456 seat operation

what exactly is you seat problem?...seat not reclining, going fwd, or the rear seat button not working...

Seat electronics on 456 are noted...I have a current issue on the upper rear-entry switch not working....but plan to 'tear it down' soon to fix.

 

I had the reclining problem as well. The main dealer changed something worth good 100 Euros or so, I recall a potentiometer which fixed the reclining problem but left me out the automatic return to its original position which I can easily live without.
I can check the old bills to find the part number if you wish to explore this route.

 

Every now and then, my drivers seat goes all the way back when I close my door, and refuses to go forward. When I push the relevant switch, it only goes forward a few mm. So I have to push the switch a hundred times to get my seat in the right position.
When I disconnect/reconnect the main plug under my chair going to the seat's ECU, I can hear a peep, and after having done this, everything is O.K. again.
It is a bit frustrating, but so far I can live with it.

 

I had same problem with both my seats , luckily for me i spotted the problem before i bought the car so it was fixed beforehand, that turned out to be the potentiometer

 

What exactly are the symptoms when the potentiometer is malfunctioning ?

 

wow..

I just all of the sudden had the same probelm. BOTH SEATS!!!!

Seats do not want to move back and forth! It reclines, though...

I should try that coupler reconnection thing. This is amazing.. both at once..

 

What is supposed to happen is that when you release the seat upright to gain access to the rear seats the entire seat moves forward to give more room for passengers to get in the back, once in, and the seat upright is returned to it's original position, then the entire seat moves back to it's original position. The potentiometer controls these functions, hope this helps.

 

If the seat operation restarts after disconnecting and reconnecting the seat e.c.u it's the pontentiometer at fault. When they begin to die you get a big internal resistance build up, and the e.c.u can't see the signal properly. They aren't to bad a job with a bit of patience and care, just watch your back when removing the seat from the car, they weigh as much as a 4 bedroom house!

 

No they are different. The control unit is a big box, with a large amount of wiring feeding into it. This is the brains of the outfit, it controls the switching of all the various motors in the seat, as well as storing your seat memories. The pontentiometer is a sensor, which monitors the position of the inards of the seat and sends this message to the control unit. It does this so that the control unit knows which position the seat is in, to base it's movement calculations on. If you reach underneath and disconnect and reconnect the seat control unit, and everything starts working, then it's a pontentiometer fault. If you feel confident in striping the seat down to do the job yourself, then go for it and save yourself some money, but if not, i would pay someone else to do it; it's quite easy to damage the leather if your not careful. Good luck!

 

That's cool. Yeah, when my seat died, I totally felt the build up.

I will take the seat out and see!

Thank you so much for such perfect diagnosys.

 

The automatic return may have stopped working due to a different problem. There is a switch on the seat back catches which tells the control unit that the back is locked into position, so it can start it's journey to it's original position.This may have been disturbed when they stripped the seat to do your pontentiometer, they are very prone to this. Remove the covers at the base of the seat back (the small ones), and you will see a microswitch inside. Check this fully engages with a 'click' when the seat back is locked into position. You can adjust it by gently bending the arm of the switch with a small screwdriver.

 

My automatic return only works on the driver's seat, and honestly I think I prefer it that way. With my son in the passenger side rear seat, he likes the front seat most of the way forward anyway, so it saves me having to hassle with it.

 

I found that the seats are quite sensitive to being jammed by things. My passenger seat wouldn't go right back and it turned out that there was a map on the floor stopping it. I also noticed this when I put some new mats in that were slightly too big.

In my Merc the seat will just crush whatever is in it's way!

 

Does anyone have the schematic for the 456 seat ECU and/or a wiring diagram for the seat? I am also having problems with mine. The passenger seat is completely dead. Everything on the driver's seat works except the switch to incline the seat back.

 

I have a similar problem with my passenger seat. When I lift the back to let it go forwards it does nothing, it also doesn't go backwards automaticly. But all functions work very good except this function.

I will take some pictures.

Kinnie

 

Check all your fuses are intact, then switch the e.c.u's side to side. I will look tomorrow for the schematics and post up if i have time...

 

Tried to get one of the seats to work properly for the rear-entry switch.

Noted all the above comments.
1. remove the 'wrap' around with the side control swtiches which is quite easy.
2. remove the beauty caps on rear seat-back near bottom and remove the two screws that hold the seat back bottom in place
nothing will be much gained by this.
3. remove the seat belt bolt 17mm [if I remember] and then using a small allen wrench, undo the same leather cap that houses where that belt was bolted. [have taken numerous pics, but not ready to post them yet]
4. undo the allen bold holding the rear seat motor cap which is just rear of #3 and below the seat back near the door.

The allen bolts are buggers to get into. UNLESS you use a mirror like I did: went easy after that.

You will notice a lever switch [again, I have the pic, will post later] that is triggered by the upper handle on the seat top, back.
The top 'switch' is nothing more than a sort of bicycle like lever that pulls a cord, that rotates a cam against the lever switch.
The switch is the key. Seems easy to replace from anyone.

Tracing out the wires from that lever switch to the control unit was a bear, but it is wrapped about the bottom, back rod via zip ties.
When I ran my hand under the rear back and found the wire, it sort of made a 'beeping' sound. Hmmmm, could this be a short?

unplugging the control unit under the seat [easy to get to BTW, just undo the seat bottom straps] did nothing for my top seat control unit problem.

TIME: about 50min.
TOOLS : pair of pliers, two diff. allen wrenches VERY small ones, like 1/16/18 inch [mm?], screw driver [ratchet is best], 17mm stubbie, mirror, and a parts container to keep it all

I took off the lever switch to check it out, via a small allen wrench and noted the part numbers etc. and felt it was in order. Tried to get a continuity test, but couldn't find MMeter or even desire to make up a light bulb tester, so just ran a wire across the connectors to see if that did anything and of coures: NOT.

My seats go fwd back fine, it's the top rear entry that's the problems. will keep informed.

 

In the FWIW department....... I've had excellent results when dealing with connections/pots...etc where they just get coated over time due to lack of use, using the Deoxit products. You can get the small (2) pack at any RadioShack where they have the Deoxit-5, and then the protective coating. AMAZING STUFF. Spray it on, work the part/switch........ then spray on the gold can protectant.

As-long-as you have some small opening (very small) to spray in/onto. (They provide super small straws)

 

thanks, not sure that is the problem with my prev. post, but enjoy this hint.

 

Any solutions to this problem?

I will be visiting a friend today who also has a problem with his seats, as well as headlights going out due to fuses.

Thanks

 

This is correct, but only for the driver's seat.
The passenger seat is supposed to go forward automatically, but not to return back on its own.

 

I bought an original Ferrari OEM ECU for $900 (about half the dealer price) from Specialized Italian Recycling (.com) in Sacramento, California. The dealer's mechanic mentioned that the Jaguar potentiometer is the same as that used in Ferrari's and costs less than $100. Fortunately, I didn't need to replace the potentiometer so I don't know the part number.