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Discussion Starter · #1 ·
I am so frustrated. I have a 2019 Ascent premium.

I have a hitch and a 4-prong towing wire installed already, that someone else did.

I found out this morning that I can drive three hours away and get a 16’ Airstream Bambi tomorrow but I have to have a 7 prong plug and brake controller.

I have been to three places (inc. the dealership) today trying to get this done. Dealership had no clue and told me to call hitch places. Hitch place “guessed” at what they would need, gave me a $436 quote and told me to come back in 2 weeks. UHaul told me it would be around $80 for the wires and then whatever cost for a brake controller, but they don’t have the wires in stock.

I’ve been on camping world website, O’Reilly, and Discount auto parts websites and can’t Figure out what I need. I’ve been all over this forum, and it seems like all the answers are there but in a language I don’t understand.

Please, someone take pity on me and give this to me simply. I promise I’m not an idiot and I don’t know why this is confounding me.

I need to know:

1) what do I need in order to turn my 4-prong female connector into a 7 blade connector. Do I unplug the existing 4 prong and plug something else in? If so, do I attach the 3 extra wires to things that already exist or do new wires need to be pulled from the engine to the back of the car? (This is what the 1st hitch place said and quoted).

2) what do I need to do to attach a brake controller? I’ve read about there being a connection under the dash, and I know generally where they’re talking about but there’s a LOT of wires under there. If I get a wireless brake controller, is that easier? The UHaul place had a Tekonsha prodigy for ~$250- do I get that?

3) is there any hope of me getting this done by tomorrow (I.e. can I reasonably do this myself, once I get the right parts?

thank you anyone who is willing to donate some time to un-tangling my head.

skwilson
 

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The tekonsha prodigy P3 is a good brake controller (I have that one). There are many threads on installing that in this forum, with pictures to help find the wiring harness which is to the left of the brake pedal, often behind the panel there.

Usually when a hitch is installed, both a 4 prong and a 7 prong are installed. Are you sure the 7 prong isn't there behind a cap? It should be to the left of the hitch.

I believe the Ascent is prewired to support the 7 prong, so if you don't already have one, you should be able to plug it in with the right adapter.

Did you get the OEM subaru hitch? Or a 3rd party hitch?


Pics of your hitch in the back would help too.
 

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I am so frustrated. I have a 2019 Ascent premium.

I have a hitch and a 4-prong towing wire installed already, that someone else did.

I found out this morning that I can drive three hours away and get a 16’ Airstream Bambi tomorrow but I have to have a 7 prong plug and brake controller.

I have been to three places (inc. the dealership) today trying to get this done. Dealership had no clue and told me to call hitch places. Hitch place “guessed” at what they would need, gave me a $436 quote and told me to come back in 2 weeks. UHaul told me it would be around $80 for the wires and then whatever cost for a brake controller, but they don’t have the wires in stock.

I’ve been on camping world website, O’Reilly, and Discount auto parts websites and can’t Figure out what I need. I’ve been all over this forum, and it seems like all the answers are there but in a language I don’t understand.

Please, someone take pity on me and give this to me simply. I promise I’m not an idiot and I don’t know why this is confounding me.

I need to know:

1) what do I need in order to turn my 4-prong female connector into a 7 blade connector. Do I unplug the existing 4 prong and plug something else in? If so, do I attach the 3 extra wires to things that already exist or do new wires need to be pulled from the engine to the back of the car? (This is what the 1st hitch place said and quoted).

2) what do I need to do to attach a brake controller? I’ve read about there being a connection under the dash, and I know generally where they’re talking about but there’s a LOT of wires under there. If I get a wireless brake controller, is that easier? The UHaul place had a Tekonsha prodigy for ~$250- do I get that?

3) is there any hope of me getting this done by tomorrow (I.e. can I reasonably do this myself, once I get the right parts?

thank you anyone who is willing to donate some time to un-tangling my head.

skwilson
I believe they sell a 4 prong to 7 prong adapter. Camping World, maybe Cabela's, maybe even WalMart or Home Depot may carry them. Is this trailer from a dealer or a private sale? I would think a dealer would be able to help you. Is there an Airstream dealer near you or where you are buying?

