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Hitch install on a 2007 A4 Cabrio

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by jimrob, Mar 17, 2014.

  1. jimrob
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    jimrob New Member

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    [Mar 17, 2014]
    Last April I bought my 2007 Audi A4 Quattro Cabrio because I wanted to downsize from having a BMW 330xi and a BMW 325i convertible. This car gave me the best of two worlds. The one thing I had missed greatly with the Audi was not having a trailer hitch on it for towing my motorcycle on vacation. (Before you say why don't you buy a SUV for towing. I already have a truck that I use for plowing and hauling my boats around. I do not need another vehicle to maintain.)

    The main problem was finding a hitch that would work on my car. Not one American company makes a hitch that will work on this car. I decided to go overseas to buy my Westfalia hitch from a company in the UK. I used this company https://www.pfjones.co.uk/ and all I can say is that they are great to deal with. The price was incredible compared to buying that part here and the shipping was 2 days over the pond. I was told up front that the hitch was not a simple install because my car is not a European version. The US models have stringent bumper regulations and such which makes this hitch a bit difficult to install. I had no clue as to what I was in for.

    Instead of the normal 2 hour install it took me about 4 hours to do this install. I will provide all the information as to what I had to do to make this work for my car. If anyone has any questions please feel free to email me for help.

    To start off with you need to remove the lever for lifting up the convertible top space box.
    Remove the L shaped flap after that.

    Remove the two sides of the trunk interior.

    Remove the amplifier on the right side and the plastic box on the left side. This gives you access to 4 of the bolts that hold on the rear bumper face.

    Remove the 2 screws on each side of the rear inner wheel well that hold the inner fender liner in place. Bend the liner inwards to remove the 4 screws on each side that hold the edge of the bumper to the body support.

    Remove the 8 bolts inside the trunk that hold the bumper face to the rear of the car. Pull out the two sides of the bumper slightly and remove the bumper face.

    Remove the two bolts on the aluminum bumper support where it is attached to the bumper impact gas shocks.

    Inside the trunk remove the 4 bolts that hold these shocks in place.

    The new hitch will not fit into the slots where these gas shocks came out of. The right side on the 2007 has a restriction in it. I think the black box is in there and sealed up.

    You will need to remove about 5 inches from the length of the right side of your hitch. I used a Sawzall to cut mine off. Now remove the round spacer from this cut off section by cutting the weld on the spacer. I used a 3 inch air grinder with a cut off wheel to do this.

    Measure the original bumper holes inside the trunk of your car. Using this dimension mark out a new hole on the trailer hitch on the right hand side that you shortened up. Drill out the hole to the proper size. I used a 5/8 drill bit for my new hole. The hole needs to go through both sides of the hitch rail.

    Weld in the spacer that you removed from the cut off rail section.

    On the left inside of the trunk you need to remove a piece of body tape about a foot forward from the rear bumper hole. This is your new bolt hole for the hitch on the left side.

    On the right side you will be using the two original holes to mount the hitch. Paint up any bare spots on the hitch and install the hitch into the frame rail holes using the new bolts and washers (supplied). You will need two people to install the forward bolt on the left side because it is almost impossible to hold the nut above the muffler heat guard and turn the bolt inside the trunk. Make sure you put a large flat washer (included with the parts) on the underside of the car on that bolt.

    You will now have to remove the 16 rivets that hold the inner support on the aluminum bumper face bar. I ground mine off and banged the rivets out. Fit this to your hitch by cutting out a small area in the center to fit around the center portion of the hitch. Install the bolts to hold that on.

    You can now install your bumper face using the (8) inner nuts and install the inner wheel well screws.

    Leave the trunk apart to do the wiring. I purchased a separate trailer wiring plug from Advance Auto that wires your separate directional's and brake lights through a sensor to a 4 terminal plug for the trailer. I haven't installed that yet.

