Sudesh

I bought a facelift model, 2003 Mercedes CL500, the central locking will not work via the remotes if the car has been left over night, or parked up for a few hours; so I have to open with the manual pull out key.

Once I start the car and drive it for 15mins, the remote central locking works fine again, and will stay working for a few hours.

I replaced the batteries in both remotes, which did not help, I put a new battery in the car, which didn't help either, I replaced the RF antenna/amp in the headlining at the rear, tried the key close to the door handles, no change;
checked the locking unit on passenger side behind the boot lining, all the tubes are intact and the wiring and plugs are like new. As I had the car out today, the remote locking is working and I could hear the ECU triggering just fine too.

Sent the car to the Mercedes specialist I use here, Got the car back after being checked on STAR, the guys said nothing is showing up or indicating there is a issue, they checked the locking on star with both keys I have, and all checked ok. They are now stumped and have sent the info and fault to Mercedes, haven't heard anything back yet.



So wondering if anyone has any other suggestions?

benzmodz

What happens if you point the key at the infra-red window in the door handle ?

Sudesh

Hi,

Already tried that, doesn't work either.

Patrick Yap

I have a C200 that has similar issues. The central locking seems to work later in the day. So I have to use the manual key to open the door.

The batteries of both keys are working. The central locking is working.

Is it the sensor?

Fayde

Do the locks open and close with the inside manual button? Does the trunk lock/unlock with FOB?

Sudesh

Trunk works fine, I was told it is on a different receiver or something.

The locks work fine with the dash button.

Patrick Yap

Yes, the locks open and close with the inside manual button.
And trunk locks/unlocks with FOB.

Fayde

I know the PSE pump will shutdown separate legs of the system (i.e. "just" locks) if it detects what it thinks is a pneumatic leak in that leg so the rest of the system (like trunk) can keep working. You might want to remove the fuse for it for about an hour then plug it back in and try the locks immediately. If they work for a while.. then stop working again, you may have a leak in that leg. Search for "PSE fuse" for fuse identification and location for your year model. I believe it is under the passenger side rear seat, 4th or 5th from top right of block.. but you should really check.

Sudesh

Hi,

Thanks for the reply. I'll run that test now.

On the fuse diagram that comes with the car, I didn't see anything saying PSE, but there is a fuse related to CENTRAL LOCKING, F62 on the diagram. Then there are fuses in the same are related to POWER LOCKING

I've pulled the F62 one as it's the 4th or 5th from the top right.

Sudesh

So I tried the test, pulled fuse F62, left the car for over an hour, put the fuse back in, Central Locking is working right away. Tried lock/unlock a few times and the system worked perfect.

Sudesh

So just to be sure, I tried the fuse test twice more. This time after putting the fuse back in from leaving the car for over an hour, the locking was still the same, wouldn't work like before.

Fayde

little confused.. did the locks work the way they should after pulling/replacing the fuse? Did they work for a while correctly and then started to malfunction again? Or never worked correctly after pulling and replacing the fuse?

If they worked for a while after pulling/replacing the fuse.. then stopped working again.. Your PSE pump is going out. You "may" also have a small pneumatic leak in the lock/unlocking leg. The pumps are around $150 used and I have seen new ones for ~$400. It is an easy DIY project.

Sudesh

Hi,

No the locks didn't work when I did the test 2 more times. I even have the fuse pulled at the moment, to give it one more test in about 30 mins.

awiner

Pulling the fuse immediately resets the PSE. No need to leave it out for a long period of time for a reset.

Sudesh

I've tried it a few times now, no affect.

What I dont understand is, why the system works ok after driving the car for say 25mins or so.

biker349

check the state of your battery.

Sudesh

Hi,

As mentioned in my first post, Battery is brand new.

Fayde

Well, have to go back to basic electronic theory here. It seems that after the circuit "warms up", everything works. Could be a floating ground/short in the controller/motherboard. Only way to test is to replace the unit and see if the problem goes away. Have you tried completely disconnecting the unit then re-connecting to make sure there isn't a capacitive charge building at connectors?
If the infrared doesn't work also then it isn't the RF receiver. Does the trunk or alarm functions work when the locks are not? If they do, it could be a controller motherboard issue.

Sudesh

Hi,

The RF receiver in the roof was replaced with another, this made no change.

The trunk works fine, but I have been told it's operated differently from the doors?

The alarm on the car works, every morning I have to open the car with the manual key, as soon as I open the door the alarm sounds.

When you refer to the "unit" which unit is it? The one in the trunk behind the left panel?

Fayde

Sorry, was out of the country on a project. Did you find the problem?

bmw_1985

Sudesh, I have the same problem as you, after driving the car the remote locking works for 10mins or so then nothing at all on the key fob. However mine does work every time for about 5 seconds after I have removed my key from the ignition, then it goes off again at the same time as my instrument cluster goes off. The trunk release on the two keys ive got has never worked. I have spoken to someone in Birmingham UK who specialises in just Mercedes Key replacements and he said he is 95% certain that its the EIS ignition switch that is failing and will eventually lead to failure to start the car. He advised taking it to Merc at a cost of circa £800-100. So I'm trying to figure out if his 5% doubt can be found elsewhere.... Keep us posted

RBT252

Did you ever get to the bottom of this?