Hi, here's my question; should I use a relay or solenoid to cut power to my charge line for my 7 way trailer connector when the key is turned off. I can get a 30 amp relay from Napa for $3.99, a solenoid is $27.99. I'm not trying to cheap out, but if the relay will do the smae thing, I'd rather have the extra money in my pocket.
The solenoid is a bit more robust and would allow much more current. Most trucks are capable (at least supposedly) of providing 40 amps so I've always used the solenoid.
Scott, Grace and Wesly
2003 Dodge 3500 4x4 Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
You need to make sure that $3.99 relay is designed for continuous duty if you use it in that application. Of course, the same could be said about the solenoid. lou
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Actually, a relay is a solenoid, or a solenoid is a relay. In common useage, the solenoid has a higher current capacity. You will want one rated for "continuous duty", no matter which you choose, and be sure the capacity is adequate.
CM1, USN (RET)
'94 Dodge 3500 4X2 CTD, Std. cab, LB, 5 speed, 4.10 LS diff., Jacobs Rambrake, 273,000 Miles
'99 Monaco McKenzie 32' triple slide
'95 Tioga 29H Ford-based Class C
Daily driver: '06 Jeep Liberty CRD
Towed: '06 Jeep Rubicon Unlimited
mowermech wrote: Actually, a relay is a solenoid, or a solenoid is a relay. In common useage, the solenoid has a higher current capacity. You will want one rated for "continuous duty", no matter which you choose, and be sure the capacity is adequate.
Right on and add
That a solenoid is an electro/mechanical device that uses electrical
power to move an armature.
A 'solenoid' in automotive terms usually refers to the starter solenoid,
which has to move lots of metal and some times against the gear teeth
that are not perfectly matched to mess. So it has to have enough force
to ram it in there....BUT....it's designed for short term use. The holding
current will be too large for the thermal rejection (heating it up
too much) of the design.
A relay uses a solenoid to move the armature, which has electrical
contacts. That either opens them or closes them on the electrical
circuit. Usually under 10 amps and if larger it's called a 'contactor'.
Though some consider 15, 20, 25, or more before it's called a contactor.
Their solenoids are designed to be energized all day (24/7) with
not heating problems.
Look for a 'relay' or 'contactor' of the correct size and voltage ratings.
Be sure to have the coil and contact circuits protected by either fuses
or circuit breakers.
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
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