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Yeah, I took mine apart enough to see that I would have to modify the traces to go any further, so I stopped there. I sort of recall the bulbs being wired in series, so you would want to keep those traces intact.
Since the bulbs activate individually only when the circuits are turned on by each rocker switch, wouldn't it be possible to modify the traces (and re-route the appropriate wires) to take them out of series arrangement?
Perhaps Toyota went with that assumed a shared load for the bulbs on the series circuit? The factory schematic should state what voltage the bulbs would have had running through them.
My idea for repurposing these is to hook each set of two wires into separate relays and not directly into the circuits they would control.
We quickly surpassed my knowledge on the topic. I would guess there's either power or ground going to both bulbs in series, with the other applied by the switch's state. I probably have notes somewhere which wires I followed where... It seems to me that the bulb is the input and the output is what the switch is controlling, and only the latter needs changing. I might just be talking myself in circles now, though.
No, I think you're onto it. I'm making my best guess as well at this point I am thinking that with the way the four wires are arranged from the factory one of them does operate as a ground or both. I will attempt to buy new factory bulbs or LED replacements.
I am wondering, however, if setting both up as switches for relays will provide enough power for the original bulbs to light up. When testing the circuits with a single +1.5V AA battery there was absolutely no illumination. I could try a +9V with the tester though.
Bringing this thread back to ask if anyone with an original SC300 5-speed M/T chassis which came with the seat heater switches in the shift bezel from the factory could take a look at the connector on their seat heater switch harness (not on the chassis harness but on the connector coming from the switches themselves) and list the five-digit factory part number printed on its housing. Or just get a good closeup picture of the numbers on printed on that housing. These can be very small and faintly printed on some connectors and a bright flashlight may be needed to see them clearly.
While the switches themselves are the same for all 92-00 SC's, the factory 5-speeds used a different connector for the seat heater switch option than all of the the automatic SC300's and SC400's. I can't find a picture online but it looks like this in the manual:
If anyone can help with the five digit part number I'd appreciate it! In the Toyota EPC system the first numbers for this should be 90980 but you will not see "90980-" printed on the housing... only the last five numbers of the full part number will be printed somewhere on the connector housing.
Thanks!
Edit/Update 2019:
I'm adding some answer info here in case it helps anyone. The connector part number is 90980-11099 but unfortunately it has long since been discontinued by Toyota/Lexus. I believe it actually may have also been used in a Tacoma application for something to do with an airbag sensor (but I have no confirmation of this) but the only way to find it now would be by going used.
Unless someone happens upon an original SC300 5-speed manual seat heat switch assembly with the pigtail and connector it would probably make more sense going forward to just snag the switches from an automatic SC300 or 400, de-pin the TRAC switch wires and grab another set of Toyota/Lexus connectors that fit the spades on the switch terminal electrodes and those on the SC 5-speed's body harness under the center console just behind the shifter.
And for reference, here is a picture of one of the SC300 5-speed seat heater switch assemblies with the rare 90980-11099 connector.
Last edited by KahnBB6; 03-23-19 at 09:59 PM.
Reason: Added P/N info 2019
02-02-16, 01:18 AM
I would guess there's either power or ground going to both bulbs in series, with the other applied by the switch's state. I probably have notes somewhere which wires I followed where... It seems to me that the bulb is the input and the output is what the switch is controlling, and only the latter needs changing. I might just be talking myself in circles now, though.
