Fuel Filler door actuator electrical issue

Thought I posted this last week, but it is still not up there . . .
2001 Jetta TDI, 290,000 miles. My fuel filler door is not opening. Pulled the plug to the actuator and put a meter on it. It is getting voltage when the driver door mounted switch is pulled. So I replaced the actuator. No luck. Took both the old and new actuator into my workshop and gave them 12 v. from a power supply--both work.
On the chance that for some reason the plug and actuator were not making good contact (yes I cleaned the contacts) I got hold of a new plug. Still no joy.
Suggestions? Is it possible the interior door switch is sending enough voltage for my meter to read it, but not enough amperage to operate the actuator?
Thanks

Possible but more than likely you just have a poor ground. Check to see if the catch on the door has worn a groove in the actuator. If it has the door may be what stops the actuator from moving. Good luck.

a good ground is a must to check and others have found exactly what you suspect. switch resistance letting voltage thru but not enough amperage.

The actuator works when 12v is supplied by a power source in my workshop. It is not mounted to anything at that point, so one of the wires is clearly the ground. When connected to the plug in the trunk, the actuator does not work, whether it is mounted to the chassis or just hanging there. Again, I assume it is grounded via the wiring. I have ordered a new switch since that would seem to be the only thing left that could cause the actuator not to work in the system.

I'm not an electrical engineer, but I've never before heard of a switch not letting "enough amperage" through. If the switch is dirty or if there's a bad ground, it will reduce the voltage, which will increase the amperage in the circuit. Would someone please enlighten me?

I had the same issue on my Golf. Actuator started taking several tries to get it to pop, then finally nothing. I pulled the connector at the actuator, saw I had 12v when the switch was pressed and assumed the actuator was bad.

Picked up a used one, installed it and - nothing. Crap!

Checked the old and new actuators by giving them 12v directly from the battery, both worked.

Turned out, the switch was bad. I was seeing 12v at the actuator connector but that was with no load. The internals of the switch were likely badly corroded, meaning that it was unable to pass enough current under load to operate the actuator.

Simple to test. Pop the door panel off. Pull the connector off the fuel door switch.
There are four wires in the connector. Use a short length of wire to connect terminals 1 (RED/YELLOW) and 2 (BLUE/RED) together. The grey/blue and brown wires are for the light bulb - DO NOT mess with those, you could blow a fuse! Be careful!

If the actuator pops - you've got a bad switch.

Kicked myself for not doing a proper diagnosis the first time.

I was able to access the switch without pulling the whole door panel. I removed the three lower screws and upper Phillips screw. I then pried at the bottom until the panel popped out of the clips. Laid down on my back under the door and was able to reach up and access the connector to do the test.
Replacing the switch without pulling the panel can be done, but it's a hassle as you have to use a couple of small screwdrivers to release the tabs that hold the switch into the door panel.

think of electricity like a garden hose with a faucet on one end and a spray nozzle on other end. Volts is pressure and amps is water flow. open the faucet with 20 psi and you can use the spray nozzle to wash something. but if the faucet is only barely cracked open the hose will still have full pressure in it if the spray nozzle is not being used. but even with full pressure in hose there is no water flow if you try to use the spray nozzle.

when you say if voltage drops then amps increase, that is if your are maintaining the same wattage. P=IE

dirty, corroded connector or contact will increase resistance thereby reducing amperage. E/R=I

showing full voltage but not having enough amperage due to dirt or corrosion is very common. I am chasing this kind of problem at work every week. even an old battery that needs replaced will show 12 volts but will not flow amperage because of corrosion on the lead plates.

Got it. Thanks for the explanation.

A new switch did fix the problem.
Not a difficult job. Just apply a steady firm downward pressure to the switch--it will unseat and drop down into the panel. I did remove the upper set of window switches and three phillips #3 screws behind it, then the three t20 screws at the panel base. Also 1 short phillips screw on the upper right side near the tweeter (some posts said this is a torx, but not on my 2001). Popped the panel away from the door but did not remove it. Loose enough for an easy reach to pull down the switch and disconnect/reconnect the new switch. A little fussing to align the switch but when you hit the sweet spot it snaps up and in without much force. 10-15 minutes. A good video on panel removal on youtube: www.youtube.com/watch?v=AklfAVuhpx0

Thanks to all for the tips

Finally! Solved!

RacerTodd said:

I had the same issue on my Golf. Actuator started taking several tries to get it to pop, then finally nothing. I pulled the connector at the actuator, saw I had 12v when the switch was pressed and assumed the actuator was bad.
Picked up a used one, installed it and - nothing. Crap!
Checked the old and new actuators by giving them 12v directly from the battery, both worked.
Turned out, the switch was bad. I was seeing 12v at the actuator connector but that was with no load. The internals of the switch were likely badly corroded, meaning that it was unable to pass enough current under load to operate the actuator.
Simple to test. Pop the door panel off. Pull the connector off the fuel door switch.
There are four wires in the connector. Use a short length of wire to connect terminals 1 (RED/YELLOW) and 2 (BLUE/RED) together. The grey/blue and brown wires are for the light bulb - DO NOT mess with those, you could blow a fuse! Be careful!
If the actuator pops - you've got a bad switch.
Kicked myself for not doing a proper diagnosis the first time.
I was able to access the switch without pulling the whole door panel. I removed the three lower screws and upper Phillips screw. I then pried at the bottom until the panel popped out of the clips. Laid down on my back under the door and was able to reach up and access the connector to do the test.
Replacing the switch without pulling the panel can be done, but it's a hassle as you have to use a couple of small screwdrivers to release the tabs that hold the switch into the door panel.

Click to expand...

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Oh! I searched and read all the posts I found in the forum that came up. Didn't find the answer. Typed up all my trials and tribulations and searched again for a good place to post my issue. THEN this thread came up. My exact issues. Wish my search revealed this thread sooner. Thank you RacerTodd for your answer. I jumped the two contacts and my fuel door opened! I'll be buying a new switch for driver door panel and returning the actuator I didn't need. I guess a new connector doesn't hurt!
Thanks also to jcharing for your original post.

Both that switch and the rear hatch switch next to it bear the full current of their respective actuators, and over time the contacts arc up a bit.

If you have a can of DeOxit, a little spritz will rejuvenate your existing switch for another 100,000 miles.

Last year mine was a bit unhappy too. I can hear it trying to pull the gas lip open. I found that the mechanism is gummed up at the little catch so I lubed it and it worked again. Now it is misbehaving again. So I will see if I can get it working again just by cleaning and lubing it from the outside.