Community Forums

Jerry226 · 12-09-2017, 04:18 AM

I was leaving home to go to florida and I noticed my amp meter on dash was only on 10.5 volt. I called a truck repair shop thinking I need a new alternator because my batterys were not charging.They checked the alt. and said it was putting out good. I have 2 trays of batteries. 1 for house and 1 for coach. He put a wire between both sets of batteries and they both started charging. He said to buy this part when I got to florida and both sets of batteries would charge ok. I don't know what to ask for to buy this part. I have a 1997 magna with series 40 detroit . any help would be appreciated. I was told but forgot. I will write it down this time if someone can help. (getting old sucks).

tmw188 · 12-09-2017, 04:56 AM

Relay? Did he point it out to you , if so take a picture of it.

pumper9x9 · 12-09-2017, 05:24 AM

Try giving the guy a call. Can't hurt, might help, and it would be a great crowd pleaser.

twinboat · 12-09-2017, 05:47 AM

Was it a 150 or 200 amp " Isolator " ?

https://www.rvupgradestore.com/160-A...1026046173CC0D

Jerry226 · 12-09-2017, 05:49 AM

Quote:

Originally Posted by tmw188

Relay? Did he point it out to you , if so take a picture of it.

He said it was under the coach close to the batteries. I cant look for it until it stops raining.

Sbrownstein · 12-09-2017, 05:53 AM

If he used a piece of wire and both banks started charging, it is probably the battery isolation relay, but they are all different so you age going to have to go looking to find out which one you need.

Jerry226 · 12-09-2017, 05:59 AM

Quote:

Originally Posted by twinboat

Was it a 150 or 200 amp " Isolator " ?

https://www.rvupgradestore.com/160-A...1026046173CC0D

That's it. thank you so much. will check what size when it quits raining.

Fredward · 12-12-2017, 11:58 AM

Something doesn't quite make sense here to me. The gauge on the dash usually is for the chassis batteries which are charged directly by the alternator. First question is: was the engine running when you saw the low reading? The Isolator generally is installed between the chassis and house battery banks. It keeps the house batteries from dragging down the chassis batteries when the engine if shut off. So if the engine was running, the gauge reads low and the batteries test fine; I would suspect the gauge on the dash.

On my 2000 Magna, the gauge on the dash is usually wrong. I use the VMSpc application to monitor voltage and it is always between 12.8v and 13.4v with engine running. I think you have a gauge problem. Could be bad ground.
Fred

twinboat · 12-12-2017, 12:18 PM

Quote:

Originally Posted by Fredward

Something doesn't quite make sense here to me. The gauge on the dash usually is for the chassis batteries which are charged directly by the alternator. First question is: was the engine running when you saw the low reading? The Isolator generally is installed between the chassis and house battery banks. It keeps the house batteries from dragging down the chassis batteries when the engine if shut off. So if the engine was running, the gauge reads low and the batteries test fine; I would suspect the gauge on the dash.

On my 2000 Magna, the gauge on the dash is usually wrong. I use the VMSpc application to monitor voltage and it is always between 12.8v and 13.4v with engine running. I think you have a gauge problem. Could be bad ground.
Fred

Mechanical isolators work as you described, connecting the 2 battery banks together.

With solid state isolators of many older MHs, the alternator output is connected only to the center terminal and the battery banks are connected to each output terminal.
They work like electric check valves, letting the current flow out from the center to both banks, but do not let any current back thru.

Jerry226 · 12-13-2017, 07:39 AM

Quote:

Originally Posted by Fredward

Something doesn't quite make sense here to me. The gauge on the dash usually is for the chassis batteries which are charged directly by the alternator. First question is: was the engine running when you saw the low reading? The Isolator generally is installed between the chassis and house battery banks. It keeps the house batteries from dragging down the chassis batteries when the engine if shut off. So if the engine was running, the gauge reads low and the batteries test fine; I would suspect the gauge on the dash.

On my 2000 Magna, the gauge on the dash is usually wrong. I use the VMSpc application to monitor voltage and it is always between 12.8v and 13.4v with engine running. I think you have a gauge problem. Could be bad ground.
Fred

my amp guage has always read 13 to 13.5 and it went down to 10.5. when they tied both banks of batteries together the guage went back to 13+. Right or wrong that is what happen. I drove from Indiana to florida without problems. So I plan on getting another isolator when I find out the one I need to get. Thanks for the imput.

Jerry226 · 12-13-2017, 07:44 AM

Quote:

Originally Posted by twinboat

Mechanical isolators work as you described, connecting the 2 battery banks together.

With solid state isolators of many older MHs, the alternator output is connected only to the center terminal and the battery banks are connected to each output terminal.
They work like electric check valves, letting the current flow out from the center to both banks, but do not let any current back thru.

Thanks twinboat what you said makes sense and describes my problem. I love this site and I always get my questions answered.

Sbrownstein · 12-13-2017, 07:53 AM

Quote:

Originally Posted by Jerry226

my amp guage has always read 13 to 13.5 and it went down to 10.5. when they tied both banks of batteries together the guage went back to 13+. Right or wrong that is what happen. I drove from Indiana to florida without problems. So I plan on getting another isolator when I find out the one I need to get. Thanks for the imput.

OK, I thought I was following all of you until now. First, the indication was that it was a diode isolator block. This is not a dynamic solution, in other words, the banks are always tied together for current flowing from the alternator to the batteries.

Now I am assuming that you mean a battery voltage meter and not an ammeter. On my 1996 Bounder I would always watch for the voltmeter to "quiver" within 15 seconds of starting when my battery control center fired the isolation relay. Perhaps that is what you are referring to. But if that is the case, you have an active BCC and not a diode isolator.

twinboat · 12-13-2017, 01:46 PM

Quote:

Originally Posted by Sbrownstein

OK, I thought I was following all of you until now. First, the indication was that it was a diode isolator block. This is not a dynamic solution, in other words, the banks are always tied together for current flowing from the alternator to the batteries.
.

Diode isolators are nothing more then 2 high amp diodes potted in a heat sink.

On many occasions, when the isolator fails, it burns out 1 of the diodes. As long as the other, in this case the output to the house bank, is still good, the alternator will charge that bank.

Of course you wouldn't know that because the chassis battery is not being charged and the dash mounted volt meter will be dropping.

The mechanic tied the charging house battery to the chassis battery, so they both charged.

Ilvmygt · 12-14-2017, 10:06 PM

On my 2000 Magna there is an isolation relay located in the last compartment on the passenger side. It ties the chassis battery to the house battery when the oil pressure reaches 15 psi to charge the house batteries while the engine is running. It is also used as the "boost" relay when you need house batteries to start the engine. If I remember correctly it was a 200 amp relay. I don't have the part number but when I get home in a couple of days I can look it up if you want. It is a White-Rodgers relay.

My dash gauge also reads low when compared to the actual battery voltage.

Frank