Testing the electrical system and due diligence

[facultyofmusic]

While reading juddster's post this morning I was reminded of many other electrical system related mishaps I've read on the forum over the years, from crossed light wires to wrong pins on RF harness connectors. My question for experienced folks is this: How much testing do you do of your electrical system before hooking it up to the battery? What about before engine first start? Any advice you'd give to a newbie who've never worked on vehicle electronics? Any parts of the car to pay special attention to? Any areas that would be a pain in the *** to debug after the engine is in? What about problem prevention down the line such as wires rubbing on the frame and wearing out protective coatings?

[narly1]

I guess it all depends on your comfort level with this aspect of the build. Just like any other part of the project chunk it out into manageable sub-tasks. It's easy to break it down to one circuit at a time. By only running one fuse at a time in the block you can isolate, power and test its associated circuit. If you don't own a multimeter and a circuit tester buy them now. Just work slow and methodical and draw the circuits out and label them with their associated colours so you know what's what.

On the subject of wiring protection you gain a sixth sense for what and when it's needed. Anywhere there's a sharp edge or turn you need something. Tie your wiring down so that it's not flopping around and chafing against stuff. For reference take a look at how things are done in your daily driver or go for a wrecking yard tour. That would be my advice.

Earl

[NAZ]

I wring-out the circuits making sure they are landed correctly. Then just throw the switch and roll the dice. That's what fuses are for.

And to think, the US Army used to have me take apart nuclear warheads and repair them when I was a teenager. Yup, one slip and instant vaporization.

[J R Jones]

I wring-out the circuits making sure they are landed correctly. Then just throw the switch and roll the dice. That's what fuses are for.

And to think, the US Army used to have me take apart nuclear warheads and repair them when I was a teenager. Yup, one slip and instant vaporization.

On fighter/interceptors there were three levels of maintenance: Organizational, Intermediate and Depot. The F106 had the MA-1 integrated system, communications, radar, computer, weapons control, and navigation. A nightmare. Part of the test run-ups after Intermediate and Depot maintenance was a "smoke" test. Unlike at the Vatican, we prayed for no smoke.

In Asia turning an "Intermediate" for alert duty, everyone was working simultaneously. 2AM grave shift on the run-up pad I am on the wing working in the Nav compartment plugged into the intercom as the crew chief in the cockpit is at full-mil, canopy down. He calmly announces, hang on for "burner". There is an explosion of thrust and the aircraft instantly stretched the restraint cables three inches, lurching from 16,000 to 24.500lbf of thrust. One tends to loose one's concentration when that happens.
jim

F106 intercpt 2.jpg

[NAZ]

On fighter/interceptors there were three levels of maintenance: Organizational, Intermediate and Depot. The F106 had the MA-1 integrated system, communications, radar, computer, weapons control, and navigation. A nightmare. Part of the test run-ups after Intermediate and Depot maintenance was a "smoke" test. Unlike at the Vatican, we prayed for no smoke.

In Asia turning an "Intermediate" for alert duty, everyone was working simultaneously. 2AM grave shift on the run-up pad I am on the wing working in the Nav compartment plugged into the intercom as the crew chief in the cockpit is at full-mil, canopy down. He calmly announces, hang on for "burner". There is an explosion of thrust and the aircraft instantly stretched the restraint cables three inches, lurching from 16,000 to 24.500lbf of thrust. One tends to loose one's concentration when that happens.


jim

F106 intercpt 2.jpg

Jim, that's a max pucker factor for sure.

The military can be an exciting career. It was the best job I ever had, and most unique. Sometimes I miss it but my job was eliminated in 1979 with the SALT II treaty.

[txboiler]

On fighter/interceptors there were three levels of maintenance: Organizational, Intermediate and Depot. The F106 had the MA-1 integrated system, communications, radar, computer, weapons control, and navigation. A nightmare. Part of the test run-ups after Intermediate and Depot maintenance was a "smoke" test. Unlike at the Vatican, we prayed for no smoke.

jim

F106 intercpt 2.jpg

The story about having your head in the navy compartment and plane lurching under full power; not withstanding, the photo of the F-106 and the Russian Bear is equally impressive

Thanks for sharing both.

[J R Jones]

The story about having your head in the navy compartment and plane lurching under full power; not withstanding, the photo of the F-106 and the Russian Bear is equally impressive

Thanks for sharing both.

txboiler,
Thank you. We had alert cells on King Salmon Is and down the road from Fairbanks. We scrambled at least twice per week.
We were snipers, we knew when they crossed into our airspace and could lock-on from 32 miles away. We had 1525 MPH available, they were sitting ducks. The routine called for a 35mm photo in formation and escort them out of our airspace. The Russians were entertained and bird salutes from the crew were common. On one occasion the Russians held Playboy centerfolds up to the cockpit glass.
jim

[Jeff Kleiner]

I test everything using a low amperage battery charger in place of the battery. If anything is amiss the 5 amps isn’t enough to hurt anything.

