Repair / Refurbishment of seat heater / lumbar support

Does anyone have any experience with tackling the seat comfort elements - heater and lumber support?

The lumbar support on both driver and passenger seats is entirely non-functional (I hear the pump running but there is no actual change to the seat.) Also, the heater on the passenger side is intermittent. Are there suitable aftermarket parts available anywhere and has anyone tackled this issue themselves or is this really an upholstery shop job?

What is the model year?

Mine is an ‘88, so your mileage may vary. On mine, the drivers’ seat sensor failed for heater (which I just bypassed); passengers side had a broken wire where it connected to the element. Both repairs required removing the seat cushion upholstery.
The lumber support both had broken hoses to the bladder; I trimmed them shorter and dug the broken piece out of the receptacle. They leak slightly. A better action would be to replace the hoses. The lumber is accessible by removing the seat back rear panel, and could probably be done without seat removal.

Sorry I neglected to mention that… this is a '93 4.0 Convertible with the storage cubby in the rear, not the vestigial seats.
I’ve never tackled any upholstery issues before. Before I consider taking this on, does anyone have any suggestions / guidance? Any unusual tools I should consider getting or ‘tips & hints’ on how not to make a bigger problem for myself.
Honestly I can live without the lumbar and heater if I risk digging a deeper (and more expensive) hole for myself upholstery-wise.

You don’t need any special tools . Having Hog ring pliers would be nice…but you can manage without. I did my lumbar remove and replace without them. As pointed out, could most likely be a break in the hose between the motor and the bladder

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When working in the seat, there are lots of fun sharp metal edges. Your hand and knuckles will be in constant danger of scratches and scrapes.

To pull out just the bladder, its manageable with some pliers, possibly, but you might want some kind of hook pick set like this to help you hook the bladder back in:

If your seats are in bad shape, wouldn’t be the worst time to recover them. You’d definitely need the hogties then. Just make sure you have zipties on hand for the bladder job.

I’m not a mechanic and really don’t have a solution other than to share with you that I have a '95 4.0 convertible and had the same problem: inoperable lumbar support and heat functionality in both front seats. Luckily, I found an upholstery specialist nearby who could fix everything for around $800 (I think), and it was SO worth it. If you aren’t able to do it yourself in the end, I highly recommend you find someone who can because you will enjoy the result immensely.

Years ago, on my '88 XJS, I replace the dead heating elements with generic aftermarket replacements. Worked fine. But, you may have problems elsewhere in the circuit. There are relays and a timer…from vague memory. Also a vague memory of a tiny thermostat on the grid which can cause problems.

I repaired a leaky lumbar bladder on mine with with a bicycle tire patch kit.