What is this relay and what does it do?

[Orrin]

2002 HR Ambassador with 8.3 Cummins. The house batteries are not charging when driving, I don't know that they are supposed to. Would it have anything to do with this relay? How do I test it? Seams easy enough to change and particularly hard to replace. As usual any help is always appreciated.

 

[Fish]

My house batteries charge while driving after my chassis batteries are completely charged.

Since both banks of batteries are connected to it, looks like the switch that combines the battery banks when you hit the battery boost switch. I think that along with an IRD or BIRD is what would direct charge from your alternator to either battery bank, but I'm new to this.

Do your chassis batteries charge off of shore power? Mine don't. If they do you have a BIRD, if they don't you have an IRD. At least that's my understanding.

 

[Orrin]

My house batteries charge from shore power or from the generator, but don’t charge from the main diesel alternator. I don’t know if they are supposed to.

 

[RV Fam65]

Hello.
Fish is correct. Based on how it looks to be wired, that is likely a “battery boost” relay (activated via rocker switch on dash). I believe our house batts are charged via engine alternator, but I’m not sure. There is a separate disconnect relay for our house batteries; it’s inactive when connected to shore power since our shore power charges the house batts.
Let us know what you find. ?

 

[Orrin]

What is an IRD or BIRD?

 

[Fish]

What is an IRD or BIRD?

IRD is Isolator Relay Delay, it's part of what charges the house batteries from the alternator when your chassis batteries are completely charged.

BIRD is Bidirectional Isolator Relay Delay, it allows the same as the IRD but also will charge chassis batteries from shore power.

The info at this link explains it pretty good: Intellitec IRD

 

[Orrin]

Fish, thanks for the information, really helps.

 

[Buly]

Orrin,
On a side note, you should take care of the cables connecting your batteries, and all other connections. They look so badly corroded, that if it was me, I would replace them all. With low voltage systems, clean contacts are very important.

 

[Orrin]

Thanks Buly.