Boost relay problem

[Monaco_hwy]

I measured the voltages at the switch.
Switch not pressed: 13.52v, 0v
Switch pressed: 0.93v, 0.72v

The switch drops 0.2 volts. The 12 volt wire drops about 0.92 volts. The ground connection to the switch rises about 0.72 volts.

The wire at the relay is orange. The wire at the switch is also orange, but is much thinner. The schematic describes the wire like this, "12GA ORG TO BATTERY BOOST SWITCH". I assume that the "12GA" means 12 gauge wire. If that is true, then the wire at the switch is a long way from 12 gauge. It looks to be the same diameter wire that connects the instrument panel lights. The wire at the relay could be 12 gauge, but I could not find any printing on the few inches that I could see, but I don't think that it is 12 gauge either.

[YC1]

Run a temporary ground wire to the switch. It won't take much. I wrap a metal dental probe in tape all but the last 1/2 inch on each end.

An alligator clip on the end and the sharp probe to insert into places like the switch wires.

"Switch pressed: 0.93v, 0.72v" I believe your are losing about 1 volt give or take from the switch to ground. The switch itself should not drop any but age and lack of exercise could cause a tiny drop. The test clip/probe will eliminate the switch and wiring.

If the solenoid closes when you put your own ground on the wire at the switch, put the ground on each of the wires on the switch with it pressed to see if the solenoid closes. If it does, the switch is probably ok but I would replace it anyway, or take it apart and clean but things can go sproing doing that so you need a nice flat place with a towell and hold things close to the towell. There may be tiny springs in corners of the switch that are used for making the back light work.

By supstituting your ground this way you should be able to get things to come alive. The ground wire for the switch probably goes through a "Molex" connecter. The pins often need exercise by plugging and unplugging them.

If you can follow the ground wire for the switch you may find it connected to several other wires and that locations may need service/cleaning.

[Monaco_hwy]

It is real tight in there, behind the dashboard. I used probes that have sharp points to pierce the insulation to take my readings. It seems that everything contributes to the problem; switch, ground, and the long wire (and connectors) to the rear. I think that putting a Bosch relay in the high current box will solve the problem without ripping everything apart.

[YC1]

I understand your issue. But you really need to chase the ground wire down at least to make sure there are not other wires that may one day have issues as well.

Ground issues in and around dashes cause headaches so often it is just amazing.

If your grounding gets worse, the bosh relay will not function either.
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As a refresh of the battery combining/charging/ boost function, take a look at this device. https://www.amazon.com/Cole-Hersee-4...0LMGPHW2&psc=1It has a built in bi-directional circuit that would replace the Lambert and it has a boost function as well. The boost function needs either an ignition controlled voltage or you would have to cut the ground wire side of your switch and connect that to a known good voltage source.

Or you could simply install a manual switch next to the device to turn on the boost feature when needed. However, when you have the alternator running (good output), good solar output, or good shoreline/converter supply then the boost switch is not needed. The device will already be engaged.

This solenoid could go in place of your existing boost solenoid. Would be a very easy swap out.

[Monaco_hwy]

I am intrigued by the Cole Hersee 48530 that you mentioned. The manual for the device shows it wired to charge the house batteries when the engine is running. My understanding of the Lambert device is that it is wired just the opposite; it charges the chassis battery when the motor home is connected to shore power and the battery charger is running.

It seems that I would want to connect the "boost" wire to the house battery to have it act like the Lambert device. Is this correct?

Is there a device that can work both ways? That is, charge the house battery when the engine is running and charge the chassis battery when on shore power and the battery charger is running.

[twinboat]

Take all 3 components out, connect the alternator output to the chassis battery, but the BIM225 isolation solenoid and place the cables on it.

The BIM225 will handle bi-directional charging and boost start function.

Don't get the Li- Bim225, just the standard one, unless you plan on going lithium.

[Monaco_hwy]

I have been digesting what you said. By saying remove the 3 components you mean; the dual battery isolator (on the left), the boost relay (in the middle), and the battery maintainer (top right).

I assume that you mean BGA225 and not BIM225. The BIM225 seems to be for lithium batteries.

I connect the alternator directly to the chassis batteries. The BGA225 will handle the charging of the house batteries, since it will be closed most of the time.

I connect the battery charger to the house batteries. The BGA225 will handle charging the chassis batteries since it will be closed.

I understand that, but what about the boost function? If the BGA225 opens when it detects a voltage of less than 12.2v for the chassis battery how can it perform a boost function? It will always open when you crank the engine.

[twinboat]

Originally Posted by Monaco_hwy

I have been digesting what you said. By saying remove the 3 components you mean; the dual battery isolator (on the left), the boost relay (in the middle), and the battery maintainer (top right).

I assume that you mean BGA225 and not BIM225. The BIM225 seems to be for lithium batteries.

I connect the alternator directly to the chassis batteries. The BGA225 will handle the charging of the house batteries, since it will be closed most of the time.

I connect the battery charger to the house batteries. The BGA225 will handle charging the chassis batteries since it will be closed.

I understand that, but what about the boost function? If the BGA225 opens when it detects a voltage of less than 12.2v for the chassis battery how can it perform a boost function? It will always open when you crank the engine.

Not the BGA, THE BIM 225 Isolstion Manager

You still retain the wiring for the boost terminal of the BIM 225.

[Monaco_hwy]

I read about the BIM and the BGA and I don't understand the difference. Is there some feature that one has that the other does not?

[twinboat]

The BGM225 is a disconnect switch. It manually or automaticly disconnects a battery from a circuit. The BGM senses low voltage and opens its switch, so you don't have dead batteries in storage.

The BIM225 is a battery combiner. It combines one charging battery to the other so both batteries can be charged together, as long as there is a charging source.

It senses voltage above resting voltage ( 13.2 volt or more ) and closes the switch

It does what the battery isolator does now but better. It also does what the Lambert charger does but better. It combines the batteries for boost starting too.

[Monaco_hwy]

OK, I think that I understand.

It seems that you must have a 3 position switch on the dashboard to get all of its functionality. One position connects the control line to ground, this causes the BIM to open. The center position would not connect the control line to anything, this is the automatic function. The third position would be momentary and connect the control line to 12v, this is the BIM close function. In the close position, the BIM connects the 2 batteries together, no matter what the battery voltage. This gives you the "boost" feature.

Is this right?

[THenne1713]

Maybe easiest to just add A BOOST TOGGLE/ROCKER SWITCH at the boost solenoid itself, mine on wall by step (battery under step) on my class-C, (with indicator light) goes from Boost SOLENOID coach battery terminal to BOOST SOLENOID COIL. You will need a ground for the Indicator light? Good Luck.

[twinboat]

Originally Posted by Monaco_hwy

OK, I think that I understand.

It seems that you must have a 3 position switch on the dashboard to get all of its functionality. One position connects the control line to ground, this causes the BIM to open. The center position would not connect the control line to anything, this is the automatic function. The third position would be momentary and connect the control line to 12v, this is the BIM close function. In the close position, the BIM connects the 2 batteries together, no matter what the battery voltage. This gives you the "boost" feature.

Is this right?

The BIM works with out any signal from you, no switch needed.

The only reason for the switch is to override it for boost starting.

Because my BIM keeps all batteries charged, I have never used the boost switch or had a rundown chassis battery.

[THenne1713]

When I looked up BGA225, it also said Lithium on the website I saw... but maybe typo/ web error?