2005 Vibe heater fan not working

[gtm]

The heater fan on my 2005 Vibe worked intermittently for a few days then stopped completely. All the fuses are good. Hooked the motor directly to current. It is good. Replaced the resistor. Removed and tested the motor relay. It is good. I assume the next step is to check the speed control switch. Can anyone tell me how to test the switch? Any ideas on what else may be wrong? Thanks for helping.

[joatmon]

Welcome to genvibe!

I attached a copy of the 2004 Matrix heater wiring diagram, which should be the same for your 05 Vibe

The blower motor gets 12V from the HEATER fuse which then goes through the HEATER relay. That relay is activated by the GAUGE fuse. If the GAUGE fuse was blown, you'd have more problems than just the blower. The GAUGE fuse gets power when the ignition switch in in the ON/Run position and it enables multiple other independent circuits

You said you checked the HEATER relay. It's above the glove box, there's four relays, the heater relay is the one that's bigger. Some people have had the TAIL relay in that relay block work loose and lose their tail lights, might happen for the heater relay as well I suppose. (There are pics in viewtopic.php?t=5078 ) You could probably reach up and over that relay block to make sure they are all fully seated without having to unscrew the block from the dash frame. The fan relays in the under hood fuse block are for the engine cooling fan, not the HVAC blower.

The HEATER fuse is one of the three giant fuses in the awful to access under dash fuse block (the one closest to the micro fuses)

The blower motor gets ground from the Fan speed switch. When the speed is set to HIGH, it bypasses the blower resistor and puts no resistance in the motor circuit, so the fan runs at max speed. When the speed is set to second highest, the ground routes through a piece of the blower resistor, and at the next lowest speed it runs through more of the resistor. The more resistor, the slower the motor. When a resistor goes bad, the fan should still run at the highest/max speed

I'd probably disconnect the wire from the blower motor. Turn the fan speed to the highest setting. Then turn the key to ON/Run (engine doesn't need to be started) and check for 12V on one of the pins (The diagram says it would be the solid black wire, but you could check both) Then turn the key off and check for continuity to ground, (which the diagrams says it should show up on the black w/white stripe wire) The one that was 12V should be open circuit, the one that wasn't 12V should be ground. If its working right,these two tests would get you 12V on one, ground on the other, and if you do then the blower motor is suspect.

If you don't get 12V, then it's either the HEATER relay or the HEATER fuse, or it could be the speed control switch not sending ground to activate the HEATER relay.

If you don't get ground at the blower when the speed switch is set to highest, then the fan speed switch is suspect.

Or it could be some wire damage somewhere

[gtm]

Thanks for your quick reply. Your information is excellent. If I determine that the control switch is the likely culprit is there a way to test it or should i just replace it?

[joatmon]

I'm inclined to not suspect the switch, I think if yours is bad it might be the first bad one reported here in 21 years of genvibe

That being said, here is a pic showing an excerpt from that wiring diagram and a portion of an ebay pic of the back of the HVAC controls with what I think are the corresponding pin numbers

fancon.jpg (36.93 KiB) Viewed 1286 times

I don't know why there's no pin 7. You would want to verify the pin numbers in the pic with the wire colors in the cable that connects to it. Not shown in the wiring diagram is pin 8, which should be a green wire for the backlights. If the HVAC panel lights up, then you're getting a ground to it.

To test the switch itself, get access to the back side. This is the hardest part. I once tried to pull that thing and gave up, if you can't figure it out maybe reach out to genviber muttleytm, who recently pulled and reinstalled one in viewtopic.php?t=48586

You may be able to test it without pulling it, using a mirror and perseverance.

Either way, disconnect the electrical connector, and use a multimeter to check for continuity between different pins on the back of the fan speed control for each of the switch settings

Code: Select all

Fan Speed   pins that should have connectivity/short
OFF           None
Low           5 and 6
Med 1 (M1)    2, 5, and 6
Med 2 (M2)    1, 5, and 6
HI            4, 5, and 6

One other thing to consider. Sometimes, people have reported here that their fan stopped working, or worked intermittently, and that smacking the motor got it working again, at least for a short time. Attributed to bearings or brushes in the motor wearing out. You said the motor bench tested fine, but perhaps the process of pulling it, or the orientation of the motor for the bench test let it work, but when mounted in the car it didn't. It would be worth trying to put 12V on the motor connector while mounted in the car to verify the fan works when installed

[gtm]

As stated before, I had replaced the resistor and motor and had tested the relay (it clicked when I applied power to it). After reading your last post I decided to replace the relay before messing with the switch. That turned out to be the problem. It all works fine now.
Your information was thorough and very helpful. I now know how the system works and how to troubleshoot it. Thanks for your help.