This thread and other one on the topic by Olds70Supreme -
https://classicoldsmobile.com/forums/electrical/60693-68-dash-power-feed-wires-clock-radio-cigar-lighter.html

Both helped me in hooking up my repop tach to right wires...thx.

Above link is a good thread with list of various dash acc wires and where they go (by 72notchback)

 

John, have you tried Tacoma Speedometer? They fixed all of the pins on my gauges and it was fairly inexpensive. Turn around time was only a few days.