Installing Sheel-Mann seat heater on LX 450 (1 Viewer)

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Hi there chuggers,

So I want to install the Sheel-Mann seat heater properly on a LX450 which it looks like the 450 is not ready to take it on and I wonder how to start. I do know that I have to check under the gear shifter cover to see if I have the correct wiring there but as a newbie:

1. How do I take the gear shifter knob out so I can take the console cover out?

2. How do I connect the Sheel-Mann harness to the battery?

3. Will I die doing it? 😂

I’m not an electrician but have done mechanical work on the rig. I just don’t want to fry the whole truck 🔥. It looks like the LX450 doesn’t come with the proper wiring harness.

I have read some posts in here but it is not quite clear for me where to start. Any help is greatly appreciated.

Cheers 🍻
 

Dirt Ferguson

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You are essentially starting from scratch, ie no wiring for the seat heater switches like some LC models have.

There are a couple different threads about installing seat heaters in an LX if you search.
 
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1) you don't. I'm now realizing it's probably been several years since I last had mine off, but I believe you just lift the console up and then rotate it 90 degrees to clear the shifter.

2) if there aren't existing connectors under there, then run a wire with a fuse as close to the battery as possible into the passenger compartment. The most popular route is the unused rubber cover for what would be a clutch cutout in other markets. Connect that to a regular and trigger the relay using something like the cigarette lighter 12V wire. I like to use Posi-Tap connectors to tap into the factory wiring. Run the output from the relay to the seat heater switch's input.

3) no. Just make sure you have a fuse on the wire, near the battery. To calculate the fuse size, take the seat heater wattage and divide by twelve. That gives you amps. Then add some headroom, say 25% (multiple the calculated amps by 1.25) and round up to the nearest fuse value.

Blue Sea has a nice fuse selection guide:


They also have a wire size selection guide:


The 10% voltage drop is fine for your application. People are always running wires way thicker than they need.

Here's a relay guide:


Just remember that the little pins are the "switch" that tells the relay to connect the big pins together. Your big wire from the battery goes to one big pin and the big wire to the seat heater switch goes to the other big pin. One of the little pins connects to the cigarette lighter 12V wire and the other little pin connects to ground.
 
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My LX 450 came with “factory” heated seats, but it was clearly a dealer or third party install and definitely not up to Toyota standards. There was a thread/ post here recently about it and someone posted the Toyota factory schematic for an overseas variant. It’s a big wiring job to do it correctly.
I have messing with the dash lately on wiring up my ham, and this would be my advice on wiring it up.

1. Find a Toyota sealed relay unit from an auto recycler. Over the years, I found several that just mount on the battery positive post. Had to cut a hole in my battery box to feed the relay battery post mount through. Mounted another style relay to a bracket in the engine compartment. That is what I did for my driving lights, etc. A relay with larger wires is required - 20A min. The schematic I spoke of earlier (attached below) shows both seats (each seat has a lower and upper pad), being feed via one 20A fuse.

2. As others have said, keep the fuse (use a LittleFuse in-line sealed design) as close to the battery as possible. Could be before or after relay depending how close the relay is to the battery. Use quality SXL Automotive type wire and not cheap dollar store wire. I highly recommend using Deutsch connectors even inside the truck as they are compact sealed high quality and easy to unplug. I redid all my “factory” seat wiring using these connectors. Use wire protector on the portions in the engine compartment. If you on adding more electrical features in the future, add more wires in the same bundle for further use. Mark the ends, and draw up a schematic for future reference. I just had to make another run to my aux battery for my HAM radio. Would have been nice if I already had extra wires already run, or even a terminal block inside the truck I could use as I need when installing more electrical items.

3. To do this correctly, I would pull the centre console and shifter console and run all wires from/ through DS firewall, under the dash/ steering column to the centre shifter console then to centre console, and then under the rug up to under each seat. To pull the centre dash fascia, I first unscrew the two top screws where my cup holder is or whatever was there originally. Then there are two screws where the ashtray is I believe (remove mine to install my Cobra CB unit there). The facia will then pop out. Start from the right side and move along the top as there is a clip in the top left corner. There is another centre clip, and one n the lower left corner. To mak it easier to get at all the connectors on the backside, I block one of my tires, and place the shifter into low. Best also to throw down a towel or something soft to protect the fascia. I would also recommend taping up the dash along the left side next to the fascia platevto help avoid scratching it up while you play with removing the connectors. To remove the shifter console there is one Philips screw and one 10 mm bolt on each side of the console. Remove the t-case shifter knob. Pull up and press the trans shifter button to get it past. The centre console uses 3 x 10 mm bolts. Two are at the rear (one each side), and one at the front on the driver’s side. There are also two M10 nuts under the mat in the bottom on the console. IIRC these were special torx or other type nut, but I replaced mine with regular nuts. The LX has the centre CD changer so there is a small fascia surround plate. You need to remove if before lifting the centre console. Gently pry it off from the top with a small flat headed screwdriver or trim removal tool.

