NEED HELP TO ID ELECTRICAL RELAY

vanamaniac · 12-28-2013, 11:15 PM

Hello group! Im relatively new to this forum and to RVS also.
Im excited to find this forum and all the info it offers!

We recently purchased a 1989 FORD E-250 FIESTA mini motor home /RV (basically like the better known high top Falcon models extended van body)

I had to replace the 3 -pole battery isolater box because the poles and connections were badly rusted and the secondary battery was not charging.
The wire that comes off the isolater for the secondary battery went to a small 2 ( threaded with nuts) pole relay switch (silver box with a base mounting plate and about 1.5" long x 1" wide x 1" thick) and the other pole wire goes to the the secondary battery (I assume as the secondary battery is in the rear of the van)

The poles on this relay switch were so badly rusted that even after 3 weeks of spraying them with WD40, one of the threaded poles still broke off when I tried to remove the nut..so I just cut the wire connectors so I could remove it and splice the two wires together with a butt connector until I can replace the relay.

There is a black stamping on the ends of the relay, but I cant make out the number even with a magnifying glass.

Does anybody know what this relay does ? Does it regulate the voltage to the secondary battery OR?

Do I HAVE to have one ? (I joined the two wires /bypassing the relay switch after removing it.

Anybody have any idea what value or number this relay may have so I can find a replacement?

Pre Thanks for any and all help on this issue.

Im trying to cover all the bases before we take this RV on the road and are anxious to get going!

Regards

TD

markopolo · 12-29-2013, 12:07 AM

Welcome to the forum vanamaniac

Often you'll see a thermal self-resetting type circuit breaker in the place you decribe. Like these: http://www.cooperindustries.com/cont...itbreaker.html

That's my guess. And yes, it's a good idea to replace it as it's there to protect the wire from overload. I'd size it (amp rating) based on the wire size.

g1g · 12-29-2013, 12:53 AM

I am not familiar with many different individual parts but my guess is a circuit breaker like Marco said. It looks like it mounts on the fender well or something like that and the cables connect to the poles.

vanamaniac · 12-29-2013, 02:13 AM

Thanks for the quick replies...Yes it does mount on the fender well right behind the battery isolator ..I was wondering if it may also be a small voltage regulator to the secondary battery?

I found a similar looking 2 terminal /wired voltage regulator on ebay
http://www.ebay.com/itm/Univerasal-12-V ... 6016.l4276

however the wires in my RV van are much heavier gauge than the ones on this regulator ..

any thoughts?

I'll check outthe link on those circuit breakers Marco !

Thanks for all the help!

TD

booster · 12-29-2013, 03:23 AM

I would also vote for a circuit breaker. The wiring from the engine to the batteries, after the isolator or separator, would usually have a breaker like that on each end of the wire. The ones currently used by many manufacturers are made by Cole Hersee.

slipbobber · 12-29-2013, 03:36 AM

Yes, it is a 12 volt breaker. From the pic it looks like it is 10g wire so a 30 amp should be good. Most any good auto parts store will have them. Just bring the old one in with the wire connector and they should be able to figure the rating.

vanamaniac · 12-29-2013, 06:53 PM

Thanks for all the good info guys..I went to my auto parts store and they were right on the rack in electrical..I have never replaced one so never noticed them..the manager suggested a 40 amp breaker to "play it safe" so that what I got.
Again..appreciate all your help as I was clueless never having to deal with this part before.

as a last question..what exactly does this breaker do? since its going in between the battery isolater and battery..does it keep the secondary battery from getting to much voltage during charging or what?

WJones · 12-29-2013, 07:20 PM

Imagine a short circuit between your wire and the chassis ground somewhere along the route of the wire going to the battery. Sparks would fly ... and who knows what would happen to the isolator and alternator trying to supply all that current. The breaker will cut off the supply as soon as the current exceeds 40 Amps.

booster · 12-29-2013, 07:27 PM

Quote:

Originally Posted by vanamaniac

Thanks for all the good info guys..I went to my auto parts store and they were right on the rack in electrical..I have never replaced one so never noticed them..the manager suggested a 40 amp breaker to "play it safe" so that what I got.
Again..appreciate all your help as I was clueless never having to deal with this part before.

as a last question..what exactly does this breaker do? since its going in between the battery isolater and battery..does it keep the secondary battery from getting to much voltage during charging or what?

The wiring from the isolator or separator to the batteries is one of the few places where you need to have it fused on both ends. Normally, breakers are on the feed end and disconnect if anything downstream shorts out and/or pulls too much current for the wiring. The wiring in this case has a feed on each end. Current will flow from the isolator to the batteries, but that wire also goes hot from the batteries and charger when the engine isn't running. For that reason you also need to have a breaker at the battery end of the wire. You may want to make sure you have one on the battery end, and that it is of the right amperage.

vanamaniac · 12-30-2013, 03:41 AM

OK..that helps...so if the current isn't cut off until it reaches 40 amps (with the breaker I bought)..should I reconsider and buy a 25 or 30 watt breaker so it shuts off the current to the secondary battery even sooner? wouldn't a 25 amp breaker make it easer on the alternator cause it would not be charging the secondary battery as much if the 25 amp breaker shuts current flow down sooner(than a 40 amp)?

booster · 12-30-2013, 04:11 AM

Quote:

Originally Posted by vanamaniac

OK..that helps...so if the current isn't cut off until it reaches 40 amps (with the breaker I bought)..should I reconsider and buy a 25 or 30 watt breaker so it shuts off the current to the secondary battery even sooner? wouldn't a 25 amp breaker make it easer on the alternator cause it would not be charging the secondary battery as much if the 25 amp breaker shuts current flow down sooner(than a 40 amp)?

The breaker is there to protect the wiring, primarily, against shorts that would overheat it and possibly start a fire. The breakers should be sized to match the capacity of the wiring, so you need to know the wire size to chose the proper breaker. The breaker size will have no real affect on how things work unless it is so small it trips all the time, when trying to charge the batteries. Our Roadtrek has a #4 wire to the rear with an 80 amp breaker. Older ones used a #6 wire with a 50 amp breaker, IIRC. If you can get to a section of the wire, you should be able to clean it off and it will say the gauge size on it.

Don't worry about the amperage to your batteries, unless the alternator goes bad and puts out way too much voltage, they will take only what they can handle. Get the biggest breaker your wiring can handle.

vanamaniac · 12-30-2013, 03:17 PM

Thanks again booster..It helps to understand how these things work and effect other parts of the system. I will follow your advice and see if I can get a gauge # on the wiring (it is covered up in the harness or I would already know)
Appreciate the info and advice!
Have a great New Year !

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