Reading the Electrical Schematic

handsofstone wrote: Nevermind. I see the picrures. I had the wiring diagrams for one of my broncos. Pain in the butt to read it.

Yes it took me a while to figure out what I was actually looking at. Now that I've gotten some help from a bunch of people I can at least study it and follow it and figure out what's what.

californiajohnny wrote: i don't think i have any sport harnesses left but i'll look tonight i saw one dash harness still on a dash that had a bad fuse terminal so i didn't sell it... i'll look at it to remember which car it came from?

Thanks !   I appreciate all the effort !

i have that short sport harness!!!

 i have the whole one like in the above pic that goes through the firewall
i can look over the rest of the wiring and see if maybe there's a matching female connector that will work for your missing cluster one???

Oh that is fantastic !!   Yes if you could find that other matching connector that would be amazing !

Yes I think you still have my address from the other PMs. Just send me a PM with the $ and I'll send it over.


Also : @72FordGTS -- that information you posted is so appreciated !   I think that I will be able to read through all of that ( very slowly ! ) and pick it apart piece by piece.   That sounds like about 16 - 24 hours of sleuthing and reading and examining and testing !   Quite a valuable resource. Thank you so much as well !!

72FordGTS wrote: I found some a diagram that might be helpful for you: Also in the gauges thread there is some good info about converting from the standard cluster to the gauge cluster.  The standard cluster does not have a tach, just a speedo, fuel, temp gauge and mostly warning lights. This is probably why your car didn't have the tach hooked up.  I bet is was a standard cluster car and someone added the instrument cluster but did not connect the tach. This info might help you. The last two posts show the pins for the 74-76 standard cluster and the 74-76 instrument cluster.  <p style=": rgb248, 248, 252;">I am going to start my project here in a few days...I am going to begin with gauge clusters and wiring first along with the fuel level sending unit.   I have a few questions before I begin.  I am replacing the original ,crumbling, standard cluster in my '76 with a '74-'76  gauge cluster   <table width="99%" style="color: rgb0, 0, 0; font-size: 12px; : rgb248, 248, 252;"><t><tr><td ="BBquote" style="width: 1649.7px;"> Psquare75 wrote: Part 5: Wiring: For those that are retrofitting a gauge cluster into a standard dash car you need to change the oil pressure switch with an oil pressure sending unit and then install the tachometer and ammeter wiring above. The final item required is to tap off of your cigar lighter power feed (light blue / white stripe) for clock power. </td></tr></t></table><p style=": rgb248, 248, 252;"> <p style=": rgb248, 248, 252;">I understand that it is not as simple as a "plug and play"...so lets make sure that All I will have to do, sans any unforeseen incidents is: <p style=": rgb248, 248, 252;">1) Change the oil pressure switch to an oil pressure sending unit. <p style=": rgb248, 248, 252;">2) Re-wire the tachometer and ammeter as per the illustrated text <p style=": rgb248, 248, 252;">3) Tap off of the lighter power feed for the clock. <div style=": rgb248, 248, 252;">Am I correct so far or did I leave something out? <div style=": rgb248, 248, 252;">  The fuel sending unit is in unknown condition...I know that the wires in the trunk area are damaged/cut.  My first goal is to get the cluster working properly before moving on the fuel sending unit.<p style=": rgb248, 248, 252;">  ANY input and/or help is ALWAYS appreciated and welcomed...and THANKS!!!  =============================================== <span style=": rgb248, 248, 252;">That's pretty much it. The ammeter harness is the hard part, IMO. </span><br style=": rgb248, 248, 252;"><br style=": rgb248, 248, 252;"><span style=": rgb248, 248, 252;">If it were me, starting from scratch (I did), I'd have the ammeter converted to a voltmeter and bypass all that ammeter nonsense.</span> <span style=": rgb248, 248, 252;"> </span> <span style=": rgb248, 248, 252;">================================================</span> <span style=": rgb248, 248, 252;"> </span> <span style=": rgb248, 248, 252;">I got around to replacing the stock dash cluster (the white plastic part was so brittle it was breaking from it's own weight) with the appropriate sport cluster...I have one question....should I also replace the temp. switch with a temp. sending unit since I am changing over from warning lights to gauges?  I noticed that the temp. gauge was all the way over to the "H" even though the engine is cool. </span> <span style=": rgb248, 248, 252;"> </span> <span style=": rgb248, 248, 252;"> </span> <span style=": rgb248, 248, 252;">=================================================</span> <table width="99%" style="color: rgb0, 0, 0; font-size: 12px; : rgb248, 248, 252;"><t><tr><td ="BBquote" style="width: 1649.7px;"> neejah wrote: For posterity (fitting a '74/'76 cluster into a '72) - Pin<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>PCB Connections ('74-'76)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>Car ('72) 1 <span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Purple/White (Brake)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                              </span>Purple/White 2<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Red/White (Eng Temp)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                              </span>Red/White 3<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Blue/Red (Illumination)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                              </span>Blue/Red 4<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Black (-ve supply)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                                   </span> 5<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>White/Blue (Right Turn Ind)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>White/Blue 6<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Green/White (Left Turn Ind)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>Green/White 7<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Green/Black (High Beam Ind)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>Green/Black 8<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Black - Don't Splice (+12v)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>Black - Don't Splice (+12v) 9<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Yellow/White (Oil Pressure)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                         </span>White/Red 10<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>White/Red (Fuel)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                                   </span>Yellow/White 11<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Green/Red (No connection on PCB)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                    </span>Green/Red 12<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Yellow/White (Top RH Warning Lamp) 13<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Green (Btm RH Warning Lamp) 14<span apple-tab-span="Apple-tab-span" style="white-space: pre;">          </span>Red/Yellow Dash (-ve)<span apple-tab-span="Apple-tab-span" style="white-space: pre;">                              </span>Red/Yellow Dash (under hood conn.) Notes: Pin 14 & Pin 4 I routed to a new ground - the harness for pin 14 terminated in an underhood connection which didn't go anywhere. Pins 12 & 13 I haven't connected at the minute - I might use them for a shift light at some point in the future.......didn't really care about the fasten seat belt warning! Hopefully it might help someone in future......... Neil </td></tr></t></table><div style=": rgb248, 248, 252;">    Yes, this has been a huge help for me!......but I have a couple of corrections for the printed circuit board (D4GF 10C956 BA) 1974,1975, some 1976..... <div style=": rgb248, 248, 252;"> I am doing a retrofit of the instrument panel circuitry on my '76 (born on date 4-9-76) #9 Pin circuitry goes to the - (ground) side of the fuel gauge #10 Pin circuitry goes to the -(ground) side of the oil pressure gauge #12 Pin circuitry    there is an aprox. 1/4 break in the circuit on the PCB next to the plug in terminal block...I checked 2ea. D4GF 10C956 BA PCB's and the break is the same and in the same spot. The #12 circuit is the + (positive) for the Parking Brake light bulb...located in the top Right hand location of the instrument cluster. This one has me baffled...there is no other power source for the light bulb ( looking at the PCB) yet this light and the one below it (seat belts) share the same common ground circuit. #14 Pin circuitry goes to the - (ground) side of the brake warning light (pressure),parking break light and seat belt light ====================================================== This is the wiring information for the STANDARD instrument cluster (warning lights w/ Fuel and Temp. gauges) The pin numbers corresponds with the numbers on the terminal block that plugs into the printed circuit board (part # D6OF-10C956) I used the terminal block from my Torino (born on date 4-9-76) This information should prove to be valuable for those who are converting from a standard cluster to sport cluster ('74-'75-some '76) OR trouble shooting the standard PCB. '74-'75-some '76 LOCATION     COLOR(S)                               CIRCUIT INFORMATION PIN 1 Red w/ Yellow hatched marks        ground side (-) of brake (pressure) & oil pressure light socket PIN 2 Green w/ Yellow stripes                                           positive side (+) of fasten belt light socket PIN 3 Light Blue w/ Red stripe                                             positive side (+) of the dash light sockets PIN 4 Black                  ground side (-) of the dash,fasten belt,high beam and turn signal light sockets PIN 5 White w/ Light Blue stripe                         positive side (+) of the Right turn signal light socket PIN 6 Light Green w/ White stripe                         positive side (+) of the Left turn signal light socket PIN 7 Light Green w/ Black stripe                                positive side (+) of the High Beam light socket PIN 8 2 EA. wires Black      positive side input (female connection on PCB) instrument cluster voltage                                         regulator        PIN 9 Yellow w/ White stripe                                                                  ground side (-) of fuel gauge PIN 10 Light Green w/ Red stripe                 Pin's 10 and 11 both go to the alternator light socket. PIN 11 2 EA. wires #1 Dark Green               The measurement between pin's 10 and 11 is in Amps.            #2 Gray w/Yellow stripe                   The light is part of the curciut "loop' between pins 10&11     PIN 12   Red w/ White Stripe                                               ground side (-) of the temperature gauge PIN 13   White w/ Red stripe                                         ground side (-) of the oil pressure light socket PIN 14   Purple w/ White stripe                            positive side (+) of the Brake (pressure) light socket Unlike the sport cluster, there is no circuitry for the parking brake light with the standard cluster PCB  ======================================================== This is the wiring information for the sport instrument cluster. The pin numbers corresponds with the numbers on the terminal block that plugs into the printed circuit board (part # D4GF-10C956) This information should prove to be valuable for those who are converting from a standard cluster to sport cluster ('74-'75-some '76) OR trouble shooting the sport cluster PCB. '74-'75-some '76 LOCATION                         CIRCUIT INFORMATION PIN 1                      positive side (+) brake (pressure) light socket PIN 2                     ground side (-) temperature gauge PIN 3                      positive side (+) dash light sockets PIN 4                     ground side (-) all light sockets except parking brake and fasten belt PIN 5                     positive side (+) Right turn signal light socket PIN 6                     positive side (+) Left turn signal light socket PIN 7                     positive side (+) high beam light socket PIN 8                    positive side input (female connection on PCB) instrument cluster voltage regulator PIN 9                    ground side (-) fuel gauge PIN 10                  ground side (-) oil pressure gauge PIN 11                  NOT USED...NO CIRCUIT ON PRINTED CIRCUIT BOARD PIN 12                  positive side (+) parking brake light socket PIN 13                  positive side (+) fasten belt light socket PIN 14                  ground side (-) brake (pressure),parking brake and fasten belt light socket <span style=": rgb248, 248, 252;"> </span>

