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tomgrigsby · 09-18-2019, 05:32 PM

Something strange is going on with my BIRD. In the 3 months that I've owned the coach, I always just turned off the chassis battery cutoff (BCO) switch and plugged the unit in to keep the coach batteries charged. A couple of weeks ago I realized that the BIRD should also keep the chassis batteries charged, so two weeks ago I left the BCO switch on. Went out to start the coach Sunday, and you guessed it, won't start. Chassis batteries low. Tried the boost switch and it didn't help even though coach batteries show fully charged on the panel.

Started troubleshooting and found the battery boost switch fuse (15a) at the BIRD was blown. Replaced the fuse but it didn't make any difference. So I buttoned things up, BCO off, put a trickle charger on the chassis batteries and went for some wine.

Yesterday went out to check things out, and when I went into the coach, the ScanGauge D was powered up. That was strange because I thought the BCO was off. Coach was plugged in to shore power, by the way. So, put the key in and coach started right up. Turned it off and double checked the BCO and it was OFF! I pulled the fuse back out of the BIRD boost switch and that turned the ScanGauge D off and everything was back to (ab)normal.

So, I have some troubleshooting to do. I know someone has been into the wiring as the dealer had to replace the converter twice before I bought the coach. The first converter died because the former owner had jumpered some wire to it from the battery. So I have a mystery as to why the BIRD doesn't charge the chassis battery, why the boost switch doesn't work, and why the coach would start with the boost switch fuse in and BCO off when the coach is on shore power.

By the way, went for a drive tonight and nothing seems to have been damaged from starting it with the BCO off.

Just though some might be interested in this mystery. Any thoughts and suggestions are welcome of course.

twinboat · 09-18-2019, 07:10 PM

The BIRD is working and the solenoid is too.

Your charging of the house batteries is bringing the volts up above the point that the BIRD is closing the solenoid ( same solenoid as the boost circuit ).

When you are starting the engine, you are starting it from the house batteries.

The boost/isolation solenoid can work sporadically when the contacts are burnt. That may be why it doesn't always work.

If you disconnect your shore power, run the surface charge off the house batteries, it probably not start with the chassis switch off.

RKins · 09-19-2019, 05:34 AM

You're going to have to bring a voltmeter with you next time. Tell us what you measure on each stud of the big combiner relay that the BIRD controls.
When connected to shore power and charger working properly, you should see above 13.3V on the house bank and one side of the big relay. That is what the BIRD needs to see to activate the big relay to combine the house and chassis banks and you will read the same voltage on each stud.

"007" · 09-19-2019, 09:49 AM

Welcome to the forum if didn't already.
First off you always have the BCO on at all times using the coach or connected to at least 110 volts.
The BCO will not register volts or operate the solenoid if house batteries are low.
With the BCO on the house batteries will charge first than when at full charge will shift to chassis batteries to fully charge.
BIRD's, B.I.M. and batteries are explained in this sticky more fully.
When you not plugged in to 110 your alternator will be charging all your batteries when driving but in reverse your chassis battery than your house batteries.
Sounds like everything is working OK just remember to have BCO ON.
If you make a mistake again a 12v battery charge will charge faster not a trickle charger, the BIRD will do the control function.

tomgrigsby · 09-19-2019, 11:42 AM

I plan to get back out there with a meter and an assistant this weekend. Clearly something is working because when on shore power I could start the engine with the BCO off. However, initially the battery boost switch fuse was blown and when I replaced it the switch still didn't do anything. I'm not a little confused over why there even IS a 15a fuse for the boost switch. Maybe it was the blown fuse that kept the system from charging the chassis batteries on shore power?

tomgrigsby · 09-20-2019, 10:02 AM

Quote:

Originally Posted by tomgrigsby

I plan to get back out there with a meter and an assistant this weekend. Clearly something is working because when on shore power I could start the engine with the BCO off. However, initially the battery boost switch fuse was blown and when I replaced it the switch still didn't do anything. I'm not a little confused over why there even IS a 15a fuse for the boost switch. Maybe it was the blown fuse that kept the system from charging the chassis batteries on shore power?

Welp, looks like there's nothing wrong with the system other than I had a blown fuse labeled "Battery Boost Switch" at the BIRD. Checked chassis battery voltage, plugged in shore power, and checked again. Batteries show 13.77 or so. Appreciate the input from all.

BPoland · 09-20-2019, 10:38 AM

Also, remember that the Battery Boost switch, just connects the house to the chassis batteries. the effect is not instantaneous. You may need to hold the boost switch down for 30 seconds to a minute for enough current to pass into the chassis battery to make a difference.

RKins · 09-20-2019, 01:45 PM

Quote:

Originally Posted by tomgrigsby

Welp, looks like there's nothing wrong with the system other than I had a blown fuse labeled "Battery Boost Switch" at the BIRD. Checked chassis battery voltage, plugged in shore power, and checked again. Batteries show 13.77 or so. Appreciate the input from all.

That's good to hear. You measured from ground to each of the big posts on the combiner relay? When operating correctly, the voltage should be the same on each (if the voltage on the house post is above 13.3V).

Qwert66 · 09-22-2019, 08:49 AM

A simple resistance check across the big studs on your combiner solenoid (when closed) will tell you if their dirty and need cleaning.

RKins · 09-23-2019, 04:59 PM

Quote:

Originally Posted by Qwert66

A simple resistance check across the big studs on your combiner solenoid (when closed) will tell you if their dirty and need cleaning.

I agree but I don't think I would try that while the system is connected.

Qwert66 · 09-23-2019, 05:08 PM

No problem doing the resistance check while connected and requires no removal of wires. A basic understanding of I=E/R is in order here.

tomgrigsby · 09-23-2019, 05:39 PM

Appreciate all the help and suggestions. I was an Aviation Electronics Tech in the Navy and know my way around a multimeter, and the voltage test suggestions are spot on. One tip though. Resistance tests must be done on unpowered circuits or you could let the magic smoke out of your meter. The meter uses it's own battery voltage to measure resistance, so any power on the contacts will at best give inaccurate results, and may well toast your meter.

RKins · 09-24-2019, 06:51 AM

Quote:

Originally Posted by tomgrigsby

Appreciate all the help and suggestions. I was an Aviation Electronics Tech in the Navy and know my way around a multimeter, and the voltage test suggestions are spot on. One tip though. Resistance tests must be done on unpowered circuits or you could let the magic smoke out of your meter. The meter uses it's own battery voltage to measure resistance, so any power on the contacts will at best give inaccurate results, and may well toast your meter.

Yep, that was what I was getting at.

Qwert66 · 09-24-2019, 06:56 AM

For this specific case I stand by the comment that disconnecting the solenoid power is not necessary and in fact energizing the coil is necessary to close the contacts prior to checking. I agree sometimes in other situations power can influence resistance checks. If it makes you feel better you can disconnect one of the large cables on the solenoid but it is not necessary. Yes I am a EE professional certified electricial engineer with a 30 year career in Automotive.