Boost Solenoid

[bigwally2]

hey everybody,im working on an 86 beaver marquis with a 3208t cat deisel,just finished the throttlebody gaskets...runs great but am losing charge for starting...found the isolator cracked and just replaced..am lookin at replacing the boost solonoid was wondering about rating as i have a 160amp alternator,so would a 160 amp solonoid work? continuous?...i get 11.5 volts at the starter post through the rear station start solonoid i have 13.5 at the chassis battery without boost....everything clicks but the starter wont turn....i have no spark at the chassis battery terminal when i test it for draw but i do get a spark at the coach battery ground with every thing off??any help would be greatly appreciated,Steve in nj

[RV Wizard]

Hello and We are glad to have you join us here and we look forward to reading of your adventures and experiences. I am sure you will enjoy our website and forums. Good luck, stay safe and keep us posted.

Not knowing your electrical skill level there could be several components that could cause this problem. First, check all battery termianal and chassis frame ground connections. Check for charging from the engine alternator with engine running; you should have about 14.2vdc. Once batteries have been fully charged with an outside charger, check batteries to be sure they are good. If not replace them and trouble shoot charging with engine running once again. Once this section is charging properly then you should check to see if there is any charging from the shore power incoming voltage source; you should have 13.8 vdc or better if batteries are slightly discharged. Have someone activate the boost start switch on the dash and check to see if the batteries are interconnected by a rise in voltage on the lower initial voltage bank from the higher voltage bank. If so, the boost solenoid is good. At this point, if the chassis battery bank is not being charged from shore power you could diagnose as to why by starting at the chassis battery bank and working backwards or just add something like an Echo charger. Let us know what you find along the way and we will try to be of more help.

[Kiawah]

would a 160 amp solonoid work?

The solenoid connects the two battery banks together, it's not limited by the alternator capacity. It should be rated at least as the same as that cable is fused, typically 300-400 amps.

Connecting a dead battery bank, with a charged battery bank, is going to shoot a LOT of current across that cable.

[TQ60]

That year braver with 3208 is likely on gillig chassis.

You have a pair of batteries on each side and isolator on passenger side.

Drivers side is starting batteries and should be connected direct to starter.

The rear run panel does have disconnect but that is for everything but starter.

11.5 volts at the starter when trying to start is great but if starter not operating sounds like bad starter but not enough info to call that.

Google cat 3208 starter troubleshooting to see what needs to be checked, no time now to get our manual.

Regarding boost selenoid you need huge one...

You can check with gillig as the chassis may be MHA and they support it but not sure if they or the coach builder installed the secondary batteries.

Others will provide help and will check in after work.

[bigwally2]

thanks very much for the imput...slowly getting my electrical bearrings (figuratively) i noted 12.6 volts from the chassis side of the isolator to the ground post on the chassis battery and 13.8 on the coach side of the isolator to the ground post on the chassis battery,with shore power connected.i also got continuity on the primary coil on the starter,12.6 volts on the starter hot post to the starter ground post....it seems the hot and ground on the starter are sound,the primary gets a 11.5 volt signal from the remote solonoid on the rear control panel but no internal reaction at the starter......like you guys said things are pointing to the starter....should i jump the hot post to the starter motor feed to see if the motor will operate? if so how with a large screwdriver? will it make sense to bring the starter to a shop to have the solonoid side rebuilt?cost wise? thanks again for your time and experiance

[TQ60]

Is selenoid on starter then it is a servicable part.

It may come off starter in place but better to remove.

If a jumper wire to selenoid post from battery post does not spark then coil open.

If it sparks and no movement actuator may be stuck and easy fix.

Smack the side of the selenoid lightly with a hammer a couple times.

If it works then pull starter and clean it up inside selenoid.