2nd battery charging?? 2009 E350 5.4

happycampingcouple · 08-19-2019, 04:50 PM

2009 E350 Extended Body 5.4, 2 wheel drive

I replaced the house battery on my frame rail last year (group 27 Marine Battery, I think) and installed a fuse, on/off switch and 12 v power block. Battery is charged by the stock Ford Battery isolater under the engine battery...

We went camping a couple weeks ago and noted the digital meter I installed read 12.7 Volts. I used my 12V Cpap adapter and woke up the next morning to read 12.3 volts on the meter.

I ran the engine for about 30 minutes and checked the meter again... 12.3v

I used the CPAP again two more nights and the volt meter reads 12.3

We drove home 2 hours and I hoped it would be ok.

Drove 5 hours to our next camping trip and voltage reads 12.0v after the long drive and back to 12.0 after running my cpap all night...

Where should I start??

marret · 08-19-2019, 05:53 PM

Doesn't sound like the house battery is being charged.

Have you confirmed switch is on?

It charged before you installed the new hardware? If so check your wiring, you may ha ve made a mistake.

When the van is running, or after you turn it off, do you here the isolater click?

Have you checked the house battery voltage with a meter with the van runninh?

happycampingcouple · 08-20-2019, 12:06 PM

Marret, Thanks for the reply.

I checked voltage engine off at the distribution box I installed and read 11.89v, My hardwired meter reads 12.0. I started the engine, same readings.

I checked the starting battery while running and reads 14.0 or so...

I checked all the tow fuses and anything that had to do with the aux battery and they were all fine....

One of the wires on the isolater (under the starting battery was slightly loose, I tightened and rechecked everything... No change...

Would you think its the isolater itself? I dont have anybody here at my house today, so I cannot tell if I hear a click when the engine is starting...

If it is the isolater, anyway to test it? Please dont tell me this is a dealer only thing!!

Camping trip on Friday!!!

Thanks again for the help!

TomsBeast · 08-20-2019, 01:35 PM

I'd recommend a basic test: first isolate the house battery from the rest of the system, (remove the negative cable from it's post, leave the positive connected). Check the house battery voltage while disconnected and note. Check for charging voltage at the still disconnected house battery cables (with engine running, and then turned off). Depending on the type of isolator you have, while the engine is off, the house battery negative cable disconnected, the voltage at the cables should show zero, no voltage. Engine running and negative still disconnected, you should have a healthy charging voltage like 13.7 ish at the still disconnected house battery cable. If while engine running, disconnected cables show zero charging voltage, I'd investigate the isolator, the house battery grounding at the frame, the house battery positive cable connections at both ends (the cable that goes between the battery and the isolator, #6 gauge on my rig) Hope that helps

happycampingcouple · 08-20-2019, 02:47 PM

Thanks Toms beast,

I went to my local Ford dealership and asked the parts guy to look it up... He was absolutely no help... Unfortunately, I know more about this van than he does!!

I went home and removed the isolater under the starting battery. Now I have a part #... I put it all back together and will try to locate another isolater...

I am not good at this stuff... I am hoping a new isolater will do the trick... Any favorite places to try to locate the part???

Its Part # f8ub-14088-aa

marret · 08-20-2019, 02:48 PM

Agree with TomsBeast for further checks.

If 0 on the disconnected cables, might try checking voltage at the isolater positive cable connection.

Edit, I see you posted again while I was posting.

Common recommendation for replacement is BlueSea ML-ACR 7622 or 7620.

https://www.bluesea.com/products/762..._-_12V_DC_500A

gahamby · 08-20-2019, 03:17 PM

Look here. A true font of wisdom.
http://www.sportsmobileforum.com/for...ches-7991.html

happycampingcouple · 08-20-2019, 03:33 PM

Thanks for the info. I ordered a new solenoid... I could not find the part number I removed from my van, so I chose the Motorcraft sw5181 ... Amazon and will be here in 2 days... I'll pray this works and let y'all know if it worked.

Thanks again

Mike

TomsBeast · 08-20-2019, 04:15 PM

f8ub-14088-aa is a Ford starter relay.

You are sure that's not your starter relay, but a Ford starter relay being used as a battery isolator? (some upfitters do used starter relays for isolating batteries) If your house battery is wired to that particular starter relay, it's a safe bet it is being used for isolation, but it's worth confirming.

Did you determine that it's bad?

RV's often use a large relays, starter relays sometimes, to isolate the engine battery from the house battery.

Word is, big relays don't suffer a voltage drop like the diode type of isolator, but they do have internal contacts that wear out and quit working.

Typically, if an RV manufacturer or conversion upfitters uses a starter relay, it's one that's rated for 'continuous duty' (a problem with older RV's and conversion vans, sometimes a repair gone astray, were some of the older relays weren't rated for the heat load of continuous use.

happycampingcouple · 08-20-2019, 04:28 PM

Tomsbeast,

I have no idea what Im doing here... The read somewhere that the isolater that charges the stock aux battery on my frame rail is located under the starting battery.

Funny thing is I cannot locate that part #f8ub-14088-aa for sale any where... I looked up the starting solenoid on some part websites at it points to the Motorcraft SW 5181, that is the one I ordered....

This is all stock on my van. Its never been converted by anyone other than me...
I dont know if mine is bad, but I think I checked as much as I could...
I am def out of my league with this elec stuff... I just need to charge the battery under my van so I can run my CPAP this weekend!!!

Thanks again