So I am going to assume my isolator is broken (judging by how old it is) and NOT that it was wired wrong. Although it does seem to be wired differently than the instructions I see for new ones. For example... the alternator goes to the isolator, but the isolator does NOT go to the engine battery. It is as if the alternator itself splits the charge to the engine battery and THEN also to the isolator. Picture of My isolatorLike A,E,F are all linked together. E comes FROM my alternator and then A just loops up to the isolator (to give it power). C must be wired to my ignition to turn it on and off and I assume the BLACK wire D goes to charge my house battery (It vanishes into the firewall). Although there would then me NO "Negative" running from the isolator to the house battery. NO LINE goes from the isolator to my engine battery, that battery is connected directly to the alternator.line F is a mystery... (It is red) and it travels to some kind of thing pictured HERE that seems to be attached to my air conditioning (That is not working AND not even connected anymore)... Not sure if that is relevant. So TWO questions... 1. How many AMPS do I need the new isolater to be? I saw one on Amazon that was 80 amp and I imagine the one I have is that small at least.2. Any advice on how to connect the new one? I will just kind of copy the way it is hooked up now (even though it is slightly different than the directions say)

I would go to a relay rather than a diode. I replaced mine with units rated at 200 amps.

Is it possible for the OP to drop down several topics and review my response including photos and link to a smart solenoid? i just lost my appetite looking at that image of the OP's. There is no reason to endure such a improvised disaster in waiting.

pianotuna wrote:I would go to a relay rather than a diode. I replaced mine with units rated at 200 amps.X2. I would never go back to diodes.Much more reliable and no voltage drop.

What the OP has is a relay- A is a common hot lug, that's hooked to the relay through a circuit breaker, which is mounted to the control post of the relay- used to be common, kind of wonky to me. C is the control lead from a switched ignition lead. The engine battery must be hooked to the alternator elsewhere.

Only armageddon prevention protection should be placed in between an alternator and the chassis battery. The safest protection as far as reliability is concerned is a fusible link. Fuses can corrode, breakers can break, and switches are controlled by mistake makers.In my designs I am so touchy about this that I insist on a straight run from alternator output stud direct to battery positive. A 2nd cable from battery positive gets distributed after a very short run. The manifold at that point gets branch over current protection devices.Why people gnaw fingernails to the quick over the supposedly "exposed therefore vulnerable" alternator to chassis battery wire is beyond me. The circuit is protected by a fusible link. Want tough high temperature wire? Use XL cross linked polyolefin insulated wire. Insulation is extra hard and extreme temperature resistant. Black nylon spiral wrap can be applied over the cross link wire. Then, it would take pressing directly against an exhaust manifold or hammer and chisel to compromise its integrity.Ill furnish a link below in another response to a relay that shames the reliability of a metal an relay if an individual insists on using a control wire or switch.

Help replacing an OLD isolator | Good Sam Community

MrWizard
Moderator
Jul 27, 2017
IDK
but if the a/c does not work
maybe the previous owner AKA the 'PO' wired it do turn on, using the a/c switch on the dash

try that and see if it comes on and starts charging your battery
tommymsw
Explorer
Jul 27, 2017
MrWizard wrote:
sorry there is NO such thing as an air conditioning charger

you may have read some where

about somebody using a 120vac BATTERY charger

many of us carry a battery charger
it serves as a backup, a way to help a neighbor start his car
sometimes an extra boost to what the 'built in' converter is doing

your RV has or should have a 'converter' aka built in battery charger that works automatically when plugged into shore power

Any idea why my isolator is connected FROM the Air Conditioning unit? As well as the alternator?
MrWizard
Moderator
Jul 26, 2017
sorry there is NO such thing as an air conditioning charger

you may have read some where

about somebody using a 120vac BATTERY charger

many of us carry a battery charger
it serves as a backup, a way to help a neighbor start his car
sometimes an extra boost to what the 'built in' converter is doing

your RV has or should have a 'converter' aka built in battery charger that works automatically when plugged into shore power
tommymsw
Explorer
Jul 26, 2017
Sorry... to the other responder... AC was AIR CONDITIONING. One of the RED wires comes from the AIR CONDITIONING system. I read that the isolators can be charged from alternator, solar, or air conditioning chargers.

Mine appears like it was hooked up to both? Or perhaps to the air conditioning unit and then to the alternator when the air was taken out or broke.

that may also explain why the isolator is connected DIRECTLY to the alternator and NOT through the chassis battery.

I will just replace it with what was there and worry about the rest later. Who knows... maybe replacing will not fix the problem and my problem was in wiring... Although it looks like the wires have been where they are for YEARS.
MEXICOWANDERER
Explorer
Jul 26, 2017
I replaced many before my boat repair business was murdered.

Isn't that the truth...

Matt, I have been following your replies for years on this forum. May I state that the boating industry lost a good tech when you were forced to leave.
Matt_Colie
Explorer II
Jul 26, 2017
What OP has is not an Isolator.
It is a combiner and they are great right up until they go bad. They can be hard to trouble shoot without the main engine running. It can be done. The biggest problem was owner's repairs when they put in a starter contactor and not one rated for continues duty and it burned up every time that they replaced it. They called me for the third or forth. I kept them in stock.

I replaced many before my boat repair business was murdered.

Isolators take more engineering to install and make work few builders want to go to that effort of doing. Some chassis makes don't allow it because of warranty. The isolator in my coach is a designed in double diode. It is 44 years and 170Kmile old like the rest of the coach.

Matt
j-d
Explorer II
Jul 26, 2017
I looked at Mex's linked relay on Amazon and when I did, noticed there are Three- and Four-Wire versions of these relays.

The one in OP's pic, and the one Chris linked, are Three-wire. Two big lugs for the current that's being switched by the relay, and then one small lug to energize the relay. In this case, from the RUN terminal of the Ignition Switch, or whatever it's linked to. The Relay's CASE must be Grounded to the Vehicle to work. With a Four-Wire, the second small lug goes to Ground also. Could be right to a mounting fastener for the Relay, or off to somewhere else on the vehicle.
MrWizard
Moderator
Jul 26, 2017
use a cheap small relay have the contacts stick ! (chassis battery will drain with camper use)

use to small of a diode based isolator and have a diode burn out ! ( battery circuit with bad diode will not charge)
MrWizard
Moderator
Jul 26, 2017
tommymsw wrote:
ALSO...

The "extra" red cable to the isolator seems to come from my AC Relay... Why? Was this because it was getting charge power from my AC r AND my alternator? Or to allow the charge from my alternator to go to my AC?

The AC is no longer functioning and disconnected... So I assume I can just tape this wire off and ignore it on the new isolator.

do you mean A/C air-conditioning
or AC like in 120vac

"was getting charge power from my AC" .. what the heck does this mean ?

charge power from your air-conditioning ?
MEXICOWANDERER
Explorer
Jul 26, 2017
Yup. I always assume the use is for real. Jumper wires, plumber's tape, and coat hangers allow fun usage without needing to concern ones self with isolators or relays or most everything graded above "basic". I have met innumerable people down here that use a six-inch jumper clip across a failed solenoid and the thought of doing things any other way brings a smile.

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