7 pin connector fuse

[ReneGingras]

We picked up our trailer 2 weeks ago in Chilliwack. I had to replace the 7 pin connector 15 amp fuse twice since then, after driving about 1000 km, with a 2023 Subaru Ascent. Has anyone encountered this problem before? Any idea what to do besides keeping a box full of spare fuses?

 

[C&G in FL]

Specifically, what fuse are you referring to? There is no “7-pin connector” fuse. Most vehicles have multiple fuses, not a single fuse, related to the functions provided by the 7 wires in the mix. It would help to know which function (lights, 12v auxiliary, etc) is requiring fuse replacement, and when the fuse is blowing. For example, is it blowing at random times or at a specific time such as when the umbilical cord is plugged into the tow vehicle?

 

[Chamberman]

We picked up our trailer 2 weeks ago in Chilliwack. I had to replace the 7 pin connector 15 amp fuse twice since then, after driving about 1000 km, with a 2023 Subaru Ascent. Has anyone encountered this problem before? Any idea what to do besides keeping a box full of spare fuses?

Assuming you're talking about the 12v power to the trailer?


Are you trying to operate your Fridge on 12V power while driving? If so, Don't.... Not with only a 15A fuse in the line. It draws too much amperage to operate on 15A.

If you're not operating the fridge on 12V power then what if anything are you operating?

 

[ReneGingras]

Specifically, what fuse are you referring to? There is no “7-pin connector” fuse. Most vehicles have multiple fuses, not a single fuse, related to the functions provided by the 7 wires in the mix. It would help to know which function (lights, 12v auxiliary, etc) is requiring fuse replacement, and when the fuse is blowing. For example, is it blowing at random times or at a specific time such as when the umbilical cord is plugged into the tow vehicle?

In the fuse box under the dash, there's a fuse named "trail" and is the one that has blown twice at random times. Replacing it and everything works again, ie. lights, breaks, etc. I read in the Escape manual that the circuit should be protected by a 30 amp fuse...that could be the problem.

 

[ReneGingras]

Assuming you're talking about the 12v power to the trailer?


Are you trying to operate your Fridge on 12V power while driving? If so, Don't.... Not with only a 15A fuse in the line. It draws too much amperage to operate on 15A.

If you're not operating the fridge on 12V power then what if anything are you operating?

It's a 2-way fridge, so no 12V. Besides the trailer breaks, the lights and possibly the DC charger, I can't see anything else using power.

 

[MrLynn]

In the fuse box under the dash, there's a fuse named "trail" and is the one that has blown twice at random times. Replacing it and everything works again, ie. lights, breaks, etc. I read in the Escape manual that the circuit should be protected by a 30 amp fuse...that could be the problem.

Escape may say '30A', but Subaru may specify only 15A; best to check. Could be Subaru didn't anticipate a trailer as big as a 21C.

 

[Chamberman]

It's a 2-way fridge, so no 12V. Besides the trailer breaks, the lights and possibly the DC charger, I can't see anything else using power.

The electric brakes require approx 3A per brake at their maximum, i.e. max braking force. The battery while charging can draw whatever your wiring (or the resistance within it) and alternator can deliver.

Its very likely that the Subaru trailer 12V circuit is wired with 14 or even 16 gauge wiring which isn't capable of handling 30A service and this is why its safety fused for 15A. You should get on the Subaru forums to see if anyone has posted about this. If this is the case then you're going to need to run a new circuit with wiring capable of handling 30A service (10 Gauge) if you want the trailer to operate as intended via the 7 pin connector and not blow fuses.

 

[ReneGingras]

The electric brakes require approx 3A per brake at their maximum, i.e. max braking force. The battery while charging can draw whatever your wiring (or the resistance within it) and alternator can deliver.

Its very likely that the Subaru trailer 12V circuit is wired with 14 or even 16 gauge wiring which isn't capable of handling 30A service and this is why its safety fused for 15A. You should get on the Subaru forums to see if anyone has posted about this. If this is the case then you're going to need to run a new circuit with wiring capable of handling 30A service (10 Gauge) if you want the trailer to operate as intended via the 7 pin connector and not blow fuses.

Do you think that a RV shop can run a new circuit, if I find one on my way?

 

[Chamberman]

Do you think that a RV shop can run a new circuit, if I find one on my way?

If they're competent they should be able to do this for you. Do you know if your Subaru has an ignition relay on the 15A circuit for the trailer? If there's a relay there then the new circuit can use a standard automotive 30A relay and use the switched 12V from the current 15A circuit to turn on the 30A relay. Doing this will maintain the protection from overdischarging the Subaru's 12V battery when parked. If there is no relay in place then I'd have the shop add one and find a 12v switched circuit to drive the newly added 30A relay from.

An alternate thing that you could do to maintain your 15A circuit is to add one of the Victron DC to DC chargers. The Victron 12/12 9amp would effectively limit the charging current to your trailer but still give enough juice to keep the battery topped off. The 12/12 9A is a bit quirky in that you have to have the battery disconnect off when it powers up, then you can switch the battery on to begin charging. This particular Victron unit doesn't like to have voltage on its output when it turns on, doing so keeps it from charging. I know this because I have one in my trailer and only found out about this issue after installing the unit. Its well documented on the victron forums.

Personally I'd have the 30A circuit installed and if the shop isn't capable of installing a relay too, then just get the 30A service wired in and be careful to unplug your trailer when you stop for long periods. Then in the future once you're home you can search out a well versed shop that can install the switched 12v relay for you.

 

[daveandalice]

I see the Ascent forum has a thread about the 15 amp fuse problem, there's talk about unplugging the plug before using the electric tongue jack.

https://www.ascentforums.com/thread...-camper-car-or-travel-trailer-at-fault.19875/

 

[Chamberman]

I see the Ascent forum has a thread about the 15 amp fuse problem, there's talk about unplugging the plug before using the electric tongue jack.

https://www.ascentforums.com/thread...-camper-car-or-travel-trailer-at-fault.19875/

Yes, that will help. Also having the battery fully charged before you plug the trailer harness in will also help.