2 big selonoids between batt and fuse panel????

[adamanderr]

i paid an electrician to com out to sort out my trailers and running lights but he couldn't work on them because there was no volt coming from my fuse box. apparently in the fuse box are between the battery and the fuse panel there are two approx. 2in diameter by 2in selenoids
with a bunch of components tied into them,
they don't look joined to each other,
they resemble small electric motors, think old vcr style.
with two bolt down terminals on the end.
(at least thats what he deduced them to be, i don't touch electronics just over my head rear end replacements)
can anyone tell me:
what they are
why do i need them

im going to rebuild the fuse panel as soon as i find out and feel i could eliminate them.
my fold out stop sign was air operated and there not washing fluid pumps.....
thanks

 

[the_experience03]

Did he try turning the key on before condemning the wiring? Those solenoids just allow you to kill power to multiply components with the key off. All those components tied to those are designed to only work with key power on. You can eliminate the solenoids no problem, but you're going to kill your batteries if you leave any accessory on. Car manufacturers do the same thing with Chrysler stuff having their Automatic Shutdown relay, Fords uses their Constant Control Relay Module, and GM...well...GM used their ignition switch itself to carry that current for a LONG time, but they now use a series of switched relays as well.

My recommendation would be to leave the solenoids as-is. Turn the key on to verify whether or not they are working. Also, I have a lot of buddies that are electricians whereas I am a mechanic. I can tell you they don't know a darn thing about DC voltage and how cars are wired. Of course I get lost when they start talking about the different phases of power in AC wiring. Hopefully your electrician is good with vehicle electrical.

 

[Redbear]

The solenoids allow the key or battery switch to turn high current loads on and off. They do burn out after time. If all the power on a skoolie went through the key switch, it would burn out much, much faster. The big threaded studs on the right and left are the input and output. They are supposed to be connected together inside when power is applied to the little studs on the front.

If there is no power to one of the big studs, it doesn't matter if the solenoid goes 'click' when the key is on. Look for a bad battery feed.

Next, see if the small front studs have power on when the key is on. If there is power across the small studs, and power to the big stud on one side, but no power to the other big stud, you can assume the solenoid is not passing power and is bad. If there is never power to the small studs, then look for problems in the key switch or wiring.

If you want to eliminate the solenoids, one solution would be a heavy-duty manual disconnect switch to cut all the power when you are not running the bus.

 

[lapeer20m]

The solenoids allow the key or battery switch to turn high current loads on and off. They do burn out after time. If all the power on a skoolie went through the key switch, it would burn out much, much faster. The big threaded studs on the right and left are the input and output. They are supposed to be connected together inside when power is applied to the little studs on the front.

If there is no power to one of the big studs, it doesn't matter if the solenoid goes 'click' when the key is on. Look for a bad battery feed.

Next, see if the small front studs have power on when the key is on. If there is power across the small studs, and power to the big stud on one side, but no power to the other big stud, you can assume the solenoid is not passing power and is bad. If there is never power to the small studs, then look for problems in the key switch or wiring.

If you want to eliminate the solenoids, one solution would be a heavy-duty manual disconnect switch to cut all the power when you are not running the bus.

excellent post!

one more thing is to not only make sure there is power to one of the little studs, but also a ground to the other little stud. Lots of wierd seemingly unexplainable problems in 12 volt electrical system ends up being a bad ground.

In my buses, i find the problem with leaving the key on is that it makes the backup brake elecric motor run, which obviously takes a lot of current. I like to find a seldom (never) used switch on the panel and wire it to turn on the solenoid that feeds power to the switch panel. This allows me to use my radio and other 12 volt accessories while parked with engine off, but still allows power to be completely shut off in the bus with just the flip of a switch.

 

[the_experience03]

one more thing is to not only make sure there is power to one of the little studs, but also a ground to the other little stud. Lots of wierd seemingly unexplainable problems in 12 volt electrical system ends up being a bad ground.

Assuming that little stud actually goes to ground. On most of the old Ford starter solenoids I've seen they actually ground through the mounting holes and that second little stud is just there to help you blow fuses when you ground it.

And I will agree with you 100% that grounds are vastly important, usually neglected, and will cause ALL kinds of crazy things to happen.

 

[Redbear]

I should have been clearer: If there are two studs, measuring from one stud to the other proves both hot and ground wiring. If there is only one stud, then measure to the mounting frame where the internal ground is connected.

The battery disconnect solenoids on many commercial motor homes have the hot, not the ground, connected all the time. There is a disconnect switch inside the entry door that grounds the solenoid to turn on the power. This saves the manufacturer from running two wires. Switching either hot or ground works on a two-terminal unit.

In most skoolies I expect a key-switched hot wire. The accessory solenoids were where I usually connected power when installing two-way radios. Alternately, if putting a low transmit power radio into an (older?) International, there is a an unused accessory spade on the back of the key switch in the one-o'clock position that I can find just by feel. But I digress.

I dislike solenoids for battery disconnects, if for no other reason than they use electricity to keep the electricity on. Not an issue for engine-run accessories when there is charging current, but very bad for boondocking. There are contactors available out there, with two sets of control studs. Momentary 12 volts from a pushbutton to one coil latches the power on, a pushbutton powering the other coil latches it back off. No power is used by the contactor once it latches.

Of course, the most common problem with the good old manual switch is forgetting when to turn it on or off!

 

[the_experience03]

There are contactors available out there, with two sets of control studs. Momentary 12 volts from a pushbutton to one coil latches the power on, a pushbutton powering the other coil latches it back off. No power is used by the contactor once it latches.

Now these I would like to find! I've used latching relays before, but they all drew power to keep them latched from the source (pin 30 if you will) even after the momentary input was disconnected. Of course a relay only requires about 300mA to latch so it really isn't a parasitic draw issue. But solenoids...well...I've seen them require up to 10 amps to latch!

 

[SHORTS]

their are lots of different solinoids, the old 4 stud ford solinoid is for short duration high amperage, the bracket is the ground, the 2 large terminals are a high amperage(starter) switch, one of the small terminals energizes the solinoid, the other small terminal is hot when the switch is energized, used to boost the ignition voltage while cranking, used on old points type ignition with a ballast resistor to keep the points from burning up while running. these solinoids are not designed for continous use. the newer ford style starter solinoids may have only 3 terminals, 2 large high amp starter switch, 1 to energize and bracket to ground.

their are power solinoids that are designed to be turned on for extended periods like to power high amperage devices, they look just like the starter solinoids but internally they are different.

grounding solinoids look identical to other solinoids but again are different internally and energize when they are grounded,

the point is you need to properly identify the solinoids properly and use the appropriate replacement part that visually may or may not look like the original part.

personally i prefer to use a Cole Hersee type manual battery switch, it's about 6 " in diameter and has off,batt 1,both, and batt 2 positions, they are relativly common in marine and rescue vehicle applications, again you need to look at the specs to make sure that you get a switch that will handle the amps you will subject it to.