Cabin (ac/ Heater) Fan Not Working

[rohitjately]

Folks:

I really need your help to figure this out. I took my car for a major service recently and got my 1999 RX 300's cabin filter replaced. Ever since then, I have noticed a problem with my cabin (AC/ Heater) Fan. The fan shuts off on its own every few minutes. Then it swiches on for a few mins and then shuts off again. It also goes up and down in fan speed on its own (without me even touching the fan control)

The service center says they did not do anything that can cause this behavior. However, the problem started right after I took my car home from the service center. The A/C and Heater work fine but they dont blow any air because the fan fails every now and then.

Has anyone else seen this issue? Does anyone have any suggestions on what might the problem be and how to correct it?

Any help is appreciated! This is hot summer time in CA and I am getting grilled without cool air in my car

Regards,

Rohit

[Alexander the o.k.]

1st --check fuse.

It is also possible that it is grounding out somewhere.

That is what it sounds like. Are there any exposed wires where the filter is located?

Is the a/c set in auto mode?

It will do that you know.

Give more details please. When does it shut off?

Check a/c diagnostic codes, and report what you find back here.

TROUBLE SHOOTING

SELF-DIAGNOSTICS

An Electronic Control Unit (ECU) within A/C-heater control

panel monitors system circuits and stores trouble codes in memory if

problems are detected. All codes, except Codes 22 and 23, are stored

in memory. Malfunction is current if Code 22 or 23 is displayed. To

retrieve stored codes, see RETRIEVING CODES. Codes are displayed at

temperature display. See Fig. 2.

RETRIEVING CODES.........

Here's how-----

http://us.lexusownersclub.com/forums/index...?showtopic=3794

Thank you SK.

(And if you can spell Mississauga, in my book, you are NOT an " Official LOC Bad Speller" ) ;)

[mikey00]

I would keep your troubleshooting simple at first. I assume you know how the auto mode works and that it does vary the fan speed depending on the temp set. Being that your problem started after the cabin air filter change, check here first. Removing the cabin air filter is very, very easy. Open the glove box. There is a plastic piece on the back that lifts out. Behind that is a plastic door that you open to get at the cabin air filter. Pull out the filter put the plastic back on and run it a bit and see if you notice any difference. If that doesn't do it, I would try resetting all the electronics next. Disconnect your negative battery cable for a few minutes to do this.

Alexander the o.k.: Are you sure your link for retriveing codes works on a RX? It looks to me like SK was referring to a pre-OBDII vehicle.

[Alexander the o.k.]

Good catch there mikey. My oops.

Disregard. Altho he can, I'm sure try it without any ill effects. Otherwise don't autozone or others do a quick and free scan ?

[rohitjately]

Alexander:

The blower motor issue occurs regardless of whether it is in manual or Auto mode. (I can understand if it happened in Auto Mode only) However, I should let you know that during last week, whenever the blower speed went down, turning the system into 'Auto' would bring the speed up. This did help initially for a couple of days . The fan worked fine on auto mode. However, it started malfunctioning in both modes after that. So now it sucks in either modes

Here is some info on the issue again:

The blower motor goes up and down in speed and then shuts off completely. After a while, it starts up again and stays on. Then it shuts off again. The cycle repeats. I have noticed that this behavior is very prominent during hot days. Not sure if this is a good hint.

Thanks

Rohit

1st --check fuse.

It is also possible that it is grounding out somewhere.

That is what it sounds like. Are there any exposed wires where the filter is located?

Is the a/c set in auto mode?

It will do that you know.

Give more details please. When does it shut off?

Check a/c diagnostic codes, and report what you find back here.

TROUBLE SHOOTING

SELF-DIAGNOSTICS

An Electronic Control Unit (ECU) within A/C-heater control

panel monitors system circuits and stores trouble codes in memory if

problems are detected. All codes, except Codes 22 and 23, are stored

in memory. Malfunction is current if Code 22 or 23 is displayed. To

retrieve stored codes, see RETRIEVING CODES. Codes are displayed at

temperature display. See Fig. 2.

RETRIEVING CODES.........

Here's how-----

http://us.lexusownersclub.com/forums/index...?showtopic=3794

Thank you SK.

(And if you can spell Mississauga, in my book, you are NOT an " Official LOC Bad Speller" ) ;)

[Alexander the o.k.]

Have you tried the diagnostic as suggested? It may not work with your vehicle, but worth a shot. If not, take it to autozone, and have them pull codes. Should be free.

It may well be the blower motor transistor.

This is a diagram for a 1st gen ls, but you get the idea

http://us.lexusownersclub.com/forums/index...ost&id=9738

"In the parts breakdown picture provided above the power transistor might be represented by part # 88630A" (thanks WWEST)

"Your '92 LS400 uses a transistor for controlling all(***) speeds by full HIGH speed, in that case a relay is used to bypass the even the small level of voltage the transistor would drop. With only 12 volts every little bit counts.

Your solid state blower speed control has failed or actually more likely only the final power transistor itself.

"You" can manually only select three blower speeds, the solid state blower speed controller can set ~256 speeds." (thanks WWEST)

http://us.lexusownersclub.com/forums/index...motor++resistor