HELP!! Wire size recommendations for 4120 cab power circuit

[jenkinsph]

Well most of the responses I have made are based on my experiences as a licensed electrician and retired broadcast engineer. That combined with my boat wiring experiences combatting corrosion and vibration helped to form my thoughts on all of this.

In the beginning your problem seemed to be crimping 8 ga. terminals, I would think one of your friends would have a crimping tool to accomodate this. As I am sure you are aware if you purchase a simple fuse block rated for 40 amps that it will have a screw terminal to accept a ring terminal. So I still can't see the barrier that exists that would eliminate using an 8 ga. wire.

As far as fusing at the battery end it is considered a good practice to place the fuse within seven inches of the battery terminal. I also mentioned the tinned wire because it has less corrosion issues, I like to do it once and do it right.

At any rate you have my apologies for dragging this out as none of this is more complicated than a bell circuit, everyone knows what is needed and it is your tractor. I have been bored to death lately having to be a care giver and haven't been able to get away from the house enough.

Got to ask this though why didn't you get a cab tractor to start with? I thought several of us encouraged you to.

 

[arrabil]

The only 8ga on a vehicle will be from the battery to the starter and it will carry 200+ amps. There is completely no need for that in anything here. Otherwise your vehicles would have 8ga so the manufacturer wouldn't get sued. The biggest wire in your vehicle goes to the seat heaters and power windows and its never bigger than 12ga because they use up to 40A max.

Neither is there any need for tinned wire because this isn't a corrosive marine environment.

Just go to Advance Auto or WalMart even and look at what they sell for automotive DC use. Its not special because it isn't a special environment.

However, I would wire one fuse for the whole power wire near the battery and then use the other fuses to protect the individual circuits from overloading one another. [Edit: Post #37 says he already plans on doing this.] And while I've heard the adage about fuses being near the battery, every vehicle I've ever owned exceeded the 7". Heck, BMWs put the battery in the trunk and the fuses in the front. And the 4200 exceeds the 7" by 2+ feet.

 

[jenkinsph]

If you want to use WalMart as an example of wiring accessories

I rest my case.

 

[arrabil]

You're kidding, right?

 

[mjncad]

I buy my automotive electrical parts from Del-City. Del City - Wiring Products and Professional Electrical Supplies

Thanks for posting the wire chart Arrabil.

 

[OtterBrookStables]

The isolation part of a relay is more practical than plain isolation. You don't want 40A of current flowing through the same switch where your finger is. So you use a relay to direct the current to the load while maintaining in-cab safety. My guess is this came about from early car fires more than any other reason.

EDIT: With that in mind, I would not run 18A of lights through one switch without a relay. You'll notice that the best switch you can buy at NAPA will be 12V/15A so... [and most likely you'll only find 12V/10A]

Re: isolation - your point is correct, but the confusion in this thread is that using a control signal to switch in all 40A to the bank of switches being incorrectly considered isolation.

Re: lights: There will be a switch for the front lights and a separate switch for the rear lights - 9A each.

 

[OtterBrookStables]

Well most of the responses I have made are based on my experiences as a licensed electrician and retired broadcast engineer. That combined with my boat wiring experiences combatting corrosion and vibration helped to form my thoughts on all of this.

In the beginning your problem seemed to be crimping 8 ga. terminals, I would think one of your friends would have a crimping tool to accomodate this. As I am sure you are aware if you purchase a simple fuse block rated for 40 amps that it will have a screw terminal to accept a ring terminal. So I still can't see the barrier that exists that would eliminate using an 8 ga. wire.

As far as fusing at the battery end it is considered a good practice to place the fuse within seven inches of the battery terminal. I also mentioned the tinned wire because it has less corrosion issues, I like to do it once and do it right.

At any rate you have my apologies for dragging this out as none of this is more complicated than a bell circuit, everyone knows what is needed and it is your tractor. I have been bored to death lately having to be a care giver and haven't been able to get away from the house enough.

Got to ask this though why didn't you get a cab tractor to start with? I thought several of us encouraged you to.

First - no aplogies necessary - we're all just trying to help each other out. So please - keep the thoughts coming.

The 8AWG issue was not a crimping tool, it was a terminal availability issue. I could not find a spade terminal to fit 8AWG. And - good suggestion - I will be using a fuse block to distribute individual circuits to the switches.

Re: the cab - good question! I have a good answer. First - the 4120 is not offered with a cab. I got a really good deal on the 4120 and will have less than $2K into my cab addition (got a GREAT deal on the cab!). Moving up to a 4320 cab would have been about $8K. Also - many don't realize how close in performance the 4X20 tractors are. My dealer's chief mechanic told me the 4120 is by far the best bang for the buck. all of the 4X20's have the same exact motor. The only difference is in fuel and air delivery. Further - he knows for a fact (from dyno results) that JD is conservative with their HP ratings. My mechanic claims the 4120 on a dyno is actually closer to 50HP. They under-rate the various 4X20 models to make the published HP gap between models greater. They do this in an attempt to justify the cost deltas. For my purposes, the 4120 is more tractor than I will ever need (bold statement huh!).

 

[OtterBrookStables]

Got the install complete - everything installed and wired up. Murphy's law is in full effect, however! Everything I installed and wired - the rear wiper, front work lights, rear work lights, fan, dome light, and strobe - all work perfectly - BUT the one item delivered installed from the factory - the front wiper - doesn't work!!!

The circuit blows the fuse when I flip the switch on (not before the switch is turned on). Double-checked all wiring to the wiper and tried again -same thing. The wiper motor must have a short in it. I'll be calling the dealer tomorrow to get a new one sent out ASAP. What a dissapointment after all that work!

At least the rest of the stuff works properly. I promise to post some pics asap. This turned out to be one nicely set up 4120. The entire cab package with all of those options cost me less than two grand - pretty darn good in my book! The 74" Frontier blower is UNSTOPPABLE! I can run that thing right through a huge snowbank and the tractor never even misses a beat.

 

[arrabil]

I would try a 20 amp bigger fuse on the motor and see what happens. If it doesn't pop, you'll know the circuit is too small. And if it does pop you'll reconfirm what you've found. Actually, I would just wire the motor direct to the battery temporarily and see if it spins.

The only reason I suggest it is because electrical motors are nearly unstoppable nowadays and even the chinese ones have a low failure rate.

 

[OtterBrookStables]

I would try a 20 amp bigger fuse on the motor and see what happens. If it doesn't pop, you'll know the circuit is too small. And if it does pop you'll reconfirm what you've found. Actually, I would just wire the motor direct to the battery temporarily and see if it spins.

The only reason I suggest it is because electrical motors are nearly unstoppable nowadays and even the chinese ones have a low failure rate.

Good suggestions, but no dice. You are correct though, motor failure is rare - but it does happen. On the second attempt, I did put in a 15A fuse, which still blew. The wiper came with a 7.5A fuse installed, just like the rear wiper I put in. This is the proper protection level for the motor - if it draws more, there is definitely an issue. Most likely a siezed rotor is the culprit - the cab was sitting in it's crate for a quite a while before I bought it. At any rate, I'm nearly positive the motor is junk. Thanks for the comments - keep 'em coming. Can't wait to get a few pics posted, but won't be until the weekend.