Fuse? for 12V on 7 pin trailer connector

davedave · 11-15-2018, 09:39 AM

I have a Jayco 2015 Precept 31UL, Ford F series Super Duty chassis, Triton V10. I used the 12v from the 7 pin trailer/towed car connector on back of Rv to keep Car battery changed. Worked good, than lost the 12 v power at connector. Other lits still work.
Talked to Jayco factory, checked fuses in panel under hood, all ok. Must be another fuse, I have look in Ford manual, can not find it.
Any ideas where it is?

MikeThompson · 11-15-2018, 10:04 AM

I may be wrong, but I think it's a relay, not a fuse. See if you can find a diagram online.

RoyBraddy · 11-15-2018, 11:29 AM

On my FORD F150 series it is the fuse panel over the top of the radiator. Has a fuse and a RELAY. The FUSE and RELAY was in my glove box which was unmarked on what it was for... My ignition has to be 'ON' to provide 12VDC back to my POPUP trailer. In the owners manual it is all called 'trailer tow' I think...

Don't know if all of that is different for the larger trucks or not...

Roy Ken

Vicr · 11-15-2018, 02:29 PM

Ray, the OP has a Ford F-53 motorhome chassis so nothing like the F-150.

Davedave, check your Ford manual as I would think there is a fuse in a chassis fuse box for the 12v charge line going to the 7 pin since that line is on the load side of the alternator. There are also a few supplemental fuses near the battery and Jayco may have source the charge line there.
Also, there is a Facebook Precept and Alante page that now has 350 followers and you may get a more accurate response there.

NickM · 11-15-2018, 09:27 PM

I thought I had lost my 12V line back in the summer and searched high and low for a fuse but never located one. Had a lot of people point me in several directions but they all proved fruitless.

Ford says it is up to the body installer to add the 7 pin circuits. Jayco says it comes that way from Ford.

I tend to believe Ford just because the chassis arrive at Jayco and have that lonnnnnngg extension added behind the rear axle at a local shop. I have seen both the stock chassis and altered chassis when I took the factory motorized tour last year. Wish then I had know to ask that question.

I'm using that 12V line to charge my CR-V battery so it would be nice to know where it originates and how it is protected.

jasum · 11-16-2018, 07:39 AM

Quote:

Originally Posted by davedave

I have a Jayco 2015 Precept 31UL, Ford F series Super Duty chassis, Triton V10. I used the 12v from the 7 pin trailer/towed car connector on back of Rv to keep Car battery changed. Worked good, than lost the 12 v power at connector. Other lits still work.
Talked to Jayco factory, checked fuses in panel under hood, all ok. Must be another fuse, I have look in Ford manual, can not find it.
Any ideas where it is?

On the F350 SuperDuty it is under the hood against the firewall and a real PITA to get to.

NickM · 11-16-2018, 07:56 AM

Guys,

Just like Vicr posted above, F series pickup trucks have no relevance to the OP's question. Please try to stay on topic.

Vicr · 11-16-2018, 11:17 AM

Quote:

Originally Posted by jasum

On the F350 SuperDuty it is under the hood against the firewall and a real PITA to get to.

This is a motorhome forum not an F series truck forum. Please be relevant.

jasum · 11-16-2018, 02:35 PM

Quote:

Originally Posted by vicr

this is a motorhome forum not an f series truck forum. Please be relevant.

really??

NickM · 11-16-2018, 03:32 PM

Yes, really.

If you spend enough time here you see people replying with non relevant comments on travel trailers and fifth wheels.

Class A owners come here to seek help with issues, me among them and non-relevant comments just tend to clutter the forum.

There is a lot of combined experience within the Jayco forums which can make life easier for those seeking help and advice.

hawkster · 11-16-2018, 05:45 PM

Well said, NickM.

Vicr · 11-16-2018, 05:55 PM

Quote:

Originally Posted by hawkster

Well said, NickM.

Hi mark! Do you have any ideas where the charge line is derived from? I'm trying to remember if anyone on the Facebook Precept and Alante page has posted anything on the subject.

hawkster · 11-17-2018, 06:21 AM

Quote:

Originally Posted by Vicr

Hi mark! Do you have any ideas where the charge line is derived from? I'm trying to remember if anyone on the Facebook Precept and Alante page has posted anything on the subject.

Hey Vic, not for sure. My precept is at the dealer for a month or six weeks for minor repairs or I would look. I just use the four pin connector which I believe has left, right, running, and stop lights. This goes to pass thru lights on my Grand Cherokee.

Someone on facebook did have a connection problem in the rear harness and repaired it.

Octane Shane · 11-28-2018, 11:47 PM

This site might help.
https://www.autogenius.info/ford-f-5...e-box-diagram/

NickM · 11-29-2018, 12:24 PM

Thanks Octane Shane, I think I went through pages similar to this for my 2016 F53 and checked all the fuses related to 12v trailer tow but they were all good. This was back about mid summer.

This was back when I was having house battery problems and after replacing the batteries I had 12V back on the 7 pin. What I plan to do is have DW watch my meter and progressively remove all the trailer tow related fuses one at a time to see if voltage goes away.

davedave · 11-29-2018, 02:39 PM

I want to thank all who gave input to this problem. I also spend time talking with Jayco service hot line.
Things lead to the Trailer Charge Relay or also called Tow Plug Charge Relay. This is located in the battery compartment.
Once I located it I remember the factory recommended changing one of leads from this relay to solve a problem with the house batters draining during storage even with the 12v disconnect switch off.
Went back to original wiring, all OK.

Again thanks for all you input.

NickM · 11-30-2018, 07:42 AM

Quote:

Originally Posted by davedave

I want to thank all who gave input to this problem. I also spend time talking with Jayco service hot line.
Things lead to the Trailer Charge Relay or also called Tow Plug Charge Relay. This is located in the battery compartment.House battery compartment?

Dave, So am I to understand that the wire from this relay to the 7 pin plug has no fuse protection?

Once I located it I remember the factory recommended changing one of leads from this relay to solve a problem with the house batters draining during storage even with the 12v disconnect switch off.

Can you provide more detail here? Even though I will install a battery disconnect switch I would like to understand about changing leads and which relay.
Went back to original wiring, all OK.

Again thanks for all you input.

Thanks in advance Dave,

davedave · 11-30-2018, 08:18 AM

Nick
Yes the house battery compartment.
The diagram Jayco service sent shows no fuse. This is a diagram "Harness, rear lights and trailer connector"
It shows the power( red/black lead) to the "Trailer charge relay" from a 30 amp circuit breaker.

Hope this helps

NickM · 11-30-2018, 06:16 PM

Dave,

That's great news, at least they have a circuit breaker protecting the lead.

Is there a place to post drawings from Jayco? I have a 120V coach wiring and 12V coach wiring from Jayco for a 2016 Precept 35S.

davedave · 12-01-2018, 10:31 AM

Nick
The issue is no one knows where the circuit breaker is. There is a 30 amp fuse # 13,in Ford's controller module under the hood, it is labeled " Trailer tow electric break" that is were the factory sent me when I first tried to solve the 12v problem. I never could fine any other reference in Fords manual that would give me more infor. about the 30 amp circuit breaker.
I just pulled that 30 amp fuse, still have 12v t o the 7 pin connector on back of RV.
Also I can't understand how Jayco is using the "Trailer Batt charge Relay". This relay is always on, not controlled by the chassis ignition or house shut off switch.
I an not an expert on RV wiring. but I do understand control circuits and electricity.

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