Sorry I can't give you a definite answer, only some suggestions. Are you rushing into buying this trailer or have you been researching? Sounds a little fishy in a way that you have to pick it up tomorrow, one day notice.

Hope it works out for you.
 

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A 4 prong to 7 prong adapter would let you plug it in, but it would NOT actually enable the brakes which is what you need for a larger trailer.
 

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Discussion Starter · #5 ·
It was 3rd party from eTrailers I believe. I definitely do not have the 7prong installed already.

I’ve found what I believe is both built-in connectors (both white square plugs). The one in the back under the storage tray has five wires going to it. That’s what the current 4prong wire is plugged into. The one under the dash I can’t tell how many wires it has, but it’s the same square white plug and it’s exactly where the verbal descriptions say it would be (I can’t find the actual photos folks have referred to in multiple posts).

I’ve now been told I only need a 4-prong to 7-prong “adapter”? That all the functions will still be available. I don’t know if this is correct.
 

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Discussion Starter · #6 ·
I believe they sell a 4 prong to 7 prong adapter. Camping World, maybe Cabela's, maybe even WalMart or Home Depot may carry them. Is this trailer from a dealer or a private sale? I would think a dealer would be able to help you. Is there an Airstream dealer near you or where you are buying?

Sorry I can't give you a definite answer, only some suggestions. Are you rushing into buying this trailer or have you been researching? Sounds a little fishy in a way that you have to pick it up tomorrow, one day notice.

Hope it works out for you.
I’m not buying yet, this is a favor to let me try out a trailer similar to one I might order. The ASs currently have a 6 month lead time and no dealer within 8 hours drive of me have any on the lot of the little size I’m wanting. I don’t actually know if the size will work for me, so I really need to try it before I plop down a deposit and order one. The time constraint is mine - work starting back soon and school for kids, this is my only chance for 3+ months, and I only found out this am I could use it.
 

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I’ve now been told I only need a 4-prong to 7-prong “adapter”? That all the functions will still be available. I don’t know if this is correct.
No, that is incorrect. The brakes will not function with an adapter.
 

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These products from etrailer solved my similar problem. The videos are very helpful. Essentially, the existing four pole plugs into the product creating both a new four pole and a new seven blade. Word of warning: running the 12 gage wire from the harness, through the vehicle, and to the battery was a chore, but it’s essential for powering electric brakes which the AS Bambi will definitely need.


As for the brake controller, I love love love this wireless, Bluetooth enabled product. Just goes in between the trailer and vehicle plugs; no need to install/wire a brake controller. There are mixed reviews but mine works flawlessly. You use the app to set the braking sensitivity and application force.


Good luck and stay safe.
 

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All Ascents sold that are Premium, Limited or Touring, already have the body harness ran. You just needed a connector plug and to plug in your 4 or 7 pin connectors to it.

The Base does not have the body harness, but absolutely is not designed to tow a Bambi.

These products from etrailer solved my similar problem. The videos are very helpful. Essentially, the existing four pole plugs into the product creating both a new four pole and a new seven blade. Word of warning: running the 12 gage wire from the harness, through the vehicle, and to the battery was a chore, but it’s essential for powering electric brakes which the AS Bambi will definitely need.


As for the brake controller, I love love love this wireless, Bluetooth enabled product. Just goes in between the trailer and vehicle plugs; no need to install/wire a brake controller. There are mixed reviews but mine works flawlessly. You use the app to set the braking sensitivity and application force.


Good luck and stay safe.
 

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Do you have a friend with a truck? I don't think its realistic that you will have what you need by tomorrow unfortunately. If you tow that airstream without functioning trailer brakes you are putting yourself and everyone else on the road at risk.
 

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You CANNOT adapt a 4 to 7 pin connector. 7 pin has brakes and a power wire. The lights would work, but you woudl fail to stop, because most 7pin trailers, use electric brakes.
 

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Whomever installed your hitch setup clearly didn't use the OEM kit as it includes both the frame integrated hitch receiver and both the 4 and 7 pin connectors. To get a brake controller to work you need to have a 7 pin connection properly installed, preferably something that integrates with the OEM harness points so that you can also use the connector under the dash, driver's side, to plug in the brake controller you choose to use.

