Lynx scout car wiring problems (Ford)

[lynx42]

This is the old circuit breaker, which I had marked the wires for easy re-connection but it has been quite s few years (like 30) and I do not have it correct.

Lynx resister unit 025.jpg

This is the 12volt to 6 volt resistance coil.

Lynx resister unit 022.jpg

This is the resistance from 6 volts to 4.6 volts for the coil.

Lynx resister unit 027.jpg

What I do not understand is that the mounting bolts earth out the resistance as the mounting bolt goes through the casing of the coil cover which is on an insulated block. How does this work or am I missing something as I an not an electrical engineer.

Lynx resister unit 018.jpg

The current comes off the 6 volt resistance coil via a metal strip which links the two further coil voltage reducers to the mounting bolt which goes to earth.

Would that not cause a short circuit?

Lynx resister unit 021.jpg

Thanks for your help.

Regards Rick

[Peter Duggan]

Rick,

Glad that your circuit breaker assembly showed up in such good shape. I will offer my two cents worth, but recognize that my electrical knowledge is even more limited.

The schematics for the Lynx 11 show only one connection on the right hand side of the circuit, and that is for wire 20, which is for the temperature gauge. And that connection appears to be to the second terminal from the top. For the mounting bolt on the upper right hand corner, I simply started it under the top plate, avoiding any short circuit possibility.

I was going to wait until I had the opportunity to visit and view the Lynx 11 at the Canadian War Museum and confirm my assumption. Also hoping that Rob Love may pipe up and offer his thoughts based on his knowledge and access to the Lynx in Shilo.

Glad that you spoke up, my assumptions are just that, assumptions.

Peter

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[rob love]

I'm looking at the resiter package on ours now and it has the screw in the top corner. No idea why it does not ground.

It is wire no 22 for the temp gauge according to my manual. Wire 20 is for the LH fuel sending unit to the fuel gauge switch.

I have a job on the go today, but hopefully I'll find some time in the next day or two to pull the guard and do some circuit checking. My wire 22 is coming from the right side of the circuit divider. I should think the coil would be what came off the small resister.

When I re-wired the lynx, I remember thinking it was funny that they ran 12 volts from the engine compartment all the way up to the dash, to then run the 12 volts back to the divider and then run it back up to the front again and twice at that. Once for the 6 volt electrical gauge, and once for the remainder of the gauges. I am running a 12 volt gauge so have the one extra wire tied off at the divider unit.

I note that where your wire 20 (22?) comes off the resister now, it might as well be off the screw one lower. There is no voltage drop from the bottom resister to the terminal that wire is coming from. If the mounting screw was fastened to the top corner and grounded out, it would merely burn out the top resister....it would not effect the voltage at the first terminal. Of course, the race would be what burns out first...the top resister, the bottom resister, the circuit breaker, or some piece of wiring.

More to follow.

[Colin Alford]

Gents,

I am certainly not an electrical engineer and unlike the three of you, I have never even touched a Ford Lynx.

I do however have access to SC-F3 and a few months ago I was seriously studying the wiring diagrams to help diagnose a "no power to coil" issue in a Windsor Carrier which uses many of the same electrical components.

I am surprised that there appear to be so many different versions of the wiring diagram. It appears that Peter's image is the same as that on page N-1 of SC-F3 so I presume that it is his source. Rob/Rick - What manuals are you referencing?

I have attached a few images from SC-F3 but I find that I struggle trying to get decent resolution in the images but keep them small enough to attach to a post.

On page N-2 of SC-F3 there is a second wiring diagram that I think will be most useful to this conversation. This type of diagram probably has a proper name but of interest is that it shows the voltages, resistances and grounding points.

It shows a ground point at the 6 volt side of the voltage divider. Is this the proof to alleviate Rick's concern about a potential short circuit caused by the mounting bolt passing through the top end of the voltage divider? (again I am not an electrical engineer and understand Rick's concern)

Page N-3 has an image of the voltage divider in-situ in the vehicle and should help determine which wire connects to which terminal.

I have also included a close-up of the circuit breaker/voltage divider and the other half of the legend from the diagram on page N-1 of SC-F3 to complement Peter's images

If any of you would like higher resolution pictures please send a PM with your email address and I can send them to you

[Mike K]

Rick

I think you have misunderstood the circuit . If you study the wiring diagram, the coil 4 Volts feed comes off the larger resistor . The smaller resistors feed the instruments . Mike

[Colin Alford]

Rick,

I will echo Mike's comment that I think you previously misunderstood which components were performing which task on the Circuit Breaker/Ignition Resistor/Voltage Divider assembly.

I think if you have a good study on the newly provided wiring diagrams that it should make sense (I can send higher resolution images if you would like).

I have also sorted out the question of the mounting bolt providing a path to ground and therefore a short circuit. The mounting bolt is designed to provide the ground and therefore make the Voltage Divider work! I really had no idea how this functioned until I googled "Voltage Divider"

See:
https://en.wikipedia.org/wiki/Voltage_divider

[Peter Duggan]

Rick,

Thanks for raising this question about the mounting of the circuit breaker assembly. I was mistaken about how it functioned and how it should be mounted.

Colin, Mike and Rob,

Thanks for sharing your time and knowledge. These are the benefits that I was seeking when I first joined this forum. A great group of people.

Thanks again, Peter

[Tony Wheeler]

Originally Posted by Mike Kelly

If you study the wiring diagram, the coil 4 Volts feed comes off the larger resistor . The smaller resistors feed the instruments .

Exactly.

Lynx resister unit 013.jpg

I notice one wiring diagram is for ammeter and the other is for battery condition indicator (ie. voltmeter). It's optional of course but something to be aware of when wiring up.

[Tony Wheeler]

Originally Posted by lynx42

What I do not understand is that the mounting bolts earth out the resistance as the mounting bolt goes through the casing of the coil cover which is on an insulated block.....Would that not cause a short circuit?

Never fear Rick, your prized NOS unit will not go up in smoke! Those paired resistors are not ordinary ignition resistors. If you look closely you'll see they use much longer wire, which means far greater resistance. That limits the current flowing to earth. For example, if each one is 10 ohm, the total resistance is 20 ohm, which means the current flowing to earth will be a tiny 0.6 amps (V = IR gives 12 = 0.6 x 20). Of course, as the voltage drops evenly from 12V to zero, you can tap off halfway to get 6V.

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