Question about 1999 Lexus RX 300

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Need to identify the blower motor fuse and or relay for 1999 lexus rx 300

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  • s279mitchell Nov 17, 2010

    thank you for the solution.It makes sense to me.Ive checked everything else and had a feeling I needed to get under the dash.You guys are great.



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The problem is the blower motor linear speed controler, it is a solid state relay. Here is how you replace it and test it from a Lexus repair site. I can almost 100% assure you the blower motor controller is the problem, but here is the testing and the location of part.

Our big issue will be with accessing the blower motor controller, or relay. Lexus calls it a relay, but it is actually a linear controller. for access, removing the glove box may come in handy to access it, but will not make it entirely accessible. To get to it, you will need to basically lay on your back with your head up under the dash on the passenger side looking up. Then the trick is to get your hands up to the relay. I know it sounds crazy, but believe me, we don't like doing this kind of stuff either. There are 2 separate black boxes under the dash. The one just above the passenger foot-well is the blower box and houses the blower motor. To the inside of that is the evaporator box that has the evaporator and heater core inside. The boxes are mode to fit together and form an air duct between them. In this area is where the relay is. It is a box with 2 connectors going to it. One connector will have 2 wires, 1 red and 1 black. These go to the blower motor. The other connector has 3 wires. 1 is a power, 1 is a ground, and the one in the middle is the signal wire. It will be pink with a blue stripe and will be smaller than the other 2. Here is what we need to do once we have accessed this relay. You may have to remove it to get a good shot at the connectors, but we do want the connectors to remain plugged in. We want to backprobe the pink/blue wire. Be careful not to pierce the wiring insulation. We just want to insert the backprobe pin next to the wire until it touches the metal on the end. With that inserted, set the volt meter to AC volts. With the key on (you will probably need help here) hold the red lead to the backprobe pin and the black lead to a GOOD ground, such as an exposed part of the dash frame. Start with the fan control on the lowest setting and slowly increase it towards max. What you should see is a small AC voltage that increases as the knob is turned towards max. If you see this (and I think probably will), then the relay where we are testing will need replacement

Posted on Nov 14, 2010


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