The "easiest" solution is to replace what you have with the OEM hitch receiver kit, but that's certainly not inexpensive when you take into consideration the cost of the kit plus the labor for installation. I do not recall if there is a part number to order just the wiring portion of the kit from Subaru...perhaps someone else can say if that's something available.
 
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I am so frustrated. I have a 2019 Ascent premium.

I have a hitch and a 4-prong towing wire installed already, that someone else did.

I found out this morning that I can drive three hours away and get a 16’ Airstream Bambi tomorrow but I have to have a 7 prong plug and brake controller.

I have been to three places (inc. the dealership) today trying to get this done. Dealership had no clue and told me to call hitch places. Hitch place “guessed” at what they would need, gave me a $436 quote and told me to come back in 2 weeks. UHaul told me it would be around $80 for the wires and then whatever cost for a brake controller, but they don’t have the wires in stock.

I’ve been on camping world website, O’Reilly, and Discount auto parts websites and can’t Figure out what I need. I’ve been all over this forum, and it seems like all the answers are there but in a language I don’t understand.

Please, someone take pity on me and give this to me simply. I promise I’m not an idiot and I don’t know why this is confounding me.

I need to know:

1) what do I need in order to turn my 4-prong female connector into a 7 blade connector. Do I unplug the existing 4 prong and plug something else in? If so, do I attach the 3 extra wires to things that already exist or do new wires need to be pulled from the engine to the back of the car? (This is what the 1st hitch place said and quoted).

2) what do I need to do to attach a brake controller? I’ve read about there being a connection under the dash, and I know generally where they’re talking about but there’s a LOT of wires under there. If I get a wireless brake controller, is that easier? The UHaul place had a Tekonsha prodigy for ~$250- do I get that?

3) is there any hope of me getting this done by tomorrow (I.e. can I reasonably do this myself, once I get the right parts?

thank you anyone who is willing to donate some time to un-tangling my head.

skwilson
if you are not up to a DIY per forum instructions, most every area has a auto shop that specializes in electrical work. Just bring them the wiring and a printout from the forum and they can do the rest.
 

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This is just a general observation and comment.

Do not evaluate a major purchase under a crisis deadline. Especially when the evaluation has technical installation work involved. Especially when it should be alert-evaluative driving, what is supposed to be a test drive situation. You can't evaluate the trailer or your car properly if you are run into the red at your wits end from trying to pull this all off in a day.

Take the next available scheduling opportunity to pull the trailer. In the mean time get your Ascent set up properly. Then you can evaluate the trailer in the real world.

BTW, a set of CKE sway bar bushings would help out your situation either way...(shameless shill that I am sometimes)
 

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You already got the advice you need here. And even if it might not be impossible it is highly unlikely to get it done in time. Do not rush this would be my advice as well!

Rent a tow capable Pick-up truck from U-Haul instead (make sure it has a break controller and let them show you how it works) and get the trailer if that is really your only chance to do this tomorrow. Keep your speed at 55mph. You haven't mentioned if you have towing experience in general as it is a serious endeavor not to be rushed into. Figure out your Ascent situation later. My 5cents.

Also your dealership is lame as they should know what Robert.Mauro is saying and finding that harness (the backend, you found the front end) and getting a 7 plug connected would be your best shot (then you still need to buy and install the brake controller). Any other Subaru dealers in your vicinity?
 

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Here is a picture of the front connector. The back one you said you found where the 4 pin is connected. I'm not sure if that is the same one where the 7 pin connects. I would assume it is a second one since the OEM hitch has both a 4pin and a 7 pin plug.
4906
 

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You will need to purchase specialty adapters to do this without having to splice wires.
I know I am super confused because I read around everywhere and was told by Subaru that I need to run a hot from the battery to the back and use a connector like you mentioned above. I even looked at it and found the current flat 4 where it is hooked up but didn't see the 7 way like on Robert's PDF showed..

So the 7 way connector is just down the wiring harness further than the 4 way hookup? No need to run a separate hot? Is the harness a standard connector for most 7 way plugs?
 
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