    The last thing left to do is to cut out a small section on the bumper in the very center to make room for the removable hitch and knob. Jim

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    Last edited: Mar 17, 2014
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  3. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Mar 17, 2014]
    Can I suggest you split up your text a bit :)
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  4. jimrob
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    jimrob New Member

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    [Mar 17, 2014]
    Would you like it split up into different posts or just broken up into paragraphs?
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  5. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Mar 17, 2014]
    lol, just paragraphs would be more legible for others to read IMHO.
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  6. jimrob
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    jimrob New Member

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    [Mar 17, 2014]
    How's that? let me know if you see anything that is too confusing.
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  7. NHN
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    [Mar 17, 2014]
    That's allot better, not for me, just looks & reads easier mate for any site visitors, thanks for putting the time in :)
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  8. hades-
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    hades- Yorkshire & Humber Rep. Regional Rep VCDS Map User

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  9. jimrob
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    jimrob New Member

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    [Mar 17, 2014]

    If I can save anyone a lot of time and hardship to do this conversion then it is well worth it to me.
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  10. Marklar
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    Marklar New Member

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    [Mar 17, 2014]
    Well done, Jimrob! I have the same Westfalia towbar on my 2008 cabrio but unlike you, I chickened out and had it installed together with the dedicated electrics by a local specialist.

    Initially there was a problem in that the car seemed to 'forget' that it was a cabrio and although the roof would operate correctly, the 'roof operating' dashboard light and warning messages had disappeared.

    The local Audi dealer gave me loads of grief about the computer having been 'hacked' by a non Audi-authorised person and said that the only way to restore the system would be to hook into the Audi computer in Germany, delete the whole programming from my car and then reprogram it to original factory specification. Naturally, vast amounts of cash would be transferred from my bank to theirs for the privilege.

    In the end the fitters and Westfalia organised for me to visit the people who program Westfalia's hand-held coding units. When I told their expert what Audi had said, his reply was brusque and to the point. "Bull****!" was all he said.

    Literally in the time it took us to drink a cup of coffee the car was sorted, tested and returned to us in perfect working order, all free of charge. When I said how impressed I was, the modest reply was, "All I did was change a couple of numbers. It's no big deal."

    I think what had happened was that the towbar fitters' handset had reprogrammed my car as if it were a saloon or Avant model. It was the first cabrio they had worked on. Anyway, all works well now but it just goes to show how arrogantly unhelpful and downright rude the main agents can be.

    Audi with towbar.jpg

    Audi without towbar.jpg
    Last edited: Mar 17, 2014
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  11. jimrob
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    jimrob New Member

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    [Mar 17, 2014]
    It appears that you have the European version Audi. Was your right frame rail open, unlike mine? I couldn't use the European wiring harness. Over here we have a 4 plug trailer harness for our trailer lights with trailers that do not have electric brakes or separate turn signals with separate brake lights. The electrical wiring I bought has a modulator for the turn signal/brake lights switching to keep from back feeding into the other circuits. I wonder why the computer was messed with to begin with when the electrical harness was installed. I agree with you on the dealer issue. Many of them are all about the money. The Audi dealer near me is pretty good.
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  12. Marklar
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    Marklar New Member

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    [Mar 18, 2014]
    Yes my car is UK specification but I'm afraid I cannot answer your query re frame rails, after all I did say that I'd chickened out of doing it myself.

    The European trailer socket and my caravan both have 13 pin connections and I use an adapter to connect my trailer which has a seven-pin socket.

    My understanding is that when the new electrics pack (a major bit of computer kit) is installed, the ECU has to be coded to accept it. Once this is done the car automatically detects when a trailer or caravan is connected (via light bulb resistance I think, older systems had a microswitch in the socket) and puts itself into 'trailer stability mode'. It also turns off the rear parking sensors, car reversing light and car rear foglight and illuminates the trailer turn indicator light on the dashboard.

    All of the above worked fine first time but the recoding as a non-cabrio must have switched off the roof monitoring system. As I said, it was a simple fix for someone who knew what he was doing but well beyond the capabilities of a main dealer who, to be fair to them, must only rarely experience such problems.
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  13. jimrob
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    jimrob New Member

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    [Mar 18, 2014]

    That is interesting that the car can be re-programed to do all of that. I don't have the parking sensors on my car. I did hear that they need to be disabled when towing a trailer of any sort. I have parking sensors on my pickup truck and need to switch it off on the dashboard or it will keep right on beeping. I'll be wiring up my plug this coming weekend. I'll post if there are any issues with messages or anything not working right.
    #12

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