Reading the Electrical Schematic

Hi All, I was wondering if someone might know what these numbers (16, 20, 8, 298, 181, 687, 54 .. etc ) are prior to the wire color designation on this electrical schematic I have. It seems to be a rather official type schematic.





I can pretty much follow it with the wires / connectors / peripherals, I'm just wondering if those numbers have significance. I seem to be missing the cover of this group of schematic drawings, if it ever had one, but I have the index.

I'm trying to sort out why I have power to that one coil wire on the engine side of the firewall when starting the car, but not when the key is in the "Run" position. I thought I identified the one place on top of the switch that has power in both the Run and the Start positions, but where the two wires connect at the firewall to the one coil wire on the other side only gets power in the Start position. I'm trying to really understand the purpose of all the wires and want to make sure that all the gauges work and neutral switches and everything. It's all there, just something isn't working.

Thanks.

ok yes, I understand the difference in the wires resistance.

See I thought I had been through all of this before and got it sorted out. There is an MSD distributor and coil and I could get the car running but it would always putter out slowly and I couldn't get it running _good_. It would run but it sounded like it was missing. When I put 12 volts from the battery to the coil everything worked fine. So I started digging and using the ohm test I figured out that the wire was resisting the voltage and causing the MSD to not get the 12 V it needs, thus causing the coil to charge slower.   So I bought and installed a step-up voltage directly before the coil and thought all it was done. That was about a year ago. Now I finally ( thanks covid ) am back working on it, and it's not working in the run position. So now I'm back tracking down every wire and re-learning everything I thought I knew, but clearly don't.

Using the schematic I thought I could figure out why I'm not getting the power through the resistance wire, but at the moment I'm not exactly sure which wire it is. I'm trying to identify which post(s) out of the ignition switch carry current when in the start and the run position, and I thought that they both started from the same post at that switch, and then ended up at the same post at junction block behind the fuse box, however, the one of the wires was part of some additional switches / circuits ( the neutral switch maybe ? tach ? I'm just not sure how all that is put together ). It's all there in the schematic, I believe, but I'm having some trouble understanding it, and what is ok that is missing or what should be added given the fact that the ignition control module ( ignition box ? ) is removed from the system. I'm guessing that it is internal to the MSD distributor now ?   Not sure. Much to sort out and learn.   Any and all advice is appreciated.

squarethumps wrote: Hi All, I was wondering if someone might know what these numbers (16, 20, 8, 298, 181, 687, 54 .. etc ) are prior to the wire color designation on this electrical schematic I have. It seems to be a rather official type schematic. I can pretty much follow it with the wires / connectors / peripherals, I'm just wondering if those numbers have significance. I seem to be missing the cover of this group of schematic drawings, if it ever had one, but I have the index. I'm trying to sort out why I have power to that one coil wire on the engine side of the firewall when starting the car, but not when the key is in the "Run" position. I thought I identified the one place on top of the switch that has power in both the Run and the Start positions, but where the two wires connect at the firewall to the one coil wire on the other side only gets power in the Start position. I'm trying to really understand the purpose of all the wires and want to make sure that all the gauges work and neutral switches and everything. It's all there, just something isn't working. Thanks.

The "QUOTE" feature should be in the header bar of the comment you want to quote....

Hi All,

A success update here and the introduction of the next issue.

If you examine the picture I posted where you see the IGNITION SWITCH and SWITCH POSITION diagram, you can see a splice S-801 on the 16 - R - LG circuit.   It is this splice that was disconnected. The description of the splice in the document says that it is over by the heater box, and, indeed it is. The resistor wire was simply disconnected from the other two wires. I don't really understand why the splice is way over there kind of on the other side of the car, but that's where the wires all terminate, and that's where they (should have been) all joined together.   

A wire nut solved this issue, and now the proper resistor wire is carrying the voltage to the firewall block, and then on to the MSD voltage hop-up I have so that the MSD coil and distributor is receiving the correct amount of voltage and it is working.

The next concerning thing is to figure out why it is working because the tachometer is NOT hooked up! If you look at the diagram in this thread :
http://forum.grantorinosport.org/info-72-79-gauge-clusters-and-wiring_topic2933.html

The tachometer should be hooked to that coil wire on the engine side of the firewall. If the tach isn't hooked up, the circuit should not be complete and no power should be getting to the coil.   I need to figure out what happened to those original splices where the tach should be connected. My intention is to find where that should be on the engine side of the firewall and then make sure the tach is working. This splice would be BEFORE my MSD votage hop-up, of course.   I may be posting a whole other thread on this topic, because, again if you look at the above thread, the picture of the 74-76 wiring at the back of the tach, which is also part of the little bundle that includes the ammeter and the clock, I can't find where those wires all connect to. It seems as though the entire 6 pin connector is missing. The back of my instrument cluster has all the barrel pins for the tach, clock, and ammeter, but the actual grey connector just isn't there, and I can't seem to locate it under the dash.   Quite odd. That actual connector I am referring to is NOT pictured in that wiring picture I mention. In that picture, all 6 wires just disappear off to the left.   It would be nice to see that connector, though with the schematic I have I pretty much know what it looks like. It is labeled as connector C-209.

do you have a sport cluster harness? there's a smaller harness that connects that and runs out through the firewall on the drivers side of the brake booster and connects to the engine side harness but you can tap into the coil feed just outside the firewall like shown in the diagram cut and run each end of the cut but to the tach

Okay, I think I see what you are trying to figure out now.  From the pics you posted, you are missing the connector.  This connector should be behind the cluster, and you have to disconnect it when it is removed.  I agree, it looks like someone took all the pins out of yours removing the actual connector.  Here is a pic of the harness and connector:

I am not overly familiar with the later cars wiring. There is a pic of that thread that shows your connector though. Look at the 74-76 cluster in this pic:

Edited by 72FordGTS - 11-May-2020 at 2:51PM

72FordGTS wrote: That other harness you posted looks to be the right one IIRC. It comes through the firewall near the brake booster. See it in this pic below of my car but it is a 72.

Just so I am 100% clear, you are referring to the connector / firewall plug that, in the picture is leftmost in the picture, but when describing it on the car, one would say that it is more towards the passenger side of the vehicle. It is "closer" to where the brake booster mounts than the other firewall plug that we see in the picture of your '72, which is closer to the drivers side fender. Is that correct ?   

On my car, there doesn't even seem to be a hole in the firewall for a plug / harness to go there, so I'm really lost now. LOL

californiajohnny wrote: was your car originally a sport cluster harness car, or are you converting to sport?

I am not sure what it originally was as far as the cluster goes. I know it's a 1976 #0022 S&H car. I have a Marti, but it doesn't say anything about the gauges. I acquired the car and the dash was already put together and it looked rather original, with the exception of a new dash "top". I have pictures of the body work that was done to the car, which includes floor pans and a repair of one of the door hinge posts, but nothing pictured that shows any kind of repair / replacement of the firewall.    It's been about 4 years since I took apart the dash to figure out what was going on with the lack of power to the coil. I got sidetracked with other matters. I don't remember removing all of those pins from the connector when I removed the instrument cluster, and I'm inclined to believe that if I was taking out the gauge cluster and going to disconnect a harness, I wouldn't have had reason to remove all of those pins from their connector. I also don't really recall the tachometer working when I did get the car running originally but I think it was because we wired hot directly to the coil just to get the engine running.

All that to say .. I'm not sure I guess, but the placement of the wires in their hold downs( clips and wire ties and such ) and the "crispyness" of the tape that was on the harness when it removed it for examination and repair, makes me to think that it was all original.

That plug comes through on the driver's/left side of the booster.  This is a '72, so they may have changed things by '76.  It says in the description on your diagram "Engine compartment/LH side of dash".  So it doesn't really narrow it down under the hood.

ok, mine was a std cluster... i converted it! not sure if the std cars even had the hole for the short extra harness i'll look for a good pic...
far as i know PS122 cars didn't come with sport clusters???( but i could be wrong? yes that red/lack interior is from the 74 sport there were 3 color options...black/red, tan/orange, and blue/lt blue
 idk if it specifically states on a marti about the cluster??? maybe someone else can chime in on that...
 a couple sport cluster cars i parted had that hole for the short harness on the drivers side of the booster between it and the main harness bulk head

 here's a pic of my firewall... no it does not have that hole! mine was a standard cluster car originally. i didn't buy the short harness... i wired it up myself instead
 

Since the gauge package/sport cluster was an option, it would be listed on the Marti report if your car had it.  IIRC, some of the later GTS cars, 74-75 had the gauges as a standard feature, but the '72-73 didn't and off the top of my head, I don't think any 1976 Torino came with them standard either as teh GTS was gone in 1976.

Edited by 72FordGTS - 14-May-2020 at 6:10AM

72FordGTS wrote: Since the gauge package/sport cluster was an option, it would be listed on the Marti report if your car had it.  IIRC, some of the later GTS cars, 74-75 had the gauges as a standard feature, but the '72-73 didn't and off the top of my head, I don't think any 1976 Torino came with them standard either as teh GTS was gone in 1976. So based on what John posted I think your car probably didn't have a gauge package from the factory and someone tried to retrofit it.  That's probably why both your car and John's don't have the hole in the firewall like mine.  At this point, you might be better off to just wire it up on your own, without the harness, unless you are trying to make it factory correct. Any one on here have a '74 to '76 Torino with the gauge package option from the factory?  Maybe they can post a pic of the firewall too so we can confirm this info.

Well, with all of those pins there on the back of my sport cluster, yes I would like to just be able to plug those into an original type connector and then have the wiring correct with the factory diagrams. A further concern I have is that if the wiring under the dash is original, but the instrument cluster is not, is there going to be issues with the main cluster connector ?   Like, how different is the original wiring harness in the non-sport, vs the sport models, that might cause issues with the pins which basically connect to the cluster's printed green ribbon ? Or should that be fine and that is why these optional gauges ( tachometer, clock and ammeter ) are basically in a separate harness ?

With respect to the non-sport cluster. I suppose then that the non-sport cluster did NOT have a tachometer at all ?

I found this : but the colors of the wires for the tach are not perfectly matching with my diagrams so I would just remove the pins from that connector and put in my own.   According to the picture I posted above with the C-209 connector, that is part of harness 10817 on the "other side" and the harness you see in the picture below is 10B942.




10B942 for sale

<SOO MUCH TO LEARN LOL>

Edited by squarethumps - 14-May-2020 at 6:49AM

californiajohnny wrote: the main connector will fit i had to swap positions of 3??? wires in the connector unfortunately it was several years ago and i don't recall which ones??? i think it was the gas oil and water sending wires??? i took my std cluster and the sport and traced down each circuit on the board to the connector end and made notes then seen most were in the same location except those few, removed them from the connector and plugged them back into the new positions  my brain works like a schematic but trying to explain that to someone can be impossible for me sometimes  keep in mind the gauges that share a common connection to 1 pin will be the positive power side of the gauge the other side will have it's own separate pin will be the negative to that individual sender  now on the turn lights and high beam those that share a pin will be the ground, each individual pin to that bulb will be the positive to it  the dash bulbs will have a common ground pin location and common pin location for the power to them which is the light blue with a red stripe wire it should be in the same location on the main connector i believe so this may help to track down a few by process of elimination

@californiajohnny   this is most distressing lol.    I guess the light at the end of the tunnel is that I have the schematic I have and it seems like all the colors of the wires that it calls for are correct. So at least the wiring that is there is a "known".   Then I can start to label out the pins on the sport cluster I have and compare that with the original wires and the connector that is there and see what needs to change. That is very good information you gave me about the shared positive and negative. I tried using a voltmeter and the continuity indicator ( the tone ) a couple years ago to try and see what was what, but with circuits like that, there's always some connectivity. It was trying to hear the difference between a loud buzz and a quiet buzz, and then try and interpret that meaning. Rather painful. That was before I got the schematic though. I need to get all the pages in that schematic copied and laminated or even scanned into a coherent digital format.