Jeff

[GTBradley]

I found my master cutoff switch to be both handy and peace of mind. Mine is a true cutoff so if I ever have an electrical short I can isolate the battery in short order. You’ll do lots of electrical work throughout the build and it’s nice to be able to just flip the switch and go to work splicing wires, etc. Incidentally, the Coyote doesn’t stop running if you turn off the master.

[facultyofmusic]

I found my master cutoff switch to be both handy and peace of mind. Mine is a true cutoff so if I ever have an electrical short I can isolate the battery in short order. You’ll do lots of electrical work throughout the build and it’s nice to be able to just flip the switch and go to work splicing wires, etc. Incidentally, the Coyote doesn’t stop running if you turn of the master.

It doesn't?

[edwardb]

...Incidentally, the Coyote doesn’t stop running if you turn of the master.

It doesn't?

There are several variables. But bottom line in most cases that's not unique to the Coyote. Once the engine is running, the alternator can backfeed the electrical system and the engine can keep running even when the battery is disconnected. There are master disconnect versions that have a connection for the alternator so it too is shut off. Required by some (all?) race sanctioning bodies. This is one example: https://www.summitracing.com/parts/mor-74108.

[NAZ]

There are several variables. But bottom line in most cases that's not unique to the Coyote. Once the engine is running, the alternator can backfeed the electrical system and the engine can keep running even when the battery is disconnected. There are master disconnect versions that have a connection for the alternator so it too is shut off. Required by some (all?) race sanctioning bodies. This is one example: https://www.summitracing.com/parts/mor-74108.

Exactly! And one of the tech checks at an NHRA event is they will have you start the engine and the inspector turns off your master to verify the engine stops instantly.

The other thing you can do is land the alternator hot on the battery side of your master so the alternator feeds the battery direct. That way when you open the master circuit the alternator only feeds the battery. The bonus is there is no sudden spike when the existing load on the alternator is cut.

On a conventional ignition car, the radiator fan can backfeed power and keep the engine running for several seconds. Running the fan off a relay prevents this.

[Jessew]

I found my master cutoff switch to be both handy and peace of mind. Mine is a true cutoff so if I ever have an electrical short I can isolate the battery in short order. You’ll do lots of electrical work throughout the build and it’s nice to be able to just flip the switch and go to work splicing wires, etc. Incidentally, the Coyote doesn’t stop running if you turn off the master.

This is one reason to have your cut off on the ground side.

[NAZ]

This is one reason to have your cut off on the ground side.

On many cars, the alternator is grounded either through the engine or with a separate ground wire to the chassis. It will continue to feed the electrical system even with the negative battery cable disconnected. Before cars were computerized, disconnecting the battery on a running engine was a shade tree mechanic's way to check for a failed alternator.

[J R Jones]

NAZ, Yeah I get chills at the smell of jet fuel. I told my son that I don't want a 21 gun salute, I want a recording of a fighter taking off in afterburner, full volume.
My last eight months was doing development on the 106. We replaced the tactical nuc with the M61A1 20mm Gatling cannon. That was pretty cool.
I was TDY or reassigned every six months for 4 years and liked it, but could not see myself as a lifer. With the exception of two military transports, I had to find my way all over the world at 18 to 22 years, and thought nothing of it. Maybe I wasn't THAT bright; it would not have been a bad career.

It does not end well for old fighters. They were downgraded to Air National Guard in the eighties and used as drone targets; then the desert. Sad. NASA had one with two additional engines on the wings, flying chase for the space shuttle.
jim

[GTBradley]

I once flew a plane from New Century Airport near KC to Sedalia, Missouri. It had just come out of maintenance and would not start, so we got a power cart on it and it started right up. I flew all the way with no issues. After landing and pulling power back to taxi speed the field collapsed on the alternator and all instruments died. Engine kept going but did not restart after shutdown. When we pulled the access panel where the battery should be there was nothing but dangling battery cables. The power plant is designed to not be dependent on the electrical system for good reason. This can be handy in cars too, race cars notwithstanding.

[Steve in Snohomish]

Just redid the whole wire harness for my 67 Firebird. Used the battery and started to check systems. No issues as far as voltage/amps. Thing I did find out is make sure all your grounds are good. Had issues with turn indicators lighting up when headlights are on. Finally had to run a dedicated ground from gauge cluster to frame to solve the problem.

[phileas_fogg]

Back to the OP's original question: I verified the wires on each side of each Ron Francis connector matched up. I connected each wire where it should go, taking each step one at a time. Hooked it to the battery and verified each circuit in one go. It was easy-peasy, even with a push button start.

When running wires, everything is in a loom as far as feasible, and every pass through gets a grommet of some sort.


John

[facultyofmusic]

Thanks for the replies everyone! Sounds like I shouldn't worry too much about testing every little detail. I plan to do just some simple continuity testing after I have my dashboard installed to make sure the correct things are getting turned on. I'll let the fuses do the job for everything else.

