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I've tried everything to try to get it to work, replaced the switches, replaced the relay, brand new blower motor, but it won't kick on. This is on a 2002 Trans Am, is there a fuse that I should look for? The switches, and the relay came off another car I have, so I know they are in working order.
My 1996 GM Service Manual says there are two B+ sources for the blower; a 20 AMP HVAC fuse (HOT in RUN) and a Fusible Link (HOT at all times). If the Blower never has B+ at the Purple lead, then you have a B+ issue. If your fuse is good, check the link as it may be open. If the Black wire from the Blower has a resistance of higher than 5 Ohms (to ground) then you have an open / ground issue.
Sounds like there's no blower at all at any speed. If the switch and the relay are known good, the only other common items in the circuit would be power supply to the switch (20A HVAC fuse in left side of dash) or ground to blower motor.
So what I've done so far is replace the relay (which is getting 12v of power), I've replaced the blower motor, I've replaced the switches, I've regrounded the blower motor right next to where it plugs into the motor. The only thing I haven't replaced is the resistor, but where the fan isn't working at any speeds I don't think that is the problem. Right now I am tracking down all the grounds, so far no success. Eseibel67 when I get a chance I'll look for that 20 amp fuse, I didn't realize that was there. Great412 I'll have to check the ohms as well to see if it's open, I'm not sure I understand the B+ thing though. Is that just power going to the motor?
Last edited by Anderson0741; 11-25-2014 at 01:35 PM.
Not as simple as some might think. In high mode, the circuit bypasses the resistor pack completely and appears to pull in a relay-with a separate feed. Here:
Not as simple as some might think. In high mode, the circuit bypasses the resistor pack completely and appears to pull in a relay-with a separate feed. Here:
Thank you, I have been trying to find this! But if it bypasses the relay on high, and it has a live wire going to the relay, but no power making it to the blower motor, what would the problem likely be? Only possibility is a ground right?
Have you tested the blower outside of the vehicle's wiring? Connect it directly to the battery, + & - and see if if spools up. Make sure the blade doesn't chop you up.
If it runs, move on to the wiring. When you put the switch in "high" you should hear the relay pull in. (confirm this is the relay you changed, it's under the dash http://shbox.com/1/high_blower_relay.jpg ). If it pulls in, you should read full battery voltage between the positive & negative pins in the plug that goes to the blower motor.
Have you tested the blower outside of the vehicle's wiring? Connect it directly to the battery, + & - and see if if spools up. Make sure the blade doesn't chop you up.
If it runs, move on to the wiring. When you put the switch in "high" you should hear the relay pull in. (confirm this is the relay you changed, it's under the dash http://shbox.com/1/high_blower_relay.jpg ). If it pulls in, you should read full battery voltage between the positive & negative pins in the plug that goes to the blower motor.
Mine was on the other side, it does have the purple wire that goes directly to the blower motor though. But the last spot I could find with power going to it is the red wire going to the relay, nothing after that
Is this the relay you changed with a known good one?
When it's installed and you turn the switch to high, does the relay pull in? You can tell by click sound or feel.
If yes and yes, is the purple wire to the blower motor plug good? Test with a continuity tester or ohm meter. Should read zero ohms.
Have you confirmed the motor runs when wired directly to the battery?
Blower motor is good, I'm not hearing the relay click off and on though. Using a multimeter how do you check and make sure that it is getting power? I feel like I must've done it wrong
But the last spot I could find with power going to it is the red wire going to the relay
Look at the wiring that pulls in the relay, not the main power to it from the 40 amp fuse under the hood. It comes through the high setting on the fan speed switch but this signal first comes through the selector switch. THAT gets it's power from the HVAC fuse in the instrument panel.
If this fuse is blown or the path to then through both switches has a problem, you won't get any fan speed at all.
When the HVAC system is in any on position and the fan speed switch is in any of the lower speeds, power comes from the instrument panel fuse, through the selector switch, then the fan speed switch, then through the resistors then through the normally closed contacts of the relay then to the blower motor. In this situation, the relay is not energized and the feed from the engine bay fuse is not used. Raising the fan speed witch to higher settings (except high) bypasses one or two resistors.
When the fan speed switch is turned to high, the power from the instrument panel fuse energizes the coil in the relay swapping the contacts. This connects the blower motor directly to the 40 amp fuse from the engine bay.
The power from the smaller fuse is still used but instead of powering the motor through the resistors, it simply pulls in the coil in the relay.
If the small fuse is blown or power through the switches is bad, no blower speeds will work.
11-12-2014, 01:30 PM
Blower motor won't work 2002 Ta 
