Help me make sure my Alibaba seat heaters won't burn down my truck...

Hello fellow Tacoma enthusiasts - I'm hoping someone with more electrical savvy than myself can help me make sure the seat heaters I bought off Alibaba a year ago won't burn down my car prior to installation. I know there are numerous threads on this topic but after scouring the web for days, I cannot find an answer to my question.



Long story short - I've held off on installation of these heaters until I got some fancy Clazzio leather seat covers. Well the covers are now (a year later) in the mail and I need to get my install sorted. I was a bit excited/skeptical to find a kit on Alibaba with the OEM style rocker switches. My initial cause for concern was that I received a kit with three wires - a ground, an ignition, and a 12V power. Most kits come with a 4th illumination circuit. This made me question everything and pin out the circuit to create a schematic (see pictures below).



So from my one electrical course taken 15ish years ago, I recognized this circuit as a voltage splitter. Essentially operating the switch on the low setting will trigger the relay and set up a series resistance circuit with 12V across two 5 ohm resistors resulting in a 1.2a current draw (shown in blue and green on my schematic - blue is the signal and green is the heating circuit). This is great. My concern comes with the high setting. The high setting creates a parallel resistance circuit with 12V across two 5 ohm resistors resulting in a 4.8a current draw (!). It does not engage the relay other than using it as a passthrough for ground! Note that the switch will always be illuminated with the ignition on (I can live with this).



My understanding is that relays are used to avoid high current draw situations. I cannot find current ratings for the OEM style rocker switches but I'm worried 5 amps (4.8 technically) is pushing it. Obviously my first concern would be a car fire, but a close second is having to redo all of this after installation because the switches burned out.



Can anyone smarter than me provide some feedback regarding that current draw going through the switch? Did I pin the schematic out wrong? Can these switches handle 5 amps without issue? Can I rewire the relay and/or replace it with something that works? If I have to buy a new kit I wouldn't be opposed, but it would be nice to avoid!



Thanks all for sticking it out with me.

 

I'm going to try and help from the seat of my pants here. I haven't wired my heated seats yet, but they're just simple on/off style (but do draw 5A).

I finally was able to follow your drawn circuit. It'd be a little easier to follow by showing everything that goes to ground w/ a nearby ground symbol. Once I got it, it makes sense with your understanding. The relay in this case does not have the purpose to carry load power or handle high current. The relay's only purpose is to allow the circuit to switch between having the loads in series and having the loads in parallel.

What this means is, yes, your switch needs to be capable of handling 5A or about 70W (14V*5A). I'd either find a spec sheet of the switch to verify or bench test it myself. FYI, the basic Contura II rocker switches I like to use that are about $14 are rated for 20A @ 12V. 5A is not a crazy amount for a switch to handle.

This type of toggle switch is the same style switch (on-off-on) you'd need for hi/lo that's rated for 30A @ 12VDC. Just another example of a simple switch that would handle your load w/ ease.

$18 30 Amp Toggle Switch DPDT 3 Position On-Off-On

https://www.amazon.com/GAMA-Electronics-Toggle-Switch-Position/dp/B001PNMC16

 

I dunno. You may be overthinking this. My concern was proper fuse sizeing.

 

Thanks for the feedback! Yeah sorry for forgetting about that ground - glad you were able to figure it out. Specs on that switch are hard to find. I think they were originally designed for RAV4’s so I’m trying to hunt down a 2016ish RAV4 heated seat schematic to look at the current draw. Thanks again!

 

@caribe makaira

 

So I think I was able to find a schematic for the RAV4 switches. I don’t know the resistance of the heater pads but seeing as how they’re run directly through the switch and protected by 10 amps and utilize similar parallel vs series circuits I think I should be good to install. Thanks all for your help.