This should get you started. If you need the Factory heater switches, I have at least half a dozen various spare sets I could sell you at a reasonable mud price. Just PM me.

2F77D124-8F36-4A63-A779-777E608BC820.jpeg
 
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Thanks everybody for the info. Much appreciated. Electrical is one of the things that I’m not so versed, I’m very green on that stuff 🤮 This job seems to be more intricate than what I was expecting.

Gladly, the seats came with the heater pads installed and the harness with a relay + switch on/off button (round one though). So first thought is, I’m thinking about disconnecting the generic round switch and install the OEM one so it sits nice on the dash panel. It looks like the folks at the factory know that people do that quite often and added a plug on the switch wire that makes it easier to install other switches.

Second thought is, as @Outsane mentioned, the OEM seats are electrical and I believe that I might go down that path when connecting the power source. However, I’m not sure if the harness plug matches the one coming from the fuse box. @Outsane, would you mind sharing your installation process?

Third thought is, what is the best route for the cables from the dash panel to the underside of the seat where the heater wires are? From dash to under the gear shifter cover and then under the carpet maybe?

I still have questions about the installation process but I guess it will make more sense if I post some pics along with the questions. I’ll comeback later and post everything.
 
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You are essentially starting from scratch, ie no wiring for the seat heater switches like some LC models have.

There are a couple different threads about installing seat heaters in an LX if you search
My LX 450 came with “factory” heated seats, but it was clearly a dealer or third party install and definitely not up to Toyota standards. There was a thread/ post here recently about it and someone posted the Toyota factory schematic for an overseas variant. It’s a big wiring job to do it correctly.
I have messing with the dash lately on wiring up my ham, and this would be my advice on wiring it up.

1. Find a Toyota sealed relay unit from an auto recycler. Over the years, I found several that just mount on the battery positive post. Had to cut a hole in my battery box to feed the relay battery post mount through. Mounted another style relay to a bracket in the engine compartment. That is what I did for my driving lights, etc. A relay with larger wires is required - 20A min. The schematic I spoke of earlier (attached below) shows both seats (each seat has a lower and upper pad), being feed via one 20A fuse.

2. As others have said, keep the fuse (use a LittleFuse in-line sealed design) as close to the battery as possible. Could be before or after relay depending how close the relay is to the battery. Use quality SXL Automotive type wire and not cheap dollar store wire. I highly recommend using Deutsch connectors even inside the truck as they are compact sealed high quality and easy to unplug. I redid all my “factory” seat wiring using these connectors. Use wire protector on the portions in the engine compartment. If you on adding more electrical features in the future, add more wires in the same bundle for further use. Mark the ends, and draw up a schematic for future reference. I just had to make another run to my aux battery for my HAM radio. Would have been nice if I already had extra wires already run, or even a terminal block inside the truck I could use as I need when installing more electrical items.

3. To do this correctly, I would pull the centre console and shifter console and run all wires from/ through DS firewall, under the dash/ steering column to the centre shifter console then to centre console, and then under the rug up to under each seat. To pull the centre dash fascia, I first unscrew the two top screws where my cup holder is or whatever was there originally. Then there are two screws where the ashtray is I believe (remove mine to install my Cobra CB unit there). The facia will then pop out. Start from the right side and move along the top as there is a clip in the top left corner. There is another centre clip, and one n the lower left corner. To mak it easier to get at all the connectors on the backside, I block one of my tires, and place the shifter into low. Best also to throw down a towel or something soft to protect the fascia. I would also recommend taping up the dash along the left side next to the fascia platevto help avoid scratching it up while you play with removing the connectors. To remove the shifter console there is one Philips screw and one 10 mm bolt on each side of the console. Remove the t-case shifter knob. Pull up and press the trans shifter button to get it past. The centre console uses 3 x 10 mm bolts. Two are at the rear (one each side), and one at the front on the driver’s side. There are also two M10 nuts under the mat in the bottom on the console. IIRC these were special torx or other type nut, but I replaced mine with regular nuts. The LX has the centre CD changer so there is a small fascia surround plate. You need to remove if before lifting the centre console. Gently pry it off from the top with a small flat headed screwdriver or trim removal tool.

