Lynx scout car wiring problems (Ford)
 

Thank you Peter Duggan for your lead to a new resistance/circuit box unit for my Canadian FORD lynx. The new old stock unit arrived today and I am rapt. I had tried to rebuild the 1943 unit without complete success.

I am in need of help to work out what goes where.

The Ford Lynx runs 3 different voltages. 12vols for the starter, generator, lights and radios from 2 x 6volt batteries. The resistance block then reduces the voltage to 6 volts for the gauges etc and then the voltage is further reduced to 4.6volts for the coil.

This is the wiring diagram from the manual which does not give a clear direction to or from the actual resistance/circuit breaker unit

Attachment 79901

This is the box as it arrived.

Attachment 79902

This is the sealed waxed paper wrapping.

Attachment 79903

The unit in 2016 air.

Attachment 79904

The complete unit.

Attachment 79905

In the next post I will explain my problem.

Thanks Rick.

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.

Attachment 79907

This is the 12volt to 6 volt resistance coil.

Attachment 79906

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

Attachment 79908

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.

Attachment 79909

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?

Attachment 79910

Thanks for your help.

Regards Rick

Same quandry
 

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

Attachment 79920 Attachment 79922

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.

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

wiring
 

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

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

Thanks
 

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

We are getting there.
 

Thank you Peter, Rob, Mike and Colin. We're getting somewhere. I was completely stumped at the start but now seem to understand a bit better.(??)

I have sent you a PM Colin, for better resolution copies of the SC-F3 wiring system.

The early Lynx manual Sc-F1 and F2,(mine) is hard to understand and as well, all wires are BLACK and not numbered.

Thanks again, I knew MLU members would come up with the answers.
Regards Rick.

Condensers and filters
 

Next question, what is with all the condensers on everything and filters as well. Is it necessary to have every one or can the vehicle operate without some of them?

Can I use any old (new) condenser or do they have a rated action?

I guess that they are there to cut down radio interference etc, so are they really necessary if I am not using a working WWII radio? I have a No.11 fitted but it is only there for looks.

Regards Rick.

You can leave them all off Rick

Colin

Good information on the voltage divider. I have learned something new today. When I get a chance I'll have to check the Lynx and make sure it was wired properly.

Old dog now has a new trick.

Exactly.

Attachment 79966

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.

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.

Attachment 79967 Attachment 79968