Diagnostic of Broken Lumbar Support Switch in 1999 4Runner Limited

[Nairn]

Hi,

I just bought a 1999 4Runner (Limited, V6) and my lumbar support switch in the power seat on the driver’s side does not work. Normally I would live without this functionality, but the seat is uncomfortable if I sit in it for a long period of time. I don’t have cash right now to take it to the local Toyota dealership to get it fixed.

How can I tell if the switch is the problem as opposed to the wiring or the motor? The rest of the power seat works correctly. If I test the switch and wires with a multimeter, what would I be looking for (i.e voltage, resistance)?

Thanks

[jetwhine]

Nairn,

Wtih power on, voltage no more than 12V. Power off, Ohms/resistance or continuity.

[Nairn]

Ok, so I tested the wires and the switch. There are four prongs that connect the switch to the wires. I do not have a background in electronics. Can anyone tell what these results mean?

1) Wires

a. Voltage: I turned on the power in the 4Runner and make a connection between one of the wire prongs to a ground (truck frame). Three of the wire prongs had no voltage and one had 12 V of voltage (lower left prong).

b. Resistance: I tested between the various wires. Top and bottom of each side showed resistance readings. Across and diagonally did not have any resistance.

2) Switch
Resistance: I tested the resistance between the various prongs with the switch in the off (middle) position, the ‘ lumbar move in’ position, and the ‘lumbar move out’ position. Some of the positions showed resistance readings while others did not.

[jetwhine]

Nairn,

Pin #4 to ground has power when turning key on. When you put the switch to the forward position you should have power at pin #2 to ground. When you put the switch to the rearward position you should have power at pin #1 to ground. Pin 3 is always ground. If this checks out then get access to the motor and see if you have the same results at the wire connection at the motor, there should be only two wires one light blue and one light blue and orange. When you put the switch to the foreward position you should have power at the light blue wire. When you put the switch to the rearward position you should have power at the light blue and orange wire. If this checks out then you have a bad motor. (Note: all this is done with the key switch on). Hope this helps.

[Nairn]

I tested the wires with jump wires (two 20 gauge wires). I hooked up one wire to the upper left (ground) and upper right (motor wire) and the other wire to the lower left (12V power) and the lower right (motor wire). Nothing happened. I tried a couple of different combinations with the same result.

Does this mean my motor is dead? How can I replace my seat’s motor?
Post 3a

I added jump wires between the switch and the wires coming out of the seat so that I could test the voltage as I operated the switch (4Runner power on).

Pin #4 Lower Left (power, 12V)
Pin #1 Lower Right (wire to motor)
Pin #2 Upper Right (wire to motor)
Pin #3 Upper Left (ground)

Results:
a) At all times, I get 12V on the Pin #4 Lower Left wire.

b) With the switch in forward (out position) I get power (12V) at both Pin #1 Lower Right (wire to motor) and at Pin #2 Upper Right (wire to motor).

c) With the switch in Reverse (in position) I get NO power at both Pin #1 Lower Right (wire to motor) and at Pin #3 Upper Right (wire to motor).

Does this suggest the issue is more likely caused by the switch instead of the motor? I have not been able to access the wires at the motor? How do I gain access to the motor?.

From a suggestion on another forum, I also tested by running jump wires from Pin #4 Lower left (power, 12V) to the one of the motor wires (Pin #1 or Pin #2) while the other motor wire was hooked up the ground. Nothing happened.

Thanks!!

[jetwhine]

Nairn,

My thought is that the lumbar is already forward and can't run back because the switch is bad. With not having power at pin #1 when you select rearward movement then I would suspect a bad switch, and possibly a bad motor. To get to the motor you might have to take the seat out of your rig and put it on the bench to work on it. I would start with the switch it is the most accesable.