Fear not the seat pot (potentiometer) How to rebuild one without removing it.

If the pot is broken that is not going to put it where it needs to be.

 

I think it also need to have SD1 to program. Do SD2 and SD3 not able to program these seat pots?

 

Of the 3 only SD1. And those are getting rare even in the dealers.

 

The seat position potentiometer/gear box is the same component used in mid 90's Jaguar sedans. I have a 1996 XJ12 that experienced failure of the drive coupling as described. here. I opened it up, modeled the coupling and 3D printed replacements from ABS plastic. It's a bit stronger than the original nylon, using a .005" resolution and modifying the print configuration for increased density makes a pretty good part. The original spring clip can be reused or a small o-ring will work as well to hold the petals against the ball on the gearbox output. The original ones I made were a bit rough (I hadn't refined the printing) but they've been in service for 3-4 years with out problems so far.

If there is interest I'll figure a way to make them available for about $7.50 each. I sent some to a guy in Australia with a 355 the other day to try out. He already had someone else who wanted some but I have yet to come up with a way to sell them. I may put them for sale on eBay to see how that works. That may be the easiest.

 

Good luck with the sales, Niles. As you have discovered, unlike the Jaguar potentiometer, the F355 potentiometer is a vital part of roof operation. Your 3D printed sockets will take away some of the "terror" of not being able to find a fix for our roof problems

 

Really great that you have achieved this.

Thanks Qavion for adding this link to my roof repair thread. Nileseh, if you put these up for sale on ebay or somewhere, let me know the link and i'll add it on my Spider roof repair YouTube video.

 

I fixed my mine by installing a roll pin through the sphere as shown on this site, but if you are going to offer new improved ones, I'd be interested.

 

Does the roll pin method allow slip at the potentiometer end stops? I think the idea behind the "limited slip" ball and socket is to stop the potentiometer breaking if the seat moves too far in a particular direction.

 

I can't see how it would allow any "slippage", but I have not yet had any problems and I did that fix 3 yrs ago.

 

Looks like Niles has finally released his 3D printed seat potentiometer repair kit on eBay.

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

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It even comes with an assembly tool to prevent damage during installation and a new spring clip. An assembly guide is shown on the eBay page.

Not so expensive considering the effort which has been put into this project.

 

Has anyone detailed how to remove the seats and the actual process i,e what position to have the seat in before you remove it (if that matters) and how to actually meter out the new pot to ensure its at the right value?

I am struggling to understand how you set it up. I get that you need to see a certain resistance but how do you actually go about doing that? Do you do this with the seat off its track? Do you measure the value at a known point before you remove the seat and then ensure the pot is at that known value before it goes back on?

The whole system looks to be kind of locked so I dont want to damage an expensive part as surely the pot will have an end point in its travel?

 

The good thing about the unmodified potentiometer is that it doesn't break when the seat hits the endstops (no matter where you position the potentiometer). The ball and socket "clutch" slips.... except if you glue it or nail it together as shown in some message threads. That 3D printed part in the photo is a replacement socket. The bad thing about the potentiometer, is that, after a while, it slips too much (not only at the endstops) and the roof ECU doesn't know where the seat is (and the ECU either stops the seat prematurely or doesn't stop it before it hits the endstops). Unfortunately, the Roof ECU is not self-learning. It has to be taught (with the use of the Ferrari SD1 tool). The best do-it-yourselfers can do, is use the existing calibration in the ECU memory (set up at the factory or by a Ferrari tech after that).

 

Thanks the question is if you DIY then how do you ensure its at the same value? As I see it the pot is driven off a shaft which is driven by the motor. Once thats assembled surely there is no way of adjusting the pot?

 

I'm hoping someone will chime in here, as I haven't actually done the job myself, but you should be able to change the position of the potentiometer with it fitted (because of the ball and socket slip). I'm pretty sure you will need to open up the potentiometer case to do this. I'm thinking it would be next to impossible to do the case opening and adjusting with the seat fitted to the car. I can barely fit my hand under the seat.

Have you actually sourced a new pot or are you going with the repair kit? If we know which, the experts can guide you down the correct path as the procedure steps may vary a little.

Prior to removing the seat, I would position it to give you the best access to the front and rear track mounting bolts. The track with its endstops comes out with the seat, so you can do your adjusting with the seat removed. You can always change the position of the seat after it has been removed from the car by applying 12 volts to the motor directly.

There are a few forum posts which give typical potentiometer resistance ranges (from one endstop to the other). I've written my values down somewhere. You could get yours from your good seat. You could run the seat you are working on to one of the endstops and set up the new potentiometer to a typical value (either before the installation of the potentiometer or after). The potentiometer resistance range when not fitted to the seat is perhaps less relevant, but it is known (for extra confidence).

Prior to removing the seat, be sure to protect all the surfaces (paint and leather) to prevent damage.

 

Here's one of my wiring diagrams which may help:

https://www.dropbox.com/t/gt5wSUrUYyIKAEhx

Link expires in 6 days.

Note that I haven't shown (in detail) the wire colours for the short section of wiring attached to seat potentiometers as they can vary. You may want to compare the colours prior to fitting a new potentiometer to make sure you are checking the resistances of the same wire pairs.

 

Cheers for that I have a copy of that will take a good look.

Qavion its a new pot, well I hope - its off a jag so wont know for sure until I get the seat out and try it.

I have seen the pot values off another thread for max and min. I guess the only way to find out is to get the seat out and have a go.

I assume there is nothing I can damage? Kill the power and the seat only looks to be held in with 4 bolts. 2 wires to unclip 1 for the pot and 1 for the motor?

 

The pot I have ordered has white, white red and white black wires.

So I assume its
white = Brown
white red = Yellow
white black = Pink

As best as I can tell the housing and drive socket looks identical to the ferrari one.

 

I can't remember if the mounts and plug are the same as the Jaguar's, but some or most of the internals should be the same. I thought the Jag pots were just as rare. The 3D printer, Niles, was from a Jaguar forum.

On the passenger seat, there should also be an orange and a black wire going to a jumper. On the driver's seat is another jumper, but with two orange wires. These are attached to the seat frame and disable the roof (I recall) if they are disconnected. On the driver's seat, there is also the seatbelt warning wiring.

 

What part number did you use for the seat pot from a Jag? Inquiring minds.... I am tired of rebuilding mine.

 

Some part number details here for the Jaguar XK8 (X308) seats, but I can't remember which seat axis corresponds to the Ferrari pot:

https://www.jaguarforums.com/forum/xj-xj8-xjr-x308-27/repair-memory-seat-potentiometers-131192/

I've made searches for the Jag potentiometers many times and haven't found a new one.

 

Used Jag pot on eBay without plug:

https://www.ebay.co.uk/itm/223737651974?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338722076&toolid=10001

 

Amazing... found four new "Ferrari" pots...

https://www.ebay.co.uk/itm/144052195866?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338722076&toolid=10001

Only 279.00 Euro (U$341) .. and no plug... so probably old Jaguar stock (still amazing).

 

I think its JLM21119.

Second hand one £50, new one £100. We will see what turns up!

 

Actually, I'm starting to think that someone realised how much they could charge for a plastic part with $2 worth of electronics inside and started remanufacturing them in China. Seems similar to what happened with the HVAC fresh air flap motor-actuator. They were getting harder and harder to find then lots of them started appearing.

I bought a EEPROM/Bios chip reader a few days ago for a few dollars and it was a hundred times more complex electrically.

 

The Jaguar Kit "GNA 4711" contains nice parts for us F355 spider seat potentiometer victims.

a) the motor can be obviously used for our seats (only the plug must be changed).
b) the included seat potentiometer has at least the same housing (incl. the rubbish slip clutch). Even the potentiometer values are quite close to the original. Maybe by changing the plug it may work 1:1 but I did not test it.

If you are lucky this kit can be sourced for "small money". I bought new 4 kits in UK for around 30,- EUR per kit to be stocked as "a last parts reserve" since I only have 2 original Ferraris ones left.
Some pics of the kit present a good view on the potentiometer and you can see that it looks the same as the Ferrari part.

The kit is at least a good resource even if only the motor and some potentiometer parts can be used. Better than nothing.

Regards, Thomas