Loud Buzz from Lifgtate actuator when locking

[NOLATahoe2020]

The rear liftgate of my 2006 Tahoe 5.3L Z71 150k miles was not locking or unlocking. There was no click noise when locking or unlocking. The problem was intermittent. So I decided to change the actuator. A few days before the new actuator arrived, the rear actuator started working but made a terribly loud buzzing noise when locking. It did not make a noise when unlocking.

So I changed the actuator and everything worked fine for a day. Then the new actuator starting making that same terrible noise. the new actuator has been installed for two weeks now and every time it locks it makes that very loud buzz. The buzz sounds longer than it takes the actuator to move to the locked position. It's as if the motor is running longer than it needs to move to the locked position and is stripping the gears inside. I suspect that this is exactly what is happening because I disassembled the "non-working" actuator and notice that the plastic gear was somewhat stripped in the place where the metal motor's driving gear touched the plastic.

I changed the relays in the interior fuse box but that had no affect.

 

[PNWYukon]

You could test your actuator harness for voltage spikes or irregular voltage.



Looks like at least one relay you could look at.

Do a voltage test at the fuse to look for anomalous voltage while operating the actuator.

 

[NOLATahoe2020]

You could test your actuator harness for voltage spikes or irregular voltage.

The voltmeter registered 12v max.

Looks like at least one relay you could look at.

Tried one relay. Could there be another?

Do a voltage test at the fuse to look for anomalous voltage while operating the actuator.

I will do this. But wouldn't I see that at the actuator harness?

Another test I did was to reverse the polarity of the actuator which showed the UNLOCK making the loud buzz. This means it is not the actuator. Whatever is sending the LOCK voltage is causing the issue.

 

[Doubeleive]

put in a new oem one and you probably will never have another issue with it. if the gear is stripped it's going to make noise no magical electrical gremlin will cause that.

 

[NOLATahoe2020]

put in a new oem one and you probably will never have another issue with it. if the gear is stripped it's going to make noise no magical electrical gremlin will cause that.

I am happy to stump for the extra cost, but I don't think the actuator is the issue, because I reversed the polarity coming into the actuator and the noise happens with the UNLOCK. If I switch it back to normal polarity the noise happens with LOCK function.

I checked the voltage at the ECC/TPM fuse in the cab (which handles the liftgate LOCK but not the UNLOCK) it reads about 12V when not is use.

 

[Doubeleive]

I would just replace it even if it is a used one from the junkyard, if you then still have a issue then proceed with more troubleshooting, if you replaced it with a cheapo aftermarket actuator and it worked for a day and then started making noise then that's the most likely issue. 2nd option take it back to wherever you bought it and swap it out for another one.

 

[PNWYukon]

If you are in there, can you move the lock/unlock by hand? I had this problem with a different rig not locking the lift gate and it turned out to not be the actuator, but the metal mechanism that the actuator tries to move. It was seized from being greasless over the years. I could not even lock it with the key. Had to take out the whole mechanism by disconnecting the locking cables, handle rod and key rod. Did some brushing, scraping and filing and greased it up and now it is like butter.

These older mechanisms can dry out and get to metal on metal and stick or seize. Just a thought.