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Billy , Trainer/ Master Technician
Category: Audi
Satisfied Customers: 3498
Experience:  Trainer 8+ years, master tech. 10+ years, SAE member
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Audi A4 Quattro Avant: I found your site through a search which

Resolved Question:

I found your site through a search which turned up the query about a 2002 Audi A4 Avant tailgate problem. My Avant of the same year has what sounds like a very similar issue. When I unlock the car centrally using the fob, and then go to open the tailgate by depressing the latch under the number plate, it may open normally the first time I do this in the day, but on subsequent attempts, the gate will not open, and manual use of the key is required. My research on the issue made me think that the "tailgate actuator" was the cause of the fault, so I dropped the trim (as in your previous instructions) and observed the sequence directly. Normally, the actuator withdraws the locking lever from the latch, when the handle is pressed. The next times, the actuator does not withdraw quite the full distance, and so the rod does not move far enough to open the latch. I removed and dismantled the actuator, to see how it worked. The small electric motor inside seemed without any obvious fault, and when I applied DC to the terminals with it removed, the motor worked perfectly. The associated spring loaded pinion, which withdraws the latch rod, was undamaged, and seemed to work perfectly in passive simulation. I reassembled the actuator and reinstalled, but the same latch behaviour persists.
I am wondering what particular fault within the actuator could be the issue. I am now questioning whether it could be a problem with the microswitch in the latch itself, which is perhaps not applying power to the actuator for long enough.
Can you give me any insight into this problem. I do not want to exchange the actuator (very expensive here in New Zealand) if it is not really the issue. However, I do not know whether the microswitch could be the cause and whether it is amenable to being dismantled and replaced. I would be most grateful for your advice .
Kind regards,
Peter Charlesworth
Submitted: 3 years ago.
Category: Audi
Expert:  Billy replied 3 years ago.
Hello Peter and welcome! I'm Billy and i will assist you with this.

First i would check the power getting to the actuator, as if you have some dirty contacts, the actuator will get lower voltage and do this. The second thing to check would be the time the actuator is getting pulse... is it longer on the first time, or not... in which case, the central locking (body control module) would require an updated software. If the actuator is getting good power supply, and sometimes working as it should, sometimes not. Try spraying some Wd40 or equivalent, make sure it is working on the latch before installing the trim (try it a few times). IF you have good power supply, and the actuator still does not work all the times, then, this would require replacement.

Thank you for your trust! Get back to me if you need more assistance...Thank you in advance for the positive rating...

Regards, Billy
Billy, Trainer/ Master Technician
Category: Audi
Satisfied Customers: 3498
Experience: Trainer 8+ years, master tech. 10+ years, SAE member
Billy and 2 other Audi Specialists are ready to help you
Customer: replied 3 years ago.

Dear Billy,

Thank you for your reply and the suggestions. However, you do not mention which "dirty contacts" you have in mind, or how I might check the "time the actuator is getting the pulse". I have checked the actuator function under direct vision many times, triggered by pushing the release catch on the outside of the tailgate. Subjectively, the tactile feeling I get when activating the catch is somewhat variable, but I am not sure whether this indicates any inconsistency in the internal function of the catch. I believe that it contains a microswitch, which is one place that there might be "dirty" or damaged contacts. You do not say whether the catch can be disassembled to examine the internal switch, and this sort of information would be most helpful. I am aware that if I take the car to my local Audi serviceman, the approach will simply be to replace "units", without any attempt to "repair" the problem. Perhaps this is the only practical way, but I am trying to save myself a substantial bill by attempting to analyse the situation in more detail. I would appreciate your further comments, and perhaps more specific instructions to complete the steps you mentioned.

Thanks for your assistance,


Expert:  Billy replied 3 years ago.
Hello Peter,

The contacts would be on the connector of the actuator itself and on the switch or release switch, i would also check the wiring where it enters the tailgate (on top near hinges, remove sleeve for access).
Checking the time, with a led test or a multimeter, make sure it is getting the same pulse everytime (for 1second, 2 seconds etc..), as if it getting a faster pulse when not operating correctly, it would not be the actuator causing this. The release catch can get pushed inside when operated repeatedly, and this would not mean anything, unless, when you feel it differ, you get a different pulse (and the actuator would not work fully), then the release catch or switch would require replacement (that is not very likely).
Indeed, Audi dealers would replace units (save labor, and the cost is on you).
This model has a water ingress problem (very common) to the body control unit, which is in the front foot well (you'll have to check both sides under the carpet). Make sure the contacts there are also clean and tight, with no moisture or water signs.
The catch does contain a microswitch, however, these are molded into one unit, so i'm afraid that the only way to dismantle would be by breaking.

I hope this is clear enough... get back to me with your findings, or if further details are needed.

Regards, Billy
Customer: replied 3 years ago.

Thanks Billy, that gives me some very clear things to consider.

I'm pretty sure from my previous examination that the contacts on the outside of the actuator are fine. Someone posted on another forum that he had dismantled the actuator motor and found copper dust which, when removed, solved the fault. Although I inspected the individual components inside the actuator, I did not attempt to open the motor. I may consider doing that if it looks like my only remaining option is to buy a new actuator...nothing to lose! I will test some of your other ideas tomorrow.



Expert:  Billy replied 3 years ago.
You're most welcome!

Make sure that you check the body control module. And indeed, as a last resort, i would pry open the motor assembly. Hopefully we'll get the fix before that.

Regards, Billy

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