Ok fellas --   Yes, I know it ( again ) has been a while -- but -- I can finally give some attention to this, which I have.   I have examined the P.C. printed circuit ('74 Sport - there's a picture on page 1 of this thread ). I have also examined the wired pin connector on the car, which is believed to be original to the '76 S&H, and compared it to both the existing wiring schematic that I have, and the post above, which I've quoted.   It took me a little time to map out everything, but I think I have it fairly understood with a few exceptions.    I'm not sure how best to do this, so I will describe each pin "position" with respect to what is, what was, what is to be, and what should never be :)

I should note that the '74 Sport Gauge Cluster I have has 5 illumination lights, 1 (one) brake light positioned at the center top of the tachometer, 1 (one) high beam light positioned at the center bottom of the tachometer, 1 (one) each left and right turn signal indicators positioned on either side of the high beam indicator, 1 (one) Fasten Seat Belts light, and 1 "Low Fuel Economy" light. ( The previous post, nor other posts, say nothing about this "Low Fuel Economy" light indicator, so I'm not sure on this one. Nonetheless, the dash cover I have clearly has a green "Low Fuel Economy" light above the red "Fasten Seat Belts" light.   There is also not an "alternator light socket" on my cluster ? The previous post says that pins 10 / 11 both go to the alternator light socket. I don't have one of those lights, and you will read below about positions 10 and 11 and my confusion about what to do with them.


'74 Sport Gauge Cluster - hereafter '74 SGC
'76 Wiring Schematic / Car - hereafter '76 WS



POSITION 1
'74 SGC - positive(+) side of brake light
'76 WS - Circuit 640 - Red w/ Yellow Hash - seems to have an end at a "Low Vacuum Warning Indicator Lamp" and then also goes through the firewall blocks to the "Carburetor Throttle Emission Control Solenoid" and also to the "Distributor Modulator Valve". Additionally, inside the car, that circuit 640 is connected directly to the "Protection & Convenience, Seat Belt Warning Buzzer", and also ends at F-11 (fuse I think). ( the other side of the fuse is part of the coil + )    

Analysis : The wire from position 14 needs to be here instead.

