Community Forums

chillwill · 07-27-2016, 05:39 AM

Thank you all for your assistance. I removed the battery isolator on yesterday and awaiting the new one to arrived today for install. Right now I'm in the phase of process of elimination.

Quote:

Originally Posted by twinboat

Good point about the high current.

I should have said, remove and combine the 3 wires on one post or use jumpers with ring terminals.

twinboat · 07-27-2016, 06:19 AM

Quote:

Originally Posted by chillwill

Thank you all for your assistance. I removed the battery isolator on yesterday and awaiting the new one to arrived today for install. Right now I'm in the phase of process of elimination.

If you have a DuVac system and not working correctly, keep an eye out for an overcharging condition. The overcharging can cause the isolator to fail, along with other problems.

Isolators can be checked with an ohm meter. Current only flows from the center post to the side posts, not the other way.

Dr4Film · 07-27-2016, 06:36 AM

Quote:

Originally Posted by chillwill

Need your help. My alternator is not charging my engine batteries. 2 brand new L/N alternator installed and both or not charging. At Love's mechanic shop and after going through all the possible issues we came to the conclusion that the battery isolator is bad. Someone please help. Batteries are good.

Were the LN Alternators the correct model number for your coach?

What is the model number of the LN Alternators that you have attempted to use on your engine?

What was the model number of the failed alternator that was removed?

Dr4Film ----- Richard

wolfe10 · 07-27-2016, 07:53 AM

Reasonably too late, since you have already removed it, but troubleshooting a battery isolator is pretty simple.

Said another way, I hate to see you diagnose by buying parts.

Troubleshooting an alternator/isolator (assuming diode-based battery isolator):

Make sure all connections at alternator and isolator are clean and tight.

With the engine at high idle (1000 RPM or so), check for voltage between ground and center lug of the battery isolator.

If 14.5+, check from ground to the two outer lugs on the isolator. Should be about .7 less than at the center lug. So 13.8- 14.2.

If you do not have the correct reading at the center lug, check at the alternator B+ terminal. If still not correct, either a wiring issue (sense wire and/or IGN hot wire if you have one) or alternator.

If correct reading to isolator center lug, but not on one or both outer lugs, the isolator is bad.

Brett
2003 Alpine 38FDDS

chillwill · 07-28-2016, 06:02 AM

Both alternators that was on the coach are L/N 2824LC. I had the first one replaced in April which worked out fine. Took a few trips after that and everything was working ok. Voltage was good. Last trip was last week and that's when I noticed the voltage issue. I stopped and checked the wires and everything was tight and looking good. Got back on the road the voltage didn't change but after a few miles the voltage went back to normal. When I stopped for the night and restarted the coach, the voltage dropped again. Replaced the alternator with a new L/N 2824LC (under warranty) and it was reading the same. (What's the chance of having 2 bad alternators. It's possible). The LOVES Tech checked the wiring and recharged my batteries and found no issues. That's why I've narrowed it down to the battery isolator. I have a 2001 Alpine Coach 350 cummins.

Quote:

Originally Posted by wolfe10

Reasonably too late, since you have already removed it, but troubleshooting a battery isolator is pretty simple.

Said another way, I hate to see you diagnose by buying parts.

Troubleshooting an alternator/isolator (assuming diode-based battery isolator):

Make sure all connections at alternator and isolator are clean and tight.

With the engine at high idle (1000 RPM or so), check for voltage between ground and center lug of the battery isolator.

If 14.5+, check from ground to the two outer lugs on the isolator. Should be about .7 less than at the center lug. So 13.8- 14.2.

If you do not have the correct reading at the center lug, check at the alternator B+ terminal. If still not correct, either a wiring issue (sense wire and/or IGN hot wire if you have one) or alternator.

If correct reading to isolator center lug, but not on one or both outer lugs, the isolator is bad.

Brett
2003 Alpine 38FDDS

twinboat · 07-28-2016, 06:16 AM

They are using DuVac Alternators. If the new isolator don't fix it, have them recheck the wiring. Also look for a DuVac fuse somewhere.

chillwill · 07-28-2016, 07:20 PM

Ok everyone, the new isolator didn't fix it. So now I'm still banging my head on what could be the issue. I also have a Big Boy Battery Isolator Relay. I guess I will look at it next. Checked all the wire and fuses and everything seems okay. Thanks for the assist so far.

Quote:

Originally Posted by twinboat

They are using DuVac Alternators. If the new isolator don't fix it, have them recheck the wiring. Also look for a DuVac fuse somewhere.

twinboat · 07-28-2016, 07:57 PM

Get it to someone who knows the system.

Did you jump the isolator wires to see if it charges.

chillwill · 07-29-2016, 05:39 AM

No I didn't jump the isolator wires because I don't understand the procedure.

Quote:

Originally Posted by twinboat

Get it to someone who knows the system.

Did you jump the isolator wires to see if it charges.

twinboat · 07-29-2016, 06:32 AM

Take the wire off the post marked chassis or engine battery and put it on the post marked ALT. or alternator, with the wire already on there.

You will have 1 empty post and the center post will have 2 wires.

Just to be clear, this is a battery isolator. Is this what you have ?

RSchleder · 07-29-2016, 06:54 AM

Quote:

Originally Posted by chillwill

GM RV Nation. Need your help. My alternator is not charging my engine batteries. 2 brand new L/N alternator installed and both or not charging. At Love's mechanic shop and after going through all the possible issues we came to the conclusion that the battery isolator is bad. Someone please help. Batteries are good.

Perhaps starting a new thread would have been a good plan instead of jumping on one that's a couple of years old. Just a suggestion for the future.

wolfe10 · 07-29-2016, 08:03 AM

Again, strongly suggest that you troubleshoot it vs throwing parts at it.

Start at the alternator B+ to ground. If 14+ VDC there with engine at 1000 RPM, keep going until you do not see charging voltage.

Next place to check is the battery isolator. Center lug (from B+) should read the same as alternator B+. The outer lugs about .7 VDC less.

If OK there, move on to the batteries/fuses to batteries if you have them.

Brett
2003 Alpine 38FDDS

chillwill · 07-30-2016, 05:29 AM

Yes that is what I have. There is no post on there marked chassis or engine. It's battery 1, alternator, battery 2.

Quote:

Originally Posted by twinboat

Take the wire off the post marked chassis or engine battery and put it on the post marked ALT. or alternator, with the wire already on there.

You will have 1 empty post and the center post will have 2 wires.

Just to be clear, this is a battery isolator. Is this what you have ?

twinboat · 07-30-2016, 06:12 AM

Quote:

Originally Posted by chillwill

Yes that is what I have. There is no post on there marked chassis or engine. It's battery 1, alternator, battery 2.

Ok, plug it in and get the house batteries charging. Check the volts, batt. 2 should be the house and will be higher then chassis batt.

Or, unhook the start battery and see which one goes to 0 volts.