"S**T!" It's a Resistor Wire- Wiper Switch to Gauge Cluster?

What is the purpose of the resistor wire (black/green) which runs between the wiper-washer switch (has 8 wires + the resistor wire) and the 12 pin dash cluster connector? ('73 Mach 1- Q- Code, has factory Tach but that's a separate question) It is a black single strand wire, which has green lettering on it "resistor wire do not cut or splice." I noticed the lettering AFTER I cut it to make a repair to it. (Insulation was deteriorated in one area.) I overlapped the wires in a butt connector and mechanically crimped them together. Is this okay?

Find out and let us know. I'm betting it will be fine.

What is the purpose of the resistor wire (black/green) which runs between the wiper-washer switch (has 8 wires + the resistor wire) and the 12 pin dash cluster connector? ('73 Mach 1- Q- Code, has factory Tach but that's a separate question) It is a black single strand wire, which has green lettering on it "resistor wire do not cut or splice." I noticed the lettering AFTER I cut it to make a repair to it. (Insulation was deteriorated in one area.) I overlapped the wires in a butt connector and mechanically crimped them together. Is this okay?

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What is the purpose of this resistor wire?...other that to provide resistance, of course. Why resistance is this situation...wiper switch to gauge cluster...

Midlife can better answer this question but this is my thoughts here. I believe that it is supplying power to the CVR for your gauges. From what I can tell is that the CVR requires 12v on its input and outputs between 0 to 6 volts to the gauges. Since the voltage is not always 12v in the system (when battery is charging it's about 13.7v) this resistance wire is used to try to keep it as near 12v as possible. I don't think that it will break anything by splicing but could possibly affect the accuracy of the gauges. A easy check would be to check the voltage at the CVR input while the motor is running. This CVR appears to be a thermal switch so higher or lower voltage will affect its switching frequency. Again this is my thoughts here so don't take it as gospel.

As long as it is good crimp connection it should not be a problem The splice should yield a really, really near zero ohms resistance. As far as gauge accuracy, they will be as inaccurate as they were before. Chuck

The resistance wire is to reduce the voltage to the regulator to 7 or 8 volts, which reduces the load on the contacts, heating coil, and bi-metal strip in the instrument voltage regulator. A 1/4 inch overlap will likely increase the voltage to the IVR by 0.1 or 0.2 volts, and should not be a problem.

Dammit guys, you beat me to it! Yes, that wire provides reduced ACC power to the CVR on the dash cluster. A good crimp connector will get you back in business, although it is a single strand of nichrome wire and that is very hard to crimp positively. It's best to crimp it with another multi-stranded wire on each end of the butt splice and keep the extra wire out of harm's way.

Midlife can better answer this question but this is my thoughts here. I believe that it is supplying power to the CVR for your gauges. From what I can tell is that the CVR requires 12v on its input and outputs between 0 to 6 volts to the gauges. Since the voltage is not always 12v in the system (when battery is charging it's about 13.7v) this resistance wire is used to try to keep it as near 12v as possible. I don't think that it will break anything by splicing but could possibly affect the accuracy of the gauges. A easy check would be to check the voltage at the CVR input while the motor is running. This CVR appears to be a thermal switch so higher or lower voltage will affect its switching frequency. Again this is my thoughts here so don't take it as gospel.

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Thanks jbojo...when you say it may "affect the accuracy of the gauges" do you mean the gas gauge, as it's the only gauge in this cluster. Tach, gas gauge, and Speedo are the only ones in this cluster. If that's what you mean I will closely observe at fill up time...

As long as it is good crimp connection it should not be a problem The splice should yield a really, really near zero ohms resistance. As far as gauge accuracy, they will be as inaccurate as they were before. Chuck

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Thanks c9zx,...since the single strand wire was such a thin gauge, I stripped it back about an inch on each end and sent each wire all the way through the butt connector (red) so they would not only get crimped by the connector but would also get squeezed together. I then slid some shrink tubing over it and sealed it up. Hope it works!

The resistance wire is to reduce the voltage to the regulator to 7 or 8 volts, which reduces the load on the contacts, heating coil, and bi-metal strip in the instrument voltage regulator. A 1/4 inch overlap will likely increase the voltage to the IVR by 0.1 or 0.2 volts, and should not be a problem.

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Thanks Don...usually with a butt connector I wouldn't have an overlap at all but since the single strand wire was such a thin gauge, I stripped it back about an inch on each end and sent each wire all the way through the butt connector (red) so they would not only get crimped by the connector but would also get squeezed together. I then slid some shrink tubing over it and sealed it up. How will that effect the voltage?...still okay?

Dammit guys, you beat me to it! Yes, that wire provides reduced ACC power to the CVR on the dash cluster. A good crimp connector will get you back in business, although it is a single strand of nichrome wire and that is very hard to crimp positively. It's best to crimp it with another multi-stranded wire on each end of the butt splice and keep the extra wire out of harm's way.