[michael everson]

I take the positive cable off the battery and jump it with a 10 amp fuse. Its large enough to handle each circuit at a time without blowing. If everything checks out i put the positive back on the battery.
mike

[Alan_C]

During the wiring of my MK4, as I added wiring, with the battery disconnected I would check for shorts between 12V side and ground. This worked to a point, but found that as soon as you connect the front and rear lighting, it look like you have a short to ground in the system. Turns out the headlights, brake lights, turn signal lights, etc. their filaments, when cold, have a very low resistance, thus the appearance of a short to ground. So if you are going to use a DMM to check resistance as you go, add the lighting last, ask me how I know.

[Avalanche325]

As soon as the engine starts, the alternator is the power supply for the electrical system.

[facultyofmusic]

Hmm... this maybe problematic. I've put the alternator on the "switched" end of the battery cut-off switch, which means if I cut the switch, the alternator will still power the rest of the system that's supposed to be cut from electrical power when the switch opens.

[NAZ]

Hmm... this maybe problematic. I've put the alternator on the "switched" end of the battery cut-off switch, which means if I cut the switch, the alternator will still power the rest of the system that's supposed to be cut from electrical power when the switch opens.

Yes, that really kind of defeats the purpose of a "MASTER" switch. As mentioned above, either replace your current switch with one that incorporates a switched alternator hot or land the alternator hot on the battery side of the switch (that's how I wire mine).

[GTBradley]

Yes, that really kind of defeats the purpose of a "MASTER" switch. As mentioned above, either replace your current switch with one that incorporates a switched alternator hot or land the alternator hot on the battery side of the switch (that's how I wire mine).

I don’t see the advantage in that approach. To me, they are two separate electrical systems, one is isolated by turning off the battery cutoff switch and the other by shutting off the ignition switch. Plus, the battery cutoff switch is effectively a master switch that prevents the engine from starting.

[NAZ]

GT, most cars on the road simply control the power distribution with the ignition switch -- there is no "Master Switch". I'll submit that is really all that is needed. Adding a master switch adds complexity to the system and is superfluous for most applications. However, many racing sanctioning bodies require a master switch that disconnects all power from the battery, and alternator if equipped with one. During the tech inspection you car may be tested to ensure opening the master will shut off all power and kill the engine. If you want to add a master on a street car you can wire it anyway that you choose but if it is to act as a single switch to cut all power you need to also cut power from the alternator or the car will continue to run until a second switch, the ignition, is also opened.

[JohnK]

Agree with NAZ - it comes down to why you're adding a master switch and what you hope to accomplish with it. In my case, I added it for a few reasons, none of which have anything to do with complying with race sanctioning body requirements. If I'm being honest, I wanted the cool race car aesthetic of having a master disconnect switch. Secondly, it's a handy power wire consolidation/distribution point on the firewall. Lastly, it kills power to all non-essential (i.e., everything other than the coyote PDB) items. As far as killing the engine goes, it comes down to how you've wired the car. In my case, I wired the fuel pump power per the FFR coyote install instructions with the coyote green wire activating the fuel pump relay trigger but the RF harness is still providing fuel pump power. So I think that switching off the master disconnect will kill power to the fuel pump and stop the engine (haven't tried though).

Edit: upon further thought, I have the alternator output running into a bus bar that feeds into the RF harness, so the alternator may keep the fuel pump powered.

[GTBradley]

Right, keep forgetting the racing aspect. Personally, I prefer the cutoff switch to be a battery isolation system. I don’t want it to kill the engine since I can do that with the ignition switch. This way I can prevent discharge while the car is stored and use it to work on the electrical system too. The risk for using these switches is they can fail or someone can disable your car by taking the key, if it’s a removable type.

[DesertSn8ke]

First time post here, I have a Coupe kit coming sometime in October. I ordered the FFR electrical completion kit, so Ron Francis harness and other misc. parts. Just wondering about folks overall impression of the FFR supplied harness and parts. Worth it, or.... are there better options for similar $$?

[edwardb]

First time post here, I have a Coupe kit coming sometime in October. I ordered the FFR electrical completion kit, so Ron Francis harness and other misc. parts. Just wondering about folks overall impression of the FFR supplied harness and parts. Worth it, or.... are there better options for similar $$?

Welcome, and congratulations on your kit order. Your questions is slightly off topic. So probably best for the future to start a new thread. Best practice plus you'll get more responses. To answer your question though -- you'll get different opinions. I've done multiple builds with the Ron Francis harness and don't have any issues with it. Simply, it works. There have been several posts describing incorrect pins (e.g. inserted into the wrong cavity during assembly) and at least one I recall with a poor crimp. But as is often the case, the defects get posted so it's easy to maybe get a skewed opinion. I've not had any defects with mine as have hundreds (thousands?) of other builders. The only negative I would say about the harness is it's a universal harness for Factory Five. Same one used on the Roadster, Coupe, Hot Rod, etc. So the harness leg lengths may not be optimal for your Coupe. But that's the case anyway as usually not every installation is the same. You can leave it as is, which most do, or you can modify it. I've done a little of both. But a universal harness from XYZ company would have the same issue. It's not going to necessarily be optimal or perfect for your build and will require some level of adjustment. My recommendation? Stick with the Ron Francis. It works, and if you have issues, most of us on here have experience with it and can help as needed. Good luck with your Coupe build. We love ours.