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Rear end of truck is wired and now headed north to the front end with the power users... making a list of relays and checking it twice... I'm thinking...
high beams
low beams
radiator fan
tilt hood
air conditioner
windshield wipers...
horn
what else am I missing from the cab forward ?
and at what amp pull would you add a relay ? 5?? 10 ?? etc
even though my trans cooler fan isn't high amp (4.8)... I'm considering one there
From a technical standpoint there would be no advantage in using a relay where the load current is equal to or less than the coil pull-in current.
That said, manual switch contacts are quite robust and a good quality snap switch should handle 15 amps easily. However, a relay allows you to control a large amperage circuit remotely with a tiny switch.
I use relays in all circuits over five amps., even my battery isolation relay is controlled by a 5 psig close-on-rise oil pressure switch.
Last edited by Mixer man; 04-13-2018 at 09:12 PM.
Reason: Oops.
John,
Given the level that you are building your truck to, is your truck more likely to ride in a trailer than pull a trailer!
Last year I stopped at a toll booth towing with Willard and got asked that question.
initial plans were to build a Coke box trailer for 'incidentals" but after talking to a few folks, decided against it... due to sway, short length, etc... sold the coke box,. I had already installed the trailer hitch so it's there if it's needed behind a drop down tag.
I also have a trailer for the truck to ride on for long trips where the truck 'just has to go' Like Crusin the Coast in Biloxi... that's about 300+ miles and probably need two cars when we get there... so I've got both ends covered... BTW Love that trailer you're towing. Never seen one like it..., what are you hiding in there ???
Relays are best used on inductive loads rather than purely resistive ones. As Bob noted a quality manual switch can easily interrupt 15 resistive amps.
A little electrical theoey may clarify things so please bear with me while i get technical. Inductive loads 'kick back' a potentially high, and reverse voltage spike the instant the current flow is interrupted. Switches are designed to interrupt loads with little to no induced voltage spike. They 'snap' to aid in quickly and cleanly breaking the circuit. But inductive loads can produce voltage spikes that can cause an arc to jump between the open contacts, causing pitting or worse. In extreme conditions the load itself can be damaged.
Relays use various methods to quench arcing from the voltage spike. In short they are designed for inductive loads. Typical inductive loads in our trucks include motors, electric fans, horns, fuel pumps and even the relay itself (but they are small loads so work fine with a switch).
Sorry for the didactic rant, but hopefully this will help someone with the next wiring project.
initial plans were to build a Coke box trailer for 'incidentals" but after talking to a few folks, decided against it... due to sway, short length, etc... sold the coke box,. I had already installed the trailer hitch so it's there if it's needed behind a drop down tag.
I also have a trailer for the truck to ride on for long trips where the truck 'just has to go' Like Crusin the Coast in Biloxi... that's about 300+ miles and probably need two cars when we get there... so I've got both ends covered... BTW Love that trailer you're towing. Never seen one like it..., what are you hiding in there ???
j
John,
I tour with the early cars/Horseless Carriages, HCCA. I was loaded up in the picture to go to a 5 day HCCA tour that I set up in Downeast Maine, about 160 miles from home. See picture below loading up my 1907 2 cylinder Buick. I drove the Buick about 400 miles on that tour.
Answer to original question: as close to the device as possible. You'll only need to route power and signal to each relay, the remaining connections can be made at the device. Select a spot that is weather resistant and, if you're in the salt belt, protected from road splash/fog. A bank of relays can draw power from a single, adequately-sized and protected supply wire.
You can supply power to #30 and one side of the coil from the same power and switch the ground side of the coil. That way, should the switch leg short to ground, the only issue will be the device will be switched on and not a mess of wires melting your truck into the ground. If you are attempting to stay as close as possible to OE (my personal M.O.) just tuck them out of sight. Not everything requires a relay. For the purposes of this particular age group (vehicles, that is ;-) ) my thoughts are headlights, radiator fan(s), electric fuel pump(s), a/c compressor and bun warmers should be on relays. However, the largest OE draws of our trucks are the starter relay, headlights, heater fan and wiper motor (electric wipers, of course. ;-) ) But have you ever seen someone wire a separate relay for each fan or wiper speed? While the switches we get from the other side of the world, these days, are better than nothing they are only one step better than nothing. Mechanical switches go through some aggravation that relays don't (user abuse, primarily) so some weight has to be given there. My point is a couple extra relays can't hurt but there's also no reason to go crazy. Tip: I can pull a hundred relays in five minutes at a junkyard, throw the dude a fin and everyone's happy. Try that at A**** (it who must not be named.) Don't go spending $3 - $15 for a relay or circuit breakers, etc. Same thing with wiring. If it floats your boat, Woohoo!, go for the cotton braided stuff. However, I just googled "When was the last time a pickup truck won an award at Pebble Beach?", I'm sure you're picking up on where I'm going, especially after considering 85+% of the wiring in our trucks is well out of sight...
