456 seatback activator

Hello,

my passenger side seat back won’t tilt forward and the seat slide forward doesn’t activate when I pull the handle. There is click but then nothing.

is this a common issue and does anyone know the fix?

 

Many many years ago I had a similar problem. I had just purchased the car so brought it back to the dealer. Turns out there is a fuse under the seat (somewhere) which was replaced and fixed the problem.

 

456 or 456M? I don't know if the cars are similar, but there are a number of fuses, microswitches and a potentiometer in the 456M recline system. Is the seat otherwise behaving normally with the manual controls?

 

95 gt. Yes the manual controls work normally

 

Maybe @rviani can remember if his normal seat controls were working or not? It seems odd to me that the normal controls should work (with the power available), but not the easy entry system.

If the fuses are ok, that just leaves the hard bits to diagnose. Unfortunately, we don't have any wiring diagrams for the 456GT and (just now) looking at the parts catalogue, there seems to be lots of different components and part numbers.

Potentiometers and switches do fail. Potentiometers are no longer available (or are stupidly expensive if you can find them), but you may be able to get a repair kit for them on eBay. The potentiometer internals are the same as the potentiometers internals on F355 Spider seats.

https://www.ebay.com/itm/143665671697

Hopefully the ECU isn't faulty. The left and right seat ECUs are interchangeable if you need to figure out that.

All I can suggest is removing the seat/s and checking the individual components or... leave it to the expert$

 

My recollection is that the seat (fortunately passenger side) was a complete "dead duck"

 

Perhaps in this case, a power/fuse issue? I've been told there are fuses under the seats, but haven't seen any photos of them.

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On the 456M and 550, the fuses are in the passenger footwell, separate to the main relay/fuse panel (although I don't know if there are additional fuses under the seat). Does the Owners Handbook offer any clues?

 

The 456 has a potentiometer on the seat back recline on a splined shaft driven by the gears, just like on the seat forward and backward travel. It’s exactly same unit, and they are very fragile. Usually they break either fully fed or fully back, meaning seat is undriveable stste. As lots of previous posts circa 2015, you can source a jaguar potentiometer, it’s same, just different wire colours. Mine did this few weeks ago, connecting the potentiometer works, I’ve tried it loose , just connecting wires it without fitting it properly. The problem i have is how do you take the seat apart to remove splined shaft to slide of the old sensor and refit new potentiometer? I can see the shaft and see the sensor after removing the seat belt reel. It may be straightforward in removing seat bolts, removing bits of covers, but it isn’t simplest task trying to do it in single garage and manoeuvring the seat around. Help appreciated.

 

take the seat out and examine it and see if you can find the potentiometer and/or microswitch. see if you can fix them yourself. also clean out the motors - I'm sure they're gunked up. Let us know how it goes. I'm about to do the same with my '95...
good luck!

 

Thanks.
I located the re one seat potentiometer just below the seat belt harness at lower back seat. The problem is how to remove it of the splined shaft that the motor drives. I know it’s the potentiometer, as when I disconnect it on the molex connector and connect the replacement jaguar part I can then move seat back recline and fwd using the seat adjust buttons on the side of the seat which I could not do before. But to properly replace it I need to slide the old switch off the splined shaft that goes across the seat back from the gear drive on one side the seat to the other, and slide the new one on? The splined turns the potentiometer cog which in turn changes the resistance on the potentiometer. The problem with the broken one is it breaks at end of travel either fully fwd or fully back and then the seat ecu will only allow the opposite end of travel, as as the cog no longer turns the potentiometer and so doesn’t alter the resistance, the ecu then thinks the seat is at end of travel.

 

I don't know if it's possible on the 456, but on the F355, the seat potentiometer internals can be repaired without removing it entirely from the shaft.

https://www.ferrarichat.com/forum/threads/fear-not-the-seat-pot-potentiometer-how-to-rebuild-one-without-removing-it.288373/

I'm not sure if it can be done without removing the seat though.

The repair kit was available on eBay, but may be out of stock.

https://www.ebay.com.au/itm/Ferrari-355-seat-position-potentiometer-drive-repair-kit/143665671697?

Maybe you could try contacting Niles, the seller.

 

I just took out my pass seat and will be fiddling for the next few days/weeks/foreseeable future! Again i’m trying to fix the easy entry/ auto forward/back thing; otherwise the seat works as intended with the side elec controls. HOWEVER there has been some…manipulating of the electrics cuz there are some splices and taping etc under the seat….
Pics and updates to follow

 

I believe that SOME of the related parts were also used in Jaguars of the same era. Is that true?

 

The body of the potentiometer was the same, but Jaguar potentiometers are now just as expensive/rare. The creator of the repair kit on eBay was a Jaguar owner.

 

so real quick before I head back there this afternoon – if all three of the micro sensors work, and all of the electronic controls work as intended, but the easy entry does not go forward or backward does that point directly to the potentiometer? Also, as I said, I’ll need to dissect some of the wiring without disrupting any of it per se. I’ll take pictures and see if we can make sense of it. Even though I tested the micro sensors and found them to work, it could be that the ends of the wires are not even hooked up. Will follow….

 

Ok so here are some pics (pass seat only). I have some questions….and some ideas of what might be what. Opinions appreciated please!
The splices are concerning (in the second pic)

also can anyone clarify before i remove something i’ll never be able to replace: to remove the seatback you remove the 2 lower screws and lift up BUT you also have to remove the seat back lever. So you remove 2 small screws to get the handle off, but there’s still a little part sticking out that needs to be removed. Is it as simple as removing the center hinge pin on the springed lever? It feels like it’s under attention and if I remove that pin, I’ll never get it back in! See pic 3

ty in advance
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What happened to your old pot casing? The plugs have 3 wires, not two.

The "unsure what this goes to" plug is probably the pot plug.

(EDIT: ...or at least one of the potentiometer plugs. On the 456M, all the motors have power wires and an associated internal potentiometer)

 

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So on the 456 (non-M), the pot is on the fore/aft drive. I wrongly assumed it was like the M car with the potentiometer on back tilt.

 

456 Potentiometer

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Huh you’re correct I think, based on your pic of the Pot. I could swear on my other seat that 2-wire connector was connected to the Pot; I’ll double check in am and take a pic.
No clue what happened to the rest of it!

yes there are 2 Pots per seat on the fore/aft- #13 in the pic, and the other I believe is unlabeled part just behind the number 12

 

Two pots per seat for the same axis... Crazy. I was thinking that the two drive motors were in series, so should have the same position.

 

so help me out with something.....
If the Pots control easy entry fore/aft then how do they work? if they are on the rotating shaft which doesn't move until you activate the motor...
I guess i'm not entirely sure how potentiometers work...

In any case I think I figured out why my pass seat doesn't easy entry fore or aft - because i'm missing both Pots
however on my drivers seat it DOES easy entry aft, but not fore - and that may because I DO have one Pot....

conundrum...

 

and you were confirmed correct (by looking on the driver side) - I wrongly labeled the wire connectors. The 3 wire connector is for the Pot, and the 2 wire one (that I wrongly labeled as for the Pot) is actually for the seat belt receptacle - presumably for the light on the dash? (seat belt buckled or not) or to alert the airbag system that someone is sitting there; since my car does not have airbags (removed) someone may have wisely removed/disable the wire to the seat belt????

the only thing that has me wondering is on my pass seat where I have no Pots there is only 1 3 wire connector hanging out; and on my driver seat where I at least have 1 Pot there are no other 3 wire connectors to be found???
so more confusion.... and more digging....

 

It's just a position feedback system. In general, pots tell the ECU where the seat is, either for the purposes of memory buttons or for (apparently) easy entry. One wire will be earth, one will be power and one wire (middle one) is the position feedback.

Here's a thread on the 355 forum with some potentiometer resistance values. I'm not sure if the gearboxes on the driveshafts are the same (item 12 in the diagram above):

https://www.ferrarichat.com/forum/posts/136345643/

Indeed. I don't know where you can go from here. Fixing/finding one pot is enough, but 3??? If you do buy a second hand one, you may be able to use the eBay kit to fix it if it's broken.

Ferrari has this aversion to including seat belt wiring in their diagrams, so I’m not sure what the 2 wire passenger plug is. The "passenger presence" detectors I'm familiar with have 3 wires. but they're on more modern cars (F430). The brown and yellow wire colouring is no clue. Does your Owner's Handbook mention "Driver's Seat Belt" Warning in the Controls and Instruments section? The WSM I have doesn't even show a seat belt warning light.

 

Unless the wiring for this has been chopped off, perhaps the parts manual is wrong and there should only be one pot on each seat (as per @AMIRL 's comment: https://www.ferrarichat.com/forum/posts/149470279/ )