USB outlet and heater on starter batteries. Please help!

[Flynt]

Originally Posted by Rwnielsen

When installed correctly and everything is off, your meter will read a ground through both of the small wires on the solenoid. That is just a coil winding. A decent meter will tell you ohms of resistance between the two but either way, those are not your tie in points. The two larger wires, one to the battery and the other to the fuseblock are what you're interested in.
In your picture there's a ground stud in the top left. That would be a great place for a ground from your heater. Personally, I'd ground it to the bus frame right where it's mounted as well.
Your power will then come from the large terminal that goes to the fuse block. Use a large, crimp type, ring terminal, under the large wire terminal. You should put your fuse in that general area as well.
Now...when you turn on the key you will have full voltage at your power feed wire and a redundant ground. That will work .

Okay so If I'm understanding everything correctly, both of the smaller ground terminals on the solenoid should go to the same place? Since one ground is making a poor connection, since its attached to the fuse block, would it be a bad idea to just connect those two terminals together and have one wire going to the main ground stud on my panel?

[rossvtaylor]

Originally Posted by Flynt

Okay so If I'm understanding everything correctly, both of the smaller ground terminals on the solenoid should go to the same place? Since one ground is making a poor connection, since its attached to the fuse block, would it be a bad idea to just connect those two terminals together and have one wire going to the main ground stud on my panel?

The smaller terminals on the solenoid are the coil (trigger) which provide power to the electromagnet inside the big switch, which connects the two large lugs together (allowing power to pass through those). One small terminal will be connected to a + and one will go to a ground. If you connect both to ground, the solenoid won't work...and you might blow a fuse if the positive + is still connected, too. They are not directional, so it doesn't matter which small terminal is + and which is ground...but they can't both be ground or +.

[Rwnielsen]

Large wire on the load side is your connection point for switched power

[cadillackid]

ross, it sounds to me like they are backfeeding through the coil on the solenoid...



so its a good chance that the ignition switch grounds the ground lead on the solenoid when turned on... the Positive 12 will be to the one small lead all the time.. if you measure from the other small elad on the solenoid to a real ground while the ignition is off.. you will have voltage as that lead floats in the absence of circuit ground...


if the heater positive were connected to the side which gets grounded by the ignition switch.. then it would get speudo voltahge through the coil... once the heater kicked into "full start" it would probably actually trip the coil in the solenoid to fire, turning all the accesories in the bus on and dropping system voltage to the point the heater shuts down and the process starts again.. solenoid disengages.. turning on the ingition would completely ground out the heater and it would be InOp

[rossvtaylor]

Originally Posted by cadillackid

ross, it sounds to me like they are backfeeding through the coil on the solenoid...



so its a good chance that the ignition switch grounds the ground lead on the solenoid when turned on... the Positive 12 will be to the one small lead all the time.. if you measure from the other small elad on the solenoid to a real ground while the ignition is off.. you will have voltage as that lead floats in the absence of circuit ground...


if the heater positive were connected to the side which gets grounded by the ignition switch.. then it would get speudo voltahge through the coil... once the heater kicked into "full start" it would probably actually trip the coil in the solenoid to fire, turning all the accesories in the bus on and dropping system voltage to the point the heater shuts down and the process starts again.. solenoid disengages.. turning on the ingition would completely ground out the heater and it would be InOp

Absolutely possible, too. So many ways to mess that up! All of these possibilities would be fixed if they use a large-diameter ring terminal and a fused line, connected to the large terminal which has power when the want...so, either the one that's hot all the time or the one that's hot when the solenoid is switched on. I think trying to connect their heater to the small terminals is complicating things, whichever side they're using. Your thoughts are good, as usual sir.

[Rwnielsen]

Originally Posted by cadillackid

ross, it sounds to me like they are backfeeding through the coil on the solenoid...



so its a good chance that the ignition switch grounds the ground lead on the solenoid when turned on... the Positive 12 will be to the one small lead all the time.. if you measure from the other small elad on the solenoid to a real ground while the ignition is off.. you will have voltage as that lead floats in the absence of circuit ground...


if the heater positive were connected to the side which gets grounded by the ignition switch.. then it would get speudo voltahge through the coil... once the heater kicked into "full start" it would probably actually trip the coil in the solenoid to fire, turning all the accesories in the bus on and dropping system voltage to the point the heater shuts down and the process starts again.. solenoid disengages.. turning on the ingition would completely ground out the heater and it would be InOp

That's an interesting point but, typically, the signal to the solenoid is positive. The reason some solenoids have two control connections is so they can be mounted on an ungrounded surface and grounded elsewhere with a wire. On a contactor or relay they would be labeled A1 & A2 (A for armature). Any one of us could have had poor Flint up and running in minutes if we were nearby.

[rossvtaylor]

Originally Posted by Rwnielsen

Any one of us could have had poor Flint up and running in minutes if we were nearby.

And any of us nearby would, too. That's what I love about this group.

[Flynt]

Originally Posted by Rwnielsen

Attachment 71079

Large wire on the load side is your connection point for switched power

Right so I believe that's part of my problem. The ignition switch terminal on the solenoid just has a wire going to one of the grounding points on my panel. That's how it was setup when I got it. Is there supposed to be a wire coming from the dashboard somewhere for that?

[Rwnielsen]

Don't mess with any of the previous connections. The 2 small wires ...one comes from your ignition the other is ground. The larger wires are battery and load. With the key off one side will be hot and the other (your target) will be off. When you turn on the ignition the solenoid closes with an audible clunk and it powers the fuse block. You want to connect to the load side so the heater will not have power when the bus is not running.

In practice this may not be the best way to hook it up as the heaters need to go through their shut down cycle and if you forget and just turn off the bus it could cause damage.