Questionwas driving my vehicle with my heater on an all suddenly it quit blowing air an tried aircondition an it does not work an the defrost don't blow air so i did check fuse an it was good an the kind of vehicle is a chevy 1500 sierra pickup an the year is a 93 please help
James
AnswerJames,
There are a few possibilities that I can derive from your description.
You said you checked the fuse and it was good. Did you check it by looking at it or checking resistance across it with a multimeter? Depending on the type of fuse you are using, they can sometimes look good, but actually be bad. The break may be on the connection to the prongs of the fuse. I suggest trying another fuse in its place just to doublecheck it.
Second. And I am going from the easiest to the more in depth. Check the blower motor ground wire. It will be the black wire leading to the right side door pillar grounding point. There will be several black wires grounded here, so make certain the motor ground is hooked in.
Third. Your blower motor has two wires connecting to it through a plug. Make certain this plug is securely attached and that the wires (black and white) are inserted into the plug firmly. Sometimes on older vehicles, these will work themselves loose.
From this point on you will need a multimeter that measures voltage and resistance to do the checks. Do you have one of these?
What we are going to do is trace the circuit back to the last point you have power.
With the truck key in run position (engine off) and the blower motor switch on high....
Connect your negative multimeter lead to a good grounding point. Any bare metal should work.
Place your multimeter to measure voltage. Check the white wire leading into the fan motor for 12V. If you have good voltage there your issue is with the ground wire, or a bad blower motor.
No voltage? Trace the white wire to your blower resistor. SHould be mounted on your fan housing. test the "B" terminal for voltage. The B terminal is where 2 white wