Blower only runs at M1 speed at M1, M2, & High setting

[rrrandy]

My 2006 Vibe AC works great at the M1 setting. The AC turns on and off, the recirculate works as expected. The blower does not work on low (neither does the AC). It does work at M2 and high, but only blows at the M1 speed.

I have learned a lot from this forum about how to replace the major components. I have checked the fuse, replaced the blower, replaced the blower relay, replaced the resistor, and even replaced the control module. None of these has made a difference, the blower turns on at M1 and runs at that speed at M2, and high. It is off at the off and low setting. Does anyone have any ideas what to check next?

[joatmon]

Welcome to genvibe.

Sucks to have tried all those various things and still have the same issue.

What control module did you replace?

Since you've already replaced the blower, and resistor, I'd be inclined to suspect the fan speed switch.

The resistor has four pins, labelled A B C and D. The fan speed switch grounds one pin A for speed M1, pin B for speed M2, pin C for High. D is wired to ground. C is also wired to one side of the blower motor. You could check the resistor wire harness to see if the fan speed control applies a ground like it should.

The resistor has several resistors in series. There's resistance between C and B, B and A, and A and D. When the switch puts a ground on pin C, that's also directly tied to the blower, so the fan should run a full speed. When it grounds pin B, then the blower is grounded though the C/B resistor, so it runs a bit slower. If the switch grounds pin A, then the blower is grounded through both the C/B and the B/A resistor.

The fan speed switch is a double throw, one throw send a ground to one of the resistor pins, the other throw sends a ground to the HEATER relay. When the switch is off, the heater relay is open, when the switch is at any speed (low, M!, M@, and High) the switch sends a ground to activate the Heater relay. So when the switch is set to low, the relay should activate, and since no ground is sent to the resistor, the blower is grounded though al the resistors C/B, B/A and A/D

So, its possible that the switch is bad, not grounding/activating the HEATER relay on Low fan speed, and only grounding resistor pin A at all the other fan speeds, or possibly all fan speeds

[rrrandy]

Thanks for the reply. We replaced the AC / Heater control switch (the one with the selector dials) over the weekend with no change in symptoms. I am wondering if the wiring on the resistor has been kicked since it is relatively close to the passengers feet. My next step is to start checking the wiring connectors and then tracing wires. Do you have a recommendation for a good schematic?

[joatmon]

Do you have a recommendation for a good schematic?

attached, below

[rrrandy]

My son has taken the car out of town for a summer intern job so I'm not going to be able to do many diagnostics for the summer. I am suspicious of the G200 ground (or the path to it). If it were bad that might explain why the blower doesn't come on at low setting. It wouldn't explain the lack of variation between M1, M2, and high.

Thanks for the schematic. I will hold onto it for future reference.

[jolt]

Place a jumper wire on the wht/blk wire at the fan switch (connector pin #5) to a good ground and see if it works properly. You did ohm out your new fan switch to make sure it was good before you installed it? Bad grounds can cause all kinds of weird problems as the electricity is looking for the path of least resistance and will back flow through other power wiring looking to ground itself. Bad connections at plugs and broken wiring will do the same thing when it is on a ground wire.

[rrrandy]

I know a lot of time has elapsed since the original post on this topic. This problem had “healed” itself after tugging on some wires trying to find a bad ground connection and the problem appeared to be resolved. I recently had to replace the recirculation damper motor, so over the last few years I believe I have replaced every component in the Vibe blower motor circuit (blower, switch, relay, resistor, and now recirculation motor). After replacing the recirculation motor, the original single blower speed problem returned. Realizing this had to be a wiring problem I got some help from my son so one of us could probe with a multi-meter and the other flip switches. We had to remove the radio again to get to the connectors on the back of the switch. Jolt (post above) had indeed nailed the problem of a grounding issue. We found 8000+ ohms between the switch terminal 5 and G200 on the schematic (bottom left). It should be near zero ohms. There is no practical way to replace this wire which is inside a large bundle, and how or where it failed still puzzles me. We cut the wire near terminal 5, installed a spade connector, and ran a jumper wire to ground at G200 located behind the instrument cluster; drivers side.
I had put this project off for a long time because I needed to pull the radio (not particularly hard) and have the extra hands and brain power to work through the schematic testing each path . Now everything works as expected, Whew!