Vent speed is nill at high but works for other speeds

Bad wiper switch,all the best.

Sounds like high blower relay is bad

IF FAN RUNS ON HIGH ONLY AND STOPS ON ALL OTHER SPEEDS THE FAN CONTROLLER (REOSTAT) IS BAD,THE VENT POSITIONS IS A BAD SWITCH ON DASH OR BAD ACUATOR MOTOR ON VENT DOORS

What year is your Envoy ? Probably high speed relay .

If you have a viscous fan hub attached to the fan then it will not be working at high speed as there will be enough air flowing through the radiator to keep things cool. They only really work at high engine loads and slow speeds (hill climbing ) and at stop lights where the air flow is nill

Visit the on-line store, known as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem. 1999 lexus rx300

There is a high speed relay on the circuit, when it goes the fan will only go on medium

possible ignition switch, also need to check ground wire to terminal G200

It could possibly be the switch. Many automotive a/c blowers have a relay to engage the highest fan speed because the high current required will necessitate the use of heavy wiring to and from the blower motor and a heavy duty switch. Check for a high-speed relay and also there might be a circuit breaker in the blower system.

Hope this helps, rhais

Hi.....
On your Vehicle the problem for the FAN speed is NOT the FAN switch.
99.9 % of this problem on cars is the BLOWER MOTOR RESISTOR.
The blower motor resistor give the speed to the Fan.
But on High speed the switch make a By pass of the switch using a Relay for the high speed.
The Blower motor resistor, is located Beside of the Blower motor On the passanger compartment.

If you replace the blower motor resistor you have 99.9% of this will solve your problem.

I'm a Mechanic.

I hope this help on your problem.
Thank you for use fixya...