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Is there a Relay for the blower fan?


Ed_Strong
10-31-2009, 07:12 PM
I ask because our van started making this clicking noise under the steering wheel (sounds like an old telegraph machine typing morse code) whenever the HVAC switch is turned on regardless of whether the A/C button is depressed or not, so it must be related to the cabin fan and not the compressor.

Funny thing is that there's no change on the blower fan performance, when I hear the clicking, regardless of fan speed, temperature or air direction setting. I didn't try it with the rear HVAC in the ON and OFF position to see if there's a change, I'll try that tommorrow and diagnose some more.
I can't feel any change on engine performance, but a few days after the clicking started I got a DTC P0156, not sure if it might be related or not.

Can you guys give me any feedback if you've had this problem before? I'll really apprecite it.

wiswind
10-31-2009, 08:05 PM
There are 3 factors here.....the fan (hi, low speeds) and diverter (select A/C, heat, vent, defrost) and the blend door (temperature select).

The common "ticking" sound that folks have mentioned is the blend door motor gear being stripped.
A electric motor with nylon gears drives a door that will move to determine how much of the air flows over the always HOT heater core.
The nylon gears can become stripped.....and cause a clicking sound as the motor tries to drive the door into the position that you have selected with the temperature select.
The adjustment knob for the temperature does NOT click....it smoothly moves through the range as you adjust a variable resistor.

The fan SPEED has multiposition switch.....clicks into the positions....and selects which of the dropping resistors that the current will flow through to get to the fan motor.
More resistance is selected for lower speeds.
The dropping resistor for this is located below the glove compartment.
I have pictures that show the replacement process for this part.
The only clicking sound that I can imagine from the fan would be if a leaf or something like that has gotten down into the compartment with the fan blades.

The Diverter doors for the front select for A/C, Vent, Heat, Defrost (etc) are controlled by a switch that also clicks into distinct positions......and this controls solenoids that cause AIR to open and close the diverter doors to cause the air to flow through the desired path.
The air that drives these doors comes from the intake manifold.......and is a strong vaccum.
There is a storage chamber for this vaccum in the engine compartment....passenger side inner fender.
This storage container holds the doors in the desired position when the motor is not running.
If you loose the vaccum source to the diverter doors......the NO vaccum position is DEFROST....
So if the air ALWAYS flows through the defrost (to the windshield), regardless of what position you have selected....then you have lost the vaccum to this system.
A leak at any point in this system can cause this, including a disconnected or damaged vaccum line in the engine compartment.

Ed_Strong
11-01-2009, 10:22 AM
Thanks for the reply wiswind...

But I guess I wasn't clear enough about this problem!

Forgot to mention that I've already replaced the blend motor actuator a year or two ago and the noise I hear is not coming from the center console or the HVAC controls.

If you're sitting on the drivers seat the noise is coming from below the headlight switch somewhere around where the drivers door bottom hinge is, or where your left knee would be while driving! Now, isn't that where the fuse box is? That's why I immediately though of the posibility of a bad relay!

The clicking sound doesn't follow a patern either like the blend door or a leaf on the fan, it's an irregular clicking that only comes up when the Diverter switch is selected into any position (whether is Heat or AC, Floor or Windshield and Vent or Recirculate) and that's what leads me to think it has to do with the blower fan, since the only thing in common within all settings is that the fan is running, except in the OFF position when the noise is not present.

Thanks and I hope that clear it a little better.

I'am working 12hr days now and don't have much time to diagnose and troubleshoot so I was hopping someone already had this issue and could give me the quick fix.

One thing I didn't do was to test with the rear unit ON and OFF to see if there's any difference I'll try that later as I have to leave in a few and won't be back till evening.

serge_saati
11-01-2009, 10:47 PM
Yes, there's a relay in the relay/fuse panel.
1st row, 3rd column for the front blower relay. (no 3)
2nd row, 3rd column for the rear blower relay. (no 6)
2nd row, 1st column for the relay that control the front blower relay. (no 4)

Check on your owner manual. You need to remove the cover before accessing to the relay.
Use flat screwdriver to release the 2 tabs.

To test the relay, you can use the 12V of the car. You should hear 1 click.
Maybe it's not the relay itself, but a bad contact in the relay panel.

12Ounce
11-02-2009, 08:43 AM
I've got that same occassional relay chatter ... related somehow to the vent system ... haven't had time to analyse ... its on the "list".

Ed_Strong
11-02-2009, 07:04 PM
Thanks guys'''

I read the Chilton Manual and it also says that there's a relay for the blower fan! But it doesn't say if there's a relay for the rear HVAC unit or if it's the same relay for both.
It also says that there's also a thermistor in the system but I don't think thats where the problem is.

Anyway today I did more troubleshooting and found out that the clicking problem only happens when at the front panel is set to "Rear Control" for the rear unit and the rear Fan Speed switch (roof by the right side sliding door) is set to the OFF position.

At any other speed selection wether it's OFF or 1 or 2 or 3 at front panel or "User Control" at the front panel and speed 1 or 2 or 3 on the rear Fan Speed switch I don't get any clicking at all.

I drove it for like 15 minutes and the DTC P0156 went away, so I think theres a short somewhere... isn't there a recall for some wiring on the rear AC unit on this vehicles?

serge_saati
11-02-2009, 07:10 PM
there's one relay for the rear and one relay for the front that activate also the relay for the rear.
The clicking sound should come from the front relay.

no, no recall for that.
like you said, maybe a short. At least, you don't have any fuse blown, so it should not be dangerous. The current should be limited by a resistance in the circuit.

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