POSITION 2
'74 SGC - negative (-) side of Temperature Gauge
'76 WS - Circuit 450 - Dark Green with Light Green Stripe - seems to be labeled as connected to the Seat Belt Warning Indicator Lamp on the P.C. and the Seat Belt Warning Indicator Switch.   (Is this the positive side for the Fasten Seat Belts light? )
Analysis : Move this wire to position 13, and move the wire from position 12 (negative temp gauge wire) to this spot.

POSITION 3
'74 SGC - positive (+) of the dash illumination lights
'76 WS - Circuit 19 - Blue with Red Stripe - positive (+) from fuse

Analysis - no changes needed

POSITION 4
'74 SGC - negative (-) of dash illumination, high beam indicator light, and turn signal indicator lights
'76 WS - Circuit 57 - Black - negative (-) connected to a lot of other negative wires and ground.

Analysis - no changes needed

POSITION 5
'74 SGC - positive (+) of the Right Signal Indicator
'76 WS - Circuit 2 - White w/ Blue Stripe - Right Turn Signal positive (+)

Analysis - no changes needed

POSITION 6
'74 SGC - positive (+) of the Left Signal Indicator
'76 WS - Circuit 3 - Light Green w/ White Stripe - Left Turn Signal positive (+)

Analysis - no changes needed

POSITION 7
'74 SGC - positive (+) of the High Beam on Indicator
'76 WS - Circuit 12 - Light Green w/ Black Stripe - High Beam positive(+)

Analysis - no changes needed

POSITION 8
'74 SGC - Seems to be the common POSITIVE (+) to the gauges ( Fuel, Oil Pressure, Temperature )
'76 WS - Circuit 297 ( There is also the number 48 there ? I can provide pic if desired ) - Black w/ Blue Stripe is what is actually in the car. The schematic says it should be a Black w / Light Green Hash ?? - but it seems to be part of the circuit which comes from the key switch, and is off when the key is in the "start" position, and on when the key is in any of the other positions ( except "Off")

Analysis - no changes needed

POSITION 9
'74 SGC - negative(-) side of the Fuel Gauge
'76 WS - Circuit 29 - Yellow w/ White Stripe - Fuel circuit

Analysis - no changes needed

POSITION 10
'74 SGC - negative (-) side of the Oil Pressure Gauge
'76 WS - Circuit 904 - Green w/ Red Stripe - This circuit seems to carry the voltage to the regulator, and originally went to the coil then also?   It is connected to the (Green w/ Red Hash ?) wire from position 11.

Analysis - The wire from position 13 (White w/ Red Stripe) needs to be moved here, but I'm not sure where this wire should be moved to.

POSITION 11
'74 SGC - There is NOTHING here - not even a copper tab on the P.C.
'76 WS - Circuits 904 AND 687.   Circuit 687 is a Grey w/ Yellow Stripe wire which goes to the ignition switch. Circuit 904 ends up connected to the wire from position 10, so again this is confusing as to what I should do with it.

Analysis - I have no idea what to do here ?   

POSITION 12
'74 SGC - positive(+) side of the "Low Fuel Economy" light - but NOTE the picture : there is a BREAK in the printed circuit ??   WHY ??
'76 WS - Circuit 39 - Red w/ White Stripe - negative (-) to the Temperature sending unit.

Analysis - move the Red w/ White Stripe to position 2 to match the printed circuits / cluster.   Not sure what wire to move here ?

POSITION 13
'74 SGC - positive(+) side of the Fasten Seat Belts light
'76 WS - Circuit 31 - White w/ Red Stripe - negative (-) to the Oil Pressure Sending unit.

Analysis - move the White w/ Red Stripe to position 10 to match the printed circuits / cluster.   The Dark Green w/ Light Green stripe wire from position 2 moves here

POSITION 14
'74 SGC - seems to be the common (-) negative for the lights for the Brake light, the Low Fuel Economy light, and the Fasten Seat Belts light.
'76 WS - Circuit 977 - Purple w/ White Stripe - positive(+) side of the brake light

Analysis: Move the wire to position 1.   I'm not sure if I should swap this with the wire from position 1 though, but I think I should.


In summary, I think that
Wires 1 and 14 can be swapped.
Wire 2 moves to position 13
Wires 3-9 are correct and can stay.
Wire 10 gets moved to ??
Wire 11 gets moved to ??
Wire 12 moves to position 2
Wire 13 moves to position 10.
Wire 14 (again) is swapped with 1.

I really appreciate anyone who reads this and offers advice or corrections.    I will supply any pictures or further descriptions that are requested.

PS. as far as the Tachometer, rather than punch a hole through the firewall, or chop the end off of the harness that California Johnny sent, I will find a plug that I will simply connect to that end, and then run the tachometer wires through the existing firewall blocks ( C-401 or C-402 ) in holes / positions which are unused.   I will also hook up the ammeter wires in similar fashion.   Those items, and the clock tap are separate from the rest of the instrument cluster which I'm discussing above.




Edited by squarethumps - 28-November-2020 at 5:20AM

yes that's right .. I did the same thing with my P.C. by tracing the connections and using your advice that the gauges share a common positive, while all the lights share a common negative, this makes a lot of sense.

It was those two wires ( 3 really ) the green with the red stripe and the grey with the yellow stripe that are the confusing ones. I've moved those to the spots where there are basically no connections to the P.C. ( no loop either ) I'm not sure if this is 100% correct as we will see.

Soooooooo ....   I made those changes as follows :

wire 1 swapped with wire 14
wire 2 moved to position 13
wire 3 - 9 no changes
wire 10 moved to position 11 ( the dead spot )
wire 11 moved to position 12 ( basically another dead spot )
wire 12 moved to position 2
wire 13 moved to position 10
wire 14 (as above) swapped with wire 1.

I plugged it in aaaaannnd !!!!    weeeell ..

I decided to test the cluster illumination lights first ( the headlight switch already works to turn on the illumination lights behind the climate control, and the dome light works from that switch too )

it looks like ONE of the cluster illumination lights is working .. the one that is over by the ammeter. soooo ... ( sorry .. I started investigating ) ...
So I had bought and installed new LED backlights .... turns out that these lights only work ONE way, even though they fit both ways ( like . 180 degrees out ) .. so ... so far I've found one defective LED light, and 3 of the sockets are working !! So I'm going to keep playing and testing things and I'll provide an update soon .

I also tested the Oil Pressure gauge by just grounding the wire in the engine bay directly to the engine block / ground, and the oil gauge went up to just below 90, which I imagine might be just about as far as that old gauge can go. I'm calling it a success and working !

I tested the temperature gauge ... it's not working, at least when I ground the wire at the same connector in the engine bay as the oil pressure wire ( the oil pressure, coil wire, and temperature wire all travel through the same connector in the engine bay )   so I will test this by grounding out the terminal wire directly behind the cluster 14 pin connector wire in position 2 and see if the gauge moves.

so ... there has been some success and I'll keep updating

Here is what I discovered doing the standard to sport cluster change.  I've done it to all 5 of my Gran Torino's. 

so .. since the illumination lights are working I started testing the gauges.

I suppose I should also note that when I turn on the key I don't get the buzzer, and none of the other lights light up ( fasten seat belts I would expect ) so that will need to be sorted.

The oil pressure gauge works perfectly. I grounded out the wire all the way at the end where it actually connects to the sending unit and the gauge spiked up. 1 down ..a bunch to go !

The temperature gauge itself works but something is up. I ran a negative from the battery directly to negative side of the gauge post, and it works.   Then I tested it on the back of the connector by jamming the ground wire directly into the #2 position wire ( which is now the White with Red stripe wire ), and again the gauge moves. This tells me the problem is not in the cluster or gauge, but in the White w/ Red stripe wire somewhere between the cluster and that terminal end in the engine bay. (Is there a fuse ? )   In any case, at least the gauge and cluster P.C. works.   Coincidental that you had an open circuit there too Steve M.   I will investigate and see what I can figure out.


I will probably test the fuel gauge next.

I used this to get the wires to double check how I was going to get my wires to the correct gauges. Interesting enough,  my car doesn't have the microswitch for the e-brake. The connector is there should I wish to install it 

Love the LEDs!

Hey John, 

I'm digging through a folder of old papers on my car to find this stuff. The idea of doing another one is in the back of my mind. 

Steve M. wrote: I'm digging through a folder of old papers on my car to find this stuff. The idea of doing another one is in the back of my mind.  On my '73, we cut the rusted roof off and installed one from a '78 T-bird with T-tops. There was a lot of beers on that one.

Oh WOW T-TOPS on a torino !! that would be cool !! got pics ?

i don't remember what the issue was but i swapped the regulators and it worked better? i think it's more for the fuel gauge than anything?