My blower fan runs at low speed only?

It sounds like the linear speed control unit has gone bad which will cause the blower motor to stay on low speed.

Indicator Check

1.While pressing and holding AUTO and fresh/recirculated air switches simultaneously, turn ignition on. Press OFF button to cancel indicator check. After indicator check is complete, system will enter self-diagnostic mode. Stored trouble codes will appear in sequence on temperature display panel.

2.Press fan (down) button to display codes one at a time. If tone sounds when code is displayed, problem causing code currently exists. If tone does not sound when code is displayed, associated problem is past history and does not currently exist. Press OFF button to exit self-diagnostics.

Here is the the location of both the speed resistor and the linear controller so you can swap them out is fix the problem. Check out the images (Below). Please let us know how it goes

Thanks for the quick reply, but the two links you provide do not work.
Clicking them opens window with message "undefined"

The resistor is behind the left side of the dash...
and

Can you identify by the number or letter the blower resistor or its location.
Please let me know if the resistor is actually visible.

Those links are only to acknowledge where I got the info, if you could get to that page, it is the same as I posted for you.

I replaced the blower resistor on my 98 Lexus ES 300 ( and no, it's not behind the left dash. It's above the gas pedal; on the central console, where the carpet ends).

But it did not fix the low speed problem.

What else can cause this problem?
Is there a blower control unit and where is that?
Teh lcd for the fan show additional bars, but the speed stays low.

Before youkeep spending money, did you perform the test I posted? Did you get any codes?

I'm having the same problem with my '98 ES300. I ran the diagnostic and the system returned codes 21 and 42, no tones with either one. I can't tell from the post above what this means, though.

FYI - in the past 20 months, I've had the expansion valve, condenser coil, and compressor replaced in this car, at a cost of over $2k. I hope this blower problem is an inexpensive fix because I've about had it with the A/C repairs on this car.

21= sunload sensor 42= air inlet servomotor circuit. A/C-HEATER SYSTEM -1998 Lexus ES 300 NOTE: If testing is done in a dark area, Code 21 may occur even though system is normal. Shine a light at solar sensor and recheck for Code 21. CODE 21: SOLAR SENSOR CIRCUIT 1.Remove A/C control assembly, leaving harness connectors connected. See A/C CONTROL ASSEMBLY under REMOVAL & INSTALLATION. Turn ignition on. Backprobe terminals A14-11 (Blue wire) and A15-5 (White wire) at A/C control assembly harness connector. See Fig. 5 . Measure sensor voltage. See SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS table. SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Sensor Covered By Cloth 4.0-4.5 Less Than 4.0 (1) As light intensity decreases, voltage should increase. 2.If voltage is not as specified, test solar sensor. See SOLAR SENSOR under TESTING. If sensor is okay, go to next step. Replace sensor if it is defective. 3.Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C control assembly. Retest system. A/C-HEATER SYSTEM -1998 Lexus ES 300 CODE 42: AIR INLET SERVOMOTOR CIRCUIT Actuator Check 1.Remove glove box. Perform RETRIEVING CODES . After system enters self-diagnostic mode, perform ACTUATOR CHECK. 2.Press DEF button to enter step mode and display codes. See AIR INLET DAMPER AIRFLOW table. Air inlet damper operation should be as specified. AIR INLET DAMPER AIRFLOW Code Door Position 0-2 Fresh Air 3 Fresh/Recirculated Air 4-9 Recirculated Air 3.If air inlet damper functions as specified, circuit is okay. If air inlet damper does not function as specified, test air inlet servomotor. See AIR INLET SERVOMOTOR FUNCTIONAL CHECK. Air Inlet Servomotor Functional Check 1.Remove air inlet servomotor. Unplug air inlet servomotor connector. 2.Connect battery voltage to air inlet servomotor connector terminal No. 2 (Red wire). See Fig. 9 . Connect terminal No. 1 (Blue/Yellow wire) to ground. Air inlet servomotor lever should move to recirculated air (REC) position. Transpose battery and ground leads. Air inlet servomotor lever should move to fresh air (FRS) position. 3.Replace air inlet servomotor if it does not operate as specified. If servomotor operates correctly, inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, substitute known-good A/C control assembly. Retest system. Fig. 9: Testing Air Inlet Servomotor

I re-ran the diagnostics with my work light sitting on the windshield and the code 21 went away.

I removed the glove box and discovered that the wiring harness to the servomotor was disconnected. Probably either loose or forgotten from one of the repairs I had performed - the most recent was just 10 days ago or so. Anyway, I plugged it in and the blower speed is back to normal.

I also re-ran the diagnostics after hooking up the servomotor and I still get a code 42. Does this indicate an additional problem? Is there something I need to do to clear this code?

CLEARING CODES Remove ECU-B fuse from fuse block under left side of instrument panel for 10 seconds or longer. After reinstalling fuse, ensure only normal code (Code 00) appears. © 2007 Mitchell Repair Information Co., LLC. Page 1 of 1 A/C-HEATER SYSTEM -1998 Lexus ES 300 8/24/2008 http://www.ondemand5.com/mric/common/asp/printart.aspx

I pulled the ECU-B fuse (which was in the engine compartment fuse box, not the passenger compartment), re-ran the diagnostic, and got a 00. Thanks again.

All set then, very good!