Parasitic Drain, need help September 16, 2025, 01:46:30 am Hey all,I’m in need of some help with dealing a parasitic drain or so I believe. I have a 1989 Lazydaze, e350 econoline. The past few weeks I have been changing alternators, batteries. I currently have a good battery and a good alternator, but there’s still a drain happening where the alternator will not power the battery fully. My engine when off sits at 12.2 and goes down when idle sits a a bit lower.I have gone through my fuse box below the steering wheel and tested all the fuses and as well have used a multi meter there with very little luck.Also, I could not confirm where the Alternator fuse is?I also installed a new external regulator and I intend to replace it tomorrow with a new one after Oreillys said it failed their test. Does anyone know what could be causing this sort of issue? Any help is super appreciated.
Re: Parasitic Drain, need help Reply #1 – September 16, 2025, 11:37:41 am Welcome to the Forum.Have you checked for current flow when the engine is off? Do you own a multimeter that can read amperage?Install the new voltage regulator and see if that is the problem. The voltage should rise as soon as the engine is started.If the voltage sits at 12.2 when the engine is off and the voltage doesn't drop, I would guess there is no drain.Larry
Re: Parasitic Drain, need help Reply #2 – September 16, 2025, 11:48:50 am Quote from: Larry W - September 16, 2025, 11:37:41 amWelcome to the Forum.Have you checked for current flow when the engine is off? Do you own a multimeter that can read amperage?Install the new voltage regulator and see if that is the problem. The voltage should rise as soon as the engine is started.If the voltage sits at 12.2 when the engine is off and the voltage doesn't drop, I would guess there is no drain.LarryThank you!Yes I have a multimeter and read the amperage. The flow at off when checked recently was around 12.2, when the engine is on it dipped down a bit to 12.1 and when the engine is revved it doesn’t increase.We had the guy at Oreillys test and the alternator and battery passed, but the regulator is next. We went around the breaker box with the meter and removed various fuses such as the alarm and instrumental panel illumination. This helped a bit. I will update with more soon as i changed the regulator. Thanks
Re: Parasitic Drain, need help Reply #3 – September 16, 2025, 01:24:55 pm UpdateWe tried a new external voltage regulator and it did not pass the test. The voltage was at 11.8 this time and my battery was drained down to 49% from 65% or so. Keep in mind my battery was disconnected over night as well.The technician suggested to switch brands on the regulator to see if it’s any better. Which I’m trying soon after full charging my battery. The original was a motor craft as far as I know, the last new voltage regulator was also a motor craft and it failed too.
Re: Parasitic Drain, need help Reply #4 – September 16, 2025, 02:03:06 pm Is'nt 12.2 V on a running alternator a little low? I've had a lot of dealings with GM alternators and all run at least 14.4V. I'm not sure that Ford is the same or not. You might consider replacing your alternator yet again with a different brand, some re-manufactured aren't very good at all. Jon
Re: Parasitic Drain, need help Reply #5 – September 16, 2025, 02:09:32 pm Quote from: JonS - September 16, 2025, 02:03:06 pmIs'nt 12.2 V on a running alternator a little low? I've had a lot of dealings with GM alternators and all run at least 14.4V. I'm not sure that Ford is the same or not. You might consider replacing your alternator yet again with a different brand, some re-manufactured aren't very good at all. JonHey Jon, Thanks for the reply. It is low. This is the 3rd one I have gone through with Oreillys and each one has ups and downs. This one is considered good to their tests and it passes. I just installed another regulator and it’s also low. 11.9 when off and then the same when the engine is on and revved. UpdateWould the battery isolator be a possible reason for why the alternator not being able to power the engine battery? When the RV is driven for say 100 miles the house batteries get charged, but the engine battery somehow doesn’t.
Re: Parasitic Drain, need help Reply #6 – September 16, 2025, 04:11:33 pm Hi ValM.; Exactly, it sounds as if the diode going to the chassis battery is open. One diode in the isolator goes to the house batteries, one goes to the chassis battery. This prevents the chassis battery from trying to charge the house battery, and the house battery from trying to run the engine/ chassis. The Ford alternator should run at 14.8 Volts. Disconnect the house batteries temporarily when trying to troubleshoot. Some battery (6 volt pairs) from Lazy Daze came with a shut off switch between the 6v deep cycle batteries. Trying to measure current with a multimeter require disconnection, or a 'clamp on' meter. RonB 1 Likes
Re: Parasitic Drain, need help Reply #7 – September 16, 2025, 07:45:16 pm I'd be curious about the voltage of the coach batteries with the engine running. That should verify that the charging system is actually working, aside from the open connection to the chassis battery.Steve
Re: Parasitic Drain, need help Reply #8 – September 16, 2025, 08:17:08 pm Quote from: Steve TK - September 16, 2025, 07:45:16 pmI'd be curious about the voltage of the coach batteries with the engine running. That should verify that the charging system is actually working, aside from the open connection to the chassis battery.SteveThe house batteries get charged when ever we drive. Surprisingly. It’s just the car chassis battery that will not get the charge from the alternator. They’re 12.7 and fully charged. Two 6vs batteries.Quote from: RonB - September 16, 2025, 04:11:33 pmHi ValM.; Exactly, it sounds as if the diode going to the chassis battery is open. One diode in the isolator goes to the house batteries, one goes to the chassis battery. This prevents the chassis battery from trying to charge the house battery, and the house battery from trying to run the engine/ chassis. The Ford alternator should run at 14.8 Volts. Disconnect the house batteries temporarily when trying to troubleshoot. Some battery (6 volt pairs) from Lazy Daze came with a shut off switch between the 6v deep cycle batteries. Trying to measure current with a multimeter require disconnection, or a 'clamp on' meter. RonB Tried this and still read at 11.9 when idle and revved and with the engine off. I also disconnected everything I could to see if there’s a parasitic draw, but it’s not from the house.Thanks for all the feedback guys, it’s invaluable so far. I’m basically being bounced between Oreillys and AutoZone and neither have a concise answer. I talked to a local RV place and they said the alternator was the blame.
Re: Parasitic Drain, need help Reply #9 – September 17, 2025, 01:06:14 pm I'm with Ron--it sounds as if the isolator is the problem. I'd replace it.
Re: Parasitic Drain, need help Reply #10 – September 17, 2025, 01:15:30 pm It sure sounds like one of the diodes in the battery isolator has failed, as Ron suggested. If so, the starting battery will never get charged; your alternator and voltage regulator may be fine. You can jumper the isolator to test for a blown diode.Have you checked the alternator's output voltage when the engine is running? This can be checked at the isolator, center terminal.When I previously asked about the voltage drain, this is checked by removing one of the battery terminals and connecting one of the multimeter's probes to the removed cable and the other end to the battery terminal. Measure the flow with the multimer set to the 10-amp setting. The engine needs to be off. There should be no current flow or an extremely low flow to maintain the engine's computer memory. I doubt you will see anything since the cause appears to be a bad isolator. A bad isolator would explain your symptomsLarry
Re: Parasitic Drain, need help Reply #11 – September 18, 2025, 09:02:12 am I to am/was chasing gremlins. I made a work around of sorts by using a trickle charger on the chassis fed by the house DC through a inverter. I did find a drain at the radio when off and thus suspected the "isolator" wasn't isolating. The radio drain was solved by disconnecting it (it has an easy disconnect). The downside is I have to reprogram it every time.The isolator looks to feed 3 systems and 2 are identified (radio, Radio/cd) but the third is a mystery and all the wiring disappears into the body. DOES ANYONE HAVE A GUESS WHAT THAT THIRD FEED IS?This problem likely was preexisting as it had a lifeline agm in the engine (12v) which I guessed was the solution for the prior owner? Good for lots of overnight cycles? Anyway my adventure began with the low voltage in the start battery, which a long time later led me to a failing 6v in the house pair (only after replacing the engine battery with a normal one which quickly went dead). I was missing the house battery issue because the solar array kept it topped up during the day and my voltage on the solar display seemed adequate. I added a battery monitor when I changed the house batteries, and now see the excess voltage drains. That was only a few months ago and at the time the consensus was stay with the AGM, but now I see that is no longer the case and I should have gone LI sigh....HELP- WHERE CAN I GET A NEW ISOLATOR FOR A 2007? AND what the heck is that 3rd wire?
Re: Parasitic Drain, need help Reply #12 – September 18, 2025, 12:18:41 pm Etrailer has isolators as well as many other RV suppliers.https://www.etrailer.com/s.aspx?qry=BATTERY+ISOLATORIn our 2003,LD, two wires go to the CB and the dash radioThe third wire goes to the coach battery for charging.Larry
Re: Parasitic Drain, need help Reply #13 – September 19, 2025, 08:38:39 am Thanks Larry!That tracks perfectly, I'll go label the wire until I get a new diode.When I had a dying coach battery it was draining the engine battery (who knew) and thus in the a.m. if I went to start it, low or no go. Start in p.m. ok.Really does explain the AGM they had there. Guess it piggy backed on the house solar recharge through the defective diode.Now I'm wishing I had left it! It was one of those things where I was heading out and wanted to make sure that wouldn't be an issue but it became one anyway.Makes me wonder if that wasn't the better solution (AGM Battery in engine), except for the unknown effects of the solar charger and alternator interacting and/or the generator/alternator running simultaneously?It appears this isn't unusual and likely common but not recognized. Thanks again for the help!!!
Re: Parasitic Drain, need help Reply #14 – September 19, 2025, 01:08:29 pm Hi Val.M; The AGM battery you say that is under the hood for the chassis battery, is still just a lead acid battery. Not to be confused with a lithium battery, AGM is an Absorbed Glass Matt, just a separator between the plates to keep vibration and chunks of lead sulfide or (sulfate) from breaking off and falling to the bottom to short out internal cells. Other than that it is just like any other (maintenance free) lead acid battery. You might be able to replace a diode in a diode isolator, but generally it is a 'potted' assembly and both diodes are replaced as a unit. Amazon.com: Victron Energy Argofet Battery Isolators 200-2AC (2 Batteries... This should be similar to what you have. RonB As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
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