This should get you started. If you need the Factory heater switches, I have at least half a dozen various spare sets I could sell you at a reasonable mud price. Just PM me.

View attachment 3117047

This is very good and detailed info. Thank you!

Since the seats came with the harness, could I just use the cable connecting to the OEM seats as a power source and run the switch cable under the carpet and gear shift cover to the dash? I’m intending to install the switch on the dash panel as the LX came with the sub-woofer and there is no space for the switches on the center console.
 
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As @Outsane mentioned, he tapped into the power lead for the power seats. Can’t recall what they did for mine, but I’m guessing they did something similar as there was definitely no new power leads on to the battery. Do you now how much wattage/amps the heating elements are spec’s at? In this thread it says 15A. Have you seen this thread? Seems like a detailed explanation.


Me personally, if it is really 15A per seat, I would likely run a dedicated circuit for each seat as you start to need large wire diameters for longer runs. See chart below. In your original post, you stated you wanted to do it properly. To do it properly takes more time, more skill, and more money, but is worth it when it comes to electrical because the last thing you want is your vehicle burning to the ground and possibly taking your house or someone else’s property with it.

848F7F50-4A13-4126-9443-40E813F1C059.png
 
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As @Outsane mentioned, he tapped into the power lead for the power seats. Can’t recall what they did for mine, but I’m guessing they did something similar as there was definitely no new power leads on to the battery. Do you now how much wattage/amps the heating elements are spec’s at? In this thread it says 15A. Have you seen this thread? Seems like a detailed explanation.


Me personally, if it is really 15A per seat, I would likely run a dedicated circuit for each seat as you start to need large wire diameters for longer runs. See chart below. In your original post, you stated you wanted to do it properly. To do it properly takes more time, more skill, and more money, but is worth it when it comes to electrical because the last thing you want is your vehicle burning to the ground and possibly taking your house or someone else’s property with it.

View attachment 3117814

Thanks for the info @canman. I checked the post you mentioned, good info in there as well.

This is my first electrical job in the rig and I don’t want to mess it up but also want to install what I got and learn in the process. I have very basic skills with electricity and wouldn’t mind starting from the very basic stuff. Internet is helping.

I took some pics of the harness that came with the aftermarket seats and next step will be to check the harness available under the OEM seats so hopefully, there will be some compatibility there.

Here are the pics with some questions:

08C5FE88-1F17-48B7-A891-B87A4A56CA59.jpeg

1. This are the plugs that came with harness. Should these be connected to the OEM harness located under the seat?

9D2C42F3-CEB5-4040-ADA1-7AF08773DA5A.jpeg

2. I believe this is the ground (black) and hot (red) wires. I might be very wrong here though. Where do I connect the red one?


180E908B-F218-450D-9B3F-AC26216D2D04.jpeg

3. The relay that came with the harness.

A8C1EB2B-B5A6-4433-946C-E2F2E477B72A.jpeg

4. The switch which I’ll remove to install the oem switch instead.
05A6271E-5BCC-4CA2-ABA4-A18326AC73CC.jpeg

5. The overall view of the harness.

These are all rookie questions but appreciate any info on this.
 
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Hard to explain what to do. Red is typically power (+12VDC), and black is typically negative/ground.

If what @Outsane works, then you can try his approach, but technically if you are going to tap into the power seat circuit, I would first check to see what value it’s fuse is sized at and check to see if by adding the heated seat circuit to it will not overload the fuse. For example, my 1997 Lexus Electrical Wiring Diagram manual shows a dedicated 30A fuse (not shared by any other circuits/devices). This fuse is for both seats.

What size fuse is in the fuse holder, or what size fuse do they recommend?