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midlife, to you I must give the greatest thanks...for some reason I cannot stop looking at your response(s)...

If you have a center console gage cluster it would affect them too. Oil and temp for sure, not sure about the ammeter though.

Even with the longer overlap you should still be OK. The IVR will probably wear out a little faster, so you might want to consider a solid state electronic regulator.

Midlife is correct, it's not easy to keep nichrome wire crimped. It's not easy to solder, either. Silver solder and a good liquid flux should work on the crimped connection, if it seems like you're not getting voltage to the IVR.

Dammit guys, you beat me to it! Yes, that wire provides reduced ACC power to the CVR on the dash cluster. A good crimp connector will get you back in business, although it is a single strand of nichrome wire and that is very hard to crimp positively. It's best to crimp it with another multi-stranded wire on each end of the butt splice and keep the extra wire out of harm's way.

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Could you possibly show me (pic) where the CVR is and what it is? Clarify stranded wire crimping technique you spoke of... Don spoke of an IVR, same thing? What do the initials stand for? Don says consider a solid state electronic regulator?...replacing IVR/CVR or in addition to?...cornfused :huh:

CVR = Constant Voltage Regulator

aka

IVR = Instrument Voltage Regulator.

Picture of one can be found here:

http://www.ohiomustang.com/store/order_page.asp?itemid=3221

Provides a pulsed 5 vdc for your instrument gauges. Original one was mechanical, newer one that Don mentions is solid state and more reliable.

The link shows the new solid state one, what does the old mechanical one look like and where would I look to find it, behind the dash? I can just buy the new one and install it where the old one is located?...that's all?...sounds easy, is it?


oh and I just watched your restoration video...really nice job! We really do get to know every inch of our cars, don't we?

The link shows the new solid state one, what does the old mechanical one look like and where would I look to find it, behind the dash? I can just buy the new one and install it where the old one is located?...that's all?...sounds easy, is it?


oh and I just watched your restoration video...really nice job! We really do get to know every inch of our cars, don't we?

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Look at Midlife's post #13 here:

http://www.7173mustangs.com/thread-can-the-instrument-cluster-be-hard-wired?page=2

The third picture shows it behind where the tach would be mounted. The little rectangular box. Not sure if the old mechanical ones are produced anymore.

Yeah I learned a lot from my restoration.

The link shows the new solid state one, what does the old mechanical one look like and where would I look to find it, behind the dash? I can just buy the new one and install it where the old one is located?...that's all?...sounds easy, is it?


oh and I just watched your restoration video...really nice job! We really do get to know every inch of our cars, don't we?

Click to expand...

Look at Midlife's post #13 here:

http://www.7173mustangs.com/thread-can-the-instrument-cluster-be-hard-wired?page=2

The third picture shows it behind where the tach would be mounted. The little rectangular box. Not sure if the old mechanical ones are produced anymore.

Yeah I learned a lot from my restoration.

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...so if I understand correctly, I cut/repaired my resistor wire which runs from the wiper switch to the dash cluster connector which ultimately connects to the CVR/IVR, whose purpose is to send pulsed dc voltage to my instrument gauges.

...as a preventative measure, it was suggested to change out the mechanical CVR/IVR to a solid state one which you provides a link for.

(http://www.ohiomustang.com/store/order_p...temid=3221)

...according to midlife's post, if I'm understanding correctly, I could buck up the $25 and just attach the solid state replacement in the original position and the circuit board would then be able to reconnect to the new CVR/IVR with the "battery snaps" on the circuit board and the "battery snaps" I think I see on the solid state replacement????

...my next somewhat obvious question...what's the chance the circuit board breaks when I attempt to "unsnap" it from the original (hasn't been unsnapped in 32 years) CVR/IVR???? Did you happen to notice my quote at the bottom of my posts? "The worst enemy of good is better" (taught to me by an orthopaedic surgeon I used to work with) I always have to remind myself of that quote, as I like to do things the best I can. Nonetheless, is it a dangerous move?...and do you have any suggestions?...tiny flathead screwdriver as a prybar so I'm not pulling on circuit board material???? :huh:

You're experience and willingness to share advice is invaluable...


...ordered it.

I changed mine out after 40 yrs with no issues. Your comment about new is better I agree with. If I were to do it over again I would leave the old one on until it breaks. My fuel gauge is not as accurate now but it could also be due to the Fuel level gauge that I replaced in the tank. I replaced it originally because I did not want to go into it again if the old one failed.

...I think you meant to type "...good is better." Yeah, that's always the risk when replacing a few parts at the same time. Maybe I'll take your/my advice and hold on to the new solid state part until I have a problem instead of moving ahead too fast. Thank you again!!!

Well, if you break the circuit card, you can contact me and I can sell you production unit #0001 of the hard-wired dash cluster.