Question about aftermarket seat heaters

[Rotor Head]

Hi All,
Replacing my Recaro comfort seats on my '73T, 'cuz they need it. Has anyone ever decided to eliminate the 50 y/o heating system and heat exchangers? Figure I'll use aftermarket electric seat heater pads when they cover the new seats and buy headers eliminating the exchangers. I live in California so there is not much cold driving to worry about. Any ideas or concerns?

Thanks, I appreciate your thoughts.

[OldSpool87]

Folks swap to headers without heater boxes/exchangers all the time . If everything is working, why not just keep the heat off?

[Rotor Head]

Thanks....
The heat is not working well either.... (The seats are old and they need an update).

[Winter]

Following.

I have considered this as well (just the heated seat part) and will probably add that functionality when I recover my seats.

I feel that making sure the electrical system has been fully sorted will be important for this mod, and upgrading to spade fuses and appropriate relays should be done prior or in tandem with adding heated seats.

Hopefully someone who has done this will chime in.

[blucille]

I’ve added seat heaters to a few old 911’s. My 72 and 79 currently in the stable.

Living in the northeast, I feel it’s helpful to have heat as well. Helps the defroster on those damp cool days. And just feels good on the extremities.

In a lot mild climate, I suspect you’d be ok with seat heaters.

Modern seat heaters draw very little current, probably less than 5 amps total. Your cell phone charger uses more power.

[GH85Carrera]

It all depends on your use off the car. If you drive in cold weather, you really need real heat to defrost the windshield, and keep you warm. Seat heaters my warm your backside, but do nothing for your hands and feet or the windows.

The heat on a factory stock Carrera is wonderful. Very fast to warm the cabin, and windows. I drive in weather from zero to 100+ every year. I don't drive on snow or ice, but my car has been snowed on.

If you live in Miami or Hawaii, heat is not going to be an issue.

[Rotor Head]

Thank you all for your input.....I really appreciate your thoughts and I'm thinking further before any moves.

[PeteKz]

I've thought about adding seat heating to my 1973 with comfort seats. I rebuilt those seats and put new seat covers on them last year, but I did not final staple the driver's side seat back, so that I could add the seat heaters later. My problem is finding ones that are high quality. SO much of what's sold on Amazon is cheap Chinese crap that will fail in short order. I don't want to do that job twice (or more). If anyone knows of high quality seat heaters, please post that info.

[dedyplay]

Thank you all for your input..

[356911930]

^^^
I don’t want to seam like a paranoid jerk but this guy has made a lot and I mean a lot of unnecessary comments in a very short period of time as if to only build up his thread count to provide a reliable history for scamming PP members.

Dedyplay I hope I am wrong but you are starting to creep me out. Any chance you have a member to vouch for you?

Or maybe I should mind my own business! Hopefully I am wrong. Flame suit on!

Rahl

[356911930]

Glad to hear that this guy got banned!

Rahl

[Winter]

Originally Posted by blucille

Modern seat heaters draw very little current, probably less than 5 amps total. Your cell phone charger uses more power.

I had no idea, automotive electrical stuff is new to me (I’ve only done a bit of basic residential wiring, like swapping outlets, lighting installation). Thanks for the education!

And, Rahl, I’d noticed those posts!

[Cairo94507]

I have SS heat exchangers on my 3.6 in my car and seat heaters. Yesterday morning was a great example of why I love both. It was cold out on our 100+ mile trip to a friends place to work on another friends car. We were nice and toasty the entire trip with nice clear glass - no fogging. And this was from Auburn to Tracy, CA.

[PeteKz]

Re current draw for the seat heaters: For resistance heaters, "modern" heaters are not any more or less efficient than old ones.

P=IV. If the heat output is 100W (Power), then 100=I(12v), thus I=8.3 amps. If you use 13.5V as the voltage, that's still 7.4 amps. To get down to 5 amps, that would equate to about 60-70W. I don't think that's enough to effectively warm your butt and lower back.

Look at the watts on the ones you see for sale and work out the amps. Even if it's more than 10 amps (120-140 watts), your electrical system should be more than capable of providing it.

[TeeJayHoward]

The seats in my F150 draw about 4A each per seat combined between the top and bottom cushions (~50W). They're inadequate as a sole heating method for Colorado winters, but can make you sweat on a chilly day.

[WMichelsen]

Like Pete asked in #8, does anyone have any direct knowledge recommendations for seat heater kits?

I am reupholstering my seats. Yes, the 911 forced hot-air system is pretty awesome. But I need a toasty butt to balance out my burning feet.

I purchased a cheapo kit from Amazon. It's 4-pads (bottom and back for 2 seats), carbon-fiber elements (whatever). I ran it off my lab power supply, and it spec'd out about 25W per pad. But, I don't think they even got to 75F in my 72F room. Returning them on the next truck back.

What have people installed? And what lessons learned? There's not much to these things. What specs to get? Heating element material, Wattage? The few websites I've found don't disclose anything.

[rswannabe]

I’ve installed seat heaters in many of my cars over the years and run them in both my ‘69 911 and ‘74 911. Don’t use kits that have heating elements with individual wires. The wires can bend and break with wear over time and then the heaters no longer work. Use the ones with carbon mesh heating elements. They do not rely on a single circuit and you can even cut holes in them. The most recent ones I did were retrofitting the sport seats in my ‘74 and I used the Voxx SHSB1 kit. It has worked great and I’ve had zero issues with them. Here is the section on my build thread regarding installing the seat heaters https://forums.pelicanparts.com/porsche-911-technical-forum/993492-74-widebody-hot-rod-build-15.html

As to the OP’s question about going without heat exchangers; I’m not a fan. Having working heaters really helps if you ever want to drive in the rain and keep the windows clear of mist/fog. It also limits where you might drive the car on a road trip (up into the mountains), and can limit the resale of the car into colder climates. There are plenty of high performance heat exchanger options for the 911.

[OsoMoore]

I recently discovered part of why my cabin heat is poor - my heat exchangers are rusting out inside the pass-through holes (for the exhaust header bolts).
The exhaust is still safely passing through and to the Cat without leaking, but the air forced through by the fan escapes different ways, leaving only low pressure forcing it into the cabin.

I wouldn't have noticed if I hadn't dropped a bolt into the inside of the heat exchanger. I guess that's a future fix.

[WMichelsen]

Thanks for the info Brooke.

A bit more inter-webbing indicates 25W/pad (4A) is normal for seat heaters. And, bench test of 75-80 F may also normal. On a bench, there's no seat cushion, or butt, for insulation and heat retention.

They don't do any other work, so energy can only be dissipated as heat, regardless of design/material/whatever. I'll re-check the cheapies I got for uniform heating and durability. Otherwise, from a physics perspective there's not much to consider.

[shoooo32]

I'm running the cheap "carbon fiber" Amazon seat heaters in my SC. They have less draw than my phone charger and will damn near burn you if left on the hottest setting for any period of time. Well worth the $40.

There's value in getting a little warmth without having to run the smelly heat exchangers (or in my case, the Webasto).