I've mentioned this before - if you want to learn automotive electrics there is a great site, built by a Toyota trainer (ex?). Don't be dismayed because it begins at the electron level, it rapidly moves past that (I'm factory trained by Ford, GM, Saab and Isuzu and I'm here to tell you they all start in the same place.) By the time you finish the modules you'll understand automotive electrics from day one to what you'll be driving ten years from now. Click here: Automotive Training and Resource Site Did I mention it's FREE?
Bill !!!! that is a beauty. Is that a custom built trailer ??? never seen a soft sided one like that... wonder how it travels and holds up... love to see some interior and build shots of the trailer.
j
Answer to original question: as close to the device as possible. You'll only need to route power and signal to each relay, the remaining connections can be made at the device. Select a spot that is weather resistant and, if you're in the salt belt, protected from road splash/fog. A bank of relays can draw power from a single, adequately-sized and protected supply wire.
You can supply power to #30 and one side of the coil from the same power and switch the ground side of the coil. That way, should the switch leg short to ground, the only issue will be the device will be switched on and not a mess of wires melting your truck into the ground. If you are attempting to stay as close as possible to OE (my personal M.O.) just tuck them out of sight. Not everything requires a relay. For the purposes of this particular age group (vehicles, that is ;-) ) my thoughts are headlights, radiator fan(s), electric fuel pump(s), a/c compressor and bun warmers should be on relays. However, the largest OE draws of our trucks are the starter relay, headlights, heater fan and wiper motor (electric wipers, of course. ;-) ) But have you ever seen someone wire a separate relay for each fan or wiper speed? While the switches we get from the other side of the world, these days, are better than nothing they are only one step better than nothing. Mechanical switches go through some aggravation that relays don't (user abuse, primarily) so some weight has to be given there. My point is a couple extra relays can't hurt but there's also no reason to go crazy. Tip: I can pull a hundred relays in five minutes at a junkyard, throw the dude a fin and everyone's happy. Try that at A**** (it who must not be named.) Don't go spending $3 - $15 for a relay or circuit breakers, etc. Same thing with wiring. If it floats your boat, Woohoo!, go for the cotton braided stuff. However, I just googled "When was the last time a pickup truck won an award at Pebble Beach?", I'm sure you're picking up on where I'm going, especially after considering 85+% of the wiring in our trucks is well out of sight...
I've mentioned this before - if you want to learn automotive electrics there is a great site, built by a Toyota trainer (ex?). Don't be dismayed because it begins at the electron level, it rapidly moves past that (I'm factory trained by Ford, GM, Saab and Isuzu and I'm here to tell you they all start in the same place.) By the time you finish the modules you'll understand automotive electrics from day one to what you'll be driving ten years from now. Click here: Automotive Training and Resource Site Did I mention it's FREE?
We are of like mind Beav... easier to put one and not need it than to wish you had a fire extinguisher !!. I picked up a pack of Boschs off Amazon 5 for 15. waterproof and heavy duty wiring. I'll post pics later..
A little electrical theoey may clarify things so please bear with me while i get technical. Inductive loads 'kick back' a potentially high, and reverse voltage spike the instant the current flow is interrupted. Switches are designed to interrupt loads with little to no induced voltage spike. They 'snap' to aid in quickly and cleanly breaking the circuit. But inductive loads can produce voltage spikes that can cause an arc to jump between the open contacts, causing pitting or worse. In extreme conditions the load itself can be damaged.
Relays use various methods to quench arcing from the voltage spike. In short they are designed for inductive loads. Typical inductive loads in our trucks include motors, electric fans, horns, fuel pumps and even the relay itself.
I’m also a believer in using relays in any application where there is a substantial inductive load. I also prefer to install a diode across these loads to dissipate the above-mentioned spike and help the relay contacts last as long as possible. Ford did that for years on their A/C clutches. Google “flyback diode” for more information. They’re cheap and usually easy to install.
04-13-2018, 05:28 PM
Like Crusin the Coast in Biloxi... that's about 300+ miles and probably need two cars when we get there... so I've got both ends covered... BTW Love that trailer you're towing. Never seen one like it..., what are you hiding in there ???
. I picked up a pack of Boschs off Amazon 5 for 15. waterproof and heavy duty wiring. I'll post pics later..