I can see by the heater switch, you have what appears to be two settings (Low & High) plus an “OFF” setting I assume. That would be a 3 position switch. If it indeed is a three position switch, things get complicated quickly, because you now need a potential second relay. One for the “low” setting, and one for the “high”. I believe there are single relays that can handle that type of application, but I have been out of the automotive sector for over 20 years now. The OEM switches will also have a wire for the bulb light, and of course a ground wire. Have a look at this 3 position Toyota/Lexus seat heat switch. There are 6 wires exiting the pigtail connector. Will you be able to identify what wire is for what?

4BB9CAA7-22F4-40D2-B4D1-DB52AC04F93B.jpeg
BE022FFE-51CC-454C-BB46-C11F2B5B7404.jpeg
 
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The switch which I’ll remove to install the oem switch instead.

I don't know your plan specifics, but I'd install it with the included switch to start with. The last thing you want to do is mis-wire a Toyota switch and not know if the rest of the circuit is wired correctly while trying to debug the problem.
 
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I don't know your plan specifics, but I'd install it with the included switch to start with. The last thing you want to do is mis-wire a Toyota switch and not know if the rest of the circuit is wired correctly while trying to debug the problem.
Good idea, will do that.
 
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Hard to explain what to do. Red is typically power (+12VDC), and black is typically negative/ground.

If what @Outsane works, then you can try his approach, but technically if you are going to tap into the power seat circuit, I would first check to see what value it’s fuse is sized at and check to see if by adding the heated seat circuit to it will not overload the fuse. For example, my 1997 Lexus Electrical Wiring Diagram manual shows a dedicated 30A fuse (not shared by any other circuits/devices). This fuse is for both seats.

What size fuse is in the fuse holder, or what size fuse do they recommend?

I can see by the heater switch, you have what appears to be two settings (Low & High) plus an “OFF” setting I assume. That would be a 3 position switch. If it indeed is a three position switch, things get complicated quickly, because you now need a potential second relay. One for the “low” setting, and one for the “high”. I believe there are single relays that can handle that type of application, but I have been out of the automotive sector for over 20 years now. The OEM switches will also have a wire for the bulb light, and of course a ground wire. Have a look at this 3 position Toyota/Lexus seat heat switch. There are 6 wires exiting the pigtail connector. Will you be able to identify what wire is for what?

View attachment 3118239View attachment 3118240


Ok, will take your points in consideration when installing it.

After researching the net, I found some diagrams from Toyota and the seat manufacturer. With the Toyota one I can see what wire is for what in the switch pic that you posted.

A74D3F75-520F-4E46-9331-632777AF41BC.png




C6E963DD-8CC2-4BD0-81FA-133B7CC9E2C8.png
 
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And here is the seat manufacturer diagram:

54068A54-6403-4988-9EE6-DB2AE5D2EA35.png


I think after checking these things are starting to make sense.

Another newbie question, how do I connect the power wire in the fuse box? The diagram says 15A per seat so I believe I have to find a slot with 30A fuse in the box for the two seats or two slots with 15A fuse each. Is that right?
 
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Those Sheel Mann pics aren’t really clear to me about the installation, but it is good to see it is making more sense to you. Even the Toyota explanation is fuzzy for me. Not your simple on/off circuit that’s for sure.
I’ve never added a fuse to the factory fuse box, but if you can purchase the terminal for a fuse base that would be the cleanest installation. When there is better light out, I take a pic of the relays I added to my battery plus a couple of skates I have lying around.
 

haulin auss

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I personally wired my Scheel-Mann seat heater elements directly into the OEM seat heater circuit. I did it the same way as Toyota - elements are in parallel (12v) when on high and series (6v) on low.

The OEM circuit is rated for 20A and also includes the rear heat. Since my rear heat is disconnected, I swapped the 20A fuse for a 15A fuse and haven't had any issue with blowing fuses with both seats on High for several hours. The seat heaters may be capable of 15A per seat but I'm certainly not seeing that in practice...
 
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Here are some pics of Toyota relay assemblies I installed on my truck and a spare that doubles as a battery hold down.

23FEC22A-008A-4F3E-A7E4-DB10C28BAE8E.jpeg

BA8D75F5-4B2A-4BED-B977-F038036B3254.jpeg


24971C0B-4D7C-4A96-BB13-864145D8BCF3.jpeg
C18A8311-902F-4DC1-9644-A8A0AE412677.jpeg

DE9C2A2B-469C-4455-839D-853D6BEC2581.jpeg
 

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