Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

Since the keyless entry system stopped working last year, I've had to use the old-fashioned keyed locks, and number pad, to access my 1998 Mercury Grand Marquis.

Driver door and trunk locks work flawlessly, but the passenger door lock is uncooperative. It seems as if it only works when the temperature is somewhat warm - let's say, above 50°F. Which it is here only sometimes in the afternoon, this being winter in my area.

It goes like this: I'll insert the key, attempt to turn it...but, it doesn't. Maybe wiggles a little. That's it. I'm not going to force it, since I don't want to break the key off in the lock, and it probably still wouldn't turn.

At least part of the locking mechanism does function. I can unlock and lock the passenger door from either the driver's side number pad, or door-mounted lock/unlock switches (both driver and passenger side). It's only directly turning the lock with the key which doesn't work.

I've tried rattling the key in the lock. No good.

I've tried my extra key. No difference.

I've squirted some graphite lube in the keyhole. That helped when the lock stopped wanting to turn a couple of years ago. This time, it didn't help.

I'm reluctant to put anything else in the keyhole. Someone suggested WD-40, but that seems like a terrible idea, since it's not actually a lubricant. 3-in-1 or other oil could gunk up something sensitive.

Ours is a very dry climate, so I doubt anything is binding up due to rust anyway.

Short of taking this to a mechanic, any ideas?

How much of a project would it be to swap out the lock myself? Am I going to run into headaches due to the vehicle's notorious first-generation PATS?

It's weird that the *passenger* door lock has seemingly worn out, since it's the driver side lock that gets used most often.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

Jc Maxwell wrote:
> Since the keyless entry system stopped working last year, I've had to
> use the old-fashioned keyed locks, and number pad, to access my 1998
> Mercury Grand Marquis.
>
> Driver door and trunk locks work flawlessly, but the passenger door
> lock is uncooperative. It seems as if it only works when the
> temperature is somewhat warm - let's say, above 50°F. Which it is
> here only sometimes in the afternoon, this being winter in my area.
>
> It goes like this: I'll insert the key, attempt to turn it...but, it
> doesn't. Maybe wiggles a little. That's it. I'm not going to force
> it, since I don't want to break the key off in the lock, and it
> probably still wouldn't turn.
>
> At least part of the locking mechanism does function. I can unlock
> and lock the passenger door from either the driver's side number pad,
> or door-mounted lock/unlock switches (both driver and passenger
> side). It's only directly turning the lock with the key which
> doesn't work.
>
> I've tried rattling the key in the lock. No good.
>
> I've tried my extra key. No difference.
>
> I've squirted some graphite lube in the keyhole. That helped when
> the lock stopped wanting to turn a couple of years ago. This time,
> it didn't help.
>
> I'm reluctant to put anything else in the keyhole. Someone suggested
> WD-40, but that seems like a terrible idea, since it's not actually a
> lubricant. 3-in-1 or other oil could gunk up something sensitive.
>
> Ours is a very dry climate, so I doubt anything is binding up due to
> rust anyway.
>
> Short of taking this to a mechanic, any ideas?
>
> How much of a project would it be to swap out the lock myself? Am I
> going to run into headaches due to the vehicle's notorious
> first-generation PATS?
>
> It's weird that the *passenger* door lock has seemingly worn out,
> since it's the driver side lock that gets used most often.

Two possibilities,

Dirt/dust in the lock is mixed with the lube and causing it to gel and
bind when it's colder.

Because the lock wasn't used for a long time it has a small amount of
corrosion in between the cylinder and the plug (rotating part the key turns)

Either way -
Go get a can of brake cleaner, make sure it has the straw.
A can of compressed air - with a straw (or if you have a compressor a
small tipped blow gun)
and some graphite based lock lube.
Now use a bit of tape and tin foil to mask around and under the lock
(mainly to keep you from spraying the cleaner around and to protect the
paint during the next step).

Hold open the key door, stick the straw in as far as it will go.
Give it one short blast of cleaner.
Now insert your key and try to turn it. It probably won't turn very well
if at all.
Repeat the cleaner and key until the lock frees up. The cleaner will
spray through the tumblers and wash out the crud around the plug,
turning the key acts like a scraper and will break loose the crud so the
spray can work.

Now once you get it freed up. Hold the key door open and use the air to
blow through the lock and dry it.
Apply the lock lube into the plug and apply a quick shot of air to push
the lube out around the plug. Apply some more lube and repeat until the
lock works the way you want it to.

Don't use any type of liquid lube in the lock, it just gums them up and
causes problems.

--
Steve W.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

Or, just use the locks manually on it; something most
people forget is possible even on late models.

Personally, I miss crank up windows and pull-up-push
down locks. The best thing since sliced bread!

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

On Thursday, February 4, 2016 at 9:42:42 AM UTC-7, Steve W. wrote:
> wrote:
> > Or, just use the locks manually on it; something most
> > people forget is possible even on late models.
> >
> > Personally, I miss crank up windows and pull-up-push
> > down locks. The best thing since sliced bread!
>
> What he is saying is that the manual door lock doesn't work with the key
> either.
>
> --
> Steve W.

Precisely, it is the good old-fashioned manual way that doesn't work. I want to get in the car, I have to go to the driver's side & use the number pad or door switch.

I really miss the keyless entry. It was a great help when loading or unloading the car. I could be carrying something burdensome & not have to put it down to get the door open, unlock the door for someone else to get in, make sure I had locked the doors after parking, etc.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

point of clarification: By "keyless entry" I mean the remote control fob, which no longer works. The keypad on the driver's door still works fine.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

On Thu, 4 Feb 2016 12:22:09 -0800 (PST), Jc Maxwell
> wrote:

>point of clarification: By "keyless entry" I mean the remote control fob, which no longer works. The keypad on the driver's door still works fine.

You sure you don't just have a dead battery in the fob? Or maybe just
a bad fob? It could be a cheap fix.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

On Thursday, February 4, 2016 at 2:57:56 PM UTC-7, Bill Vanek wrote:
> On Thu, 4 Feb 2016 12:22:09 -0800 (PST), Jc Maxwell
> > wrote:
>
> >point of clarification: By "keyless entry" I mean the remote control fob, which no longer works. The keypad on the driver's door still works fine.
>
> You sure you don't just have a dead battery in the fob? Or maybe just
> a bad fob? It could be a cheap fix.

Yes to the first - replaced the battery, to no effect.

As for the second, if I can find a fob tester at a parts store, I can find out if the fob is dead despite having a good battery.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

On Thu, 4 Feb 2016 14:48:12 -0800 (PST), Jc Maxwell
> wrote:

>On Thursday, February 4, 2016 at 2:57:56 PM UTC-7, Bill Vanek wrote:
>> On Thu, 4 Feb 2016 12:22:09 -0800 (PST), Jc Maxwell
>> > wrote:
>>
>> >point of clarification: By "keyless entry" I mean the remote control fob, which no longer works. The keypad on the driver's door still works fine.
>>
>> You sure you don't just have a dead battery in the fob? Or maybe just
>> a bad fob? It could be a cheap fix.
>
>Yes to the first - replaced the battery, to no effect.

Did you program the fob after replacing the battery? It might be
necessary, even though it's not a new fob. It is necessary with new
ones.

>As for the second, if I can find a fob tester at a parts store, I can find out if the fob is dead despite having a good battery.

I think all the national chains have those for the customers to use.

Stuck passenger door lock (1998 Mercury Grand Marquis LS)
 

On Thursday, February 4, 2016 at 3:57:29 PM UTC-7, Bill Vanek wrote:
> On Thu, 4 Feb 2016 14:48:12 -0800 (PST), Jc Maxwell
> > wrote:
>
> >On Thursday, February 4, 2016 at 2:57:56 PM UTC-7, Bill Vanek wrote:
> >> On Thu, 4 Feb 2016 12:22:09 -0800 (PST), Jc Maxwell
> >> > wrote:
> >>
> >> >point of clarification: By "keyless entry" I mean the remote control fob, which no longer works. The keypad on the driver's door still works fine.
> >>
> >> You sure you don't just have a dead battery in the fob? Or maybe just
> >> a bad fob? It could be a cheap fix.
> >
> >Yes to the first - replaced the battery, to no effect.
>
> Did you program the fob after replacing the battery? It might be
> necessary, even though it's not a new fob. It is necessary with new
> ones.

Can't do it. My particular model year (1998) requires a trip to the dealer to pair new fobs or keys with the car. First-generation PATS wasn't that great.

I have previously replaced the battery in the fob. It didn't require any special procedure, it just worked.

To be clear: the fob stopped working before I tried replacing the battery, not after.

> >As for the second, if I can find a fob tester at a parts store, I can find out if the fob is dead despite having a good battery.
>
> I think all the national chains have those for the customers to use.

I'll have to pay Pep Boys et al a visit then.