Hey everyone,

Had a gremlin since I bought this 2000 Coupe, 6MT in 2017. The passenger door will lock with all methods (driver door switch, passenger door switch, FOB) but will only intermittently (less than 1 in 20 times) unlock the door.

Unfortunately I committed the sin of parts chasing and have already replaced the lock actuator, entire lock assembly (with another new actuator), and have now bought a 2nd hand passenger door module.

The results:
The 2nd hand module unlocks the passenger door, but does not lock it. It does not matter the combo of original vs. 2nd hand module, new actuator, entire new lock assembly with actuator, the passenger door either locks but won't unlock, or unlocks but won't lock.

I have put a voltmeter to the 2-prong connection to the actuator and both door modules supply ~+10 V / -10V depending on lock / unlock. My battery was a little low on the voltage during this last check, around 12.05V. 10V was all that was seen at the actuator, though my harbor freight free multimeter isn't exactly a marvel of engineering.

What am I missing? Is there some security feature I am unaware of? How can the prong be seeing the correct opposite voltage for lock / unlock on two different lock units and three different actuators and produce a mirrored fault between two door modules?

Thank you for reading through my saga,

-Brian

 

your original problem with that door was likely the relays in the passenger door module... Your "new" i.e. used door module likely ALREADY had a bad relay...

You can buy the relay's for like $1.70 a piece, de-solder the old ones and re-solder the new ones.

You can also send your door module to a place that will fix it for $50 and send it back... I bought a $25 soldering iron a $5 roll of desoldering wick and 4 relays for $18(4 relays plus shipping) from Digikey... and knocked out both of mine.

One relay is for lock and one for unlock.

The drivers door on my car didnt do anything when I bought the car. Replaced the two relays a few weeks ago and back in business.

 

Thank you!

I was thinking that would be the next step...I'm not a great solderer so I'm a bit worried about what is involved. Watched a few videos on it so I think I know what needs to be done, just very unsure at how well I'll manage lol

It blows my mind that the voltage reads correct at the actuator but still has a bad relay. I think this is why I avoid most electrical issues...

Thanks again!

-Brian

 

I did zero electrical trouble shooting with mine so I cant comment on that... There were enough reports of the symptoms matching that I just dove in with the relay replacement.

I hadn't soldered anything in 10 years at least. Just bought the 40w pencil soldering iron at home depot. I had to order the desoldering wick from Amazon. Had I realized I needed the desoldering wick I would have ordered it from digikey with my relays.

There is a thread somewhere with the step by step, but basically when you open the module there are 3 relays all lined up on the side. Its the bottom and middle relay that need to be de-soldered and replaced. Was really easy once I got the hang of using the desoldering wick.

 

Did you have to cut away the "resin" coating that covers the board?

One of the videos I watched the guy had a lot of trouble with the solder wick.

 

Once I had the pins desoldered I just pried gently on the relay and they broke free from the resin... I took a razor blade and very gently cleaned the board a little under the relay.

the desoldering wick definitely took a little bit to figure out. ALWAYS cut it so you have a fresh piece on the end. I also noticed if you try to spread the fibers out just slightly it worked better also. If you attempt to use it and melt the flux, but dont pull solder, that piece is crap, cut it and try again. I also found that if I heated and melted the solder by itself first, then went back at it with the de-soldering wick, it worked a lot better. And on one or two connectionos, I actually had to ADD solder, then go after the whole mess with the desoldering wick to suck all the solder back out. Like I said, took me, probably the first relay(5 pins), to figure out how to use it correctly and the next 3 relays were done in like 10 total minutes.

 

Thank you very much for the tips, going to order from Digikey and try and get a decent soldering pen.

There are a MILLION soldering wick options...did you have a preference for the one you chose?

 

Thats what I ordered. Let me look on digikey and see what all they have. I think the smaller the better and I think the 2mm was the smallest I could find.

ETA: digikey has that same brand... MG Chemicals. I bought the 425-NS. They have a 424-NS which is .050 wide vs. .075 wide that I bought. I THINK the narrower would be better.

 

Digikey can go all the way down to 0.025"...that seems maybe too small??

 

This video shows howto replace these door relays