Battery Boost Won't Work

[JnJnKatiebug]

Went out to start the MH yesterday and the batteries were low. Hit the boost switch and nothing. I put my jumper cables from the house batteries over to the starter batteries and it cranked right up. I used the boost switch late last summer and it worked fine. I have not had time to check it out. Where would be the best place to start looking for the problem? Is there a fuse?

Batteries are six years old now and they are down after 3 to 4 weeks of sitting even with the disconnect turned off. Probably need batteries in the spring but for now I am leaving the charger/maintainer on it.

[Ivylog]

If you have a BigBoy relay in the rear electrical box, check that you can hear it click when someone hits the boost switch. If it clicks then the contacts need to be cleaned/filed as you can take it apart. Unhook both sets of batteries as it's a tight fit getting it out and you do not need to arc weld anything. If it does not click then call Monaco for wiring help.

[crasster]

Assuming you have a boost relay, the house batteries must have enough juice in them (crank amps) to switch the relay or to kick on the starter motor.

[pianotuna]

Hi,

If the chassis batteries were totally flat they might not be able to energize the boost relay.

The relay may have burned contacts.

Can you hear the relay activating when you press the boost switch?

[The_Texan]

It is the relay located in the battery compartment, on the back wall. It is a Trombetta model 010, with copper contacts. Make sure you replace it with the 020 model, which has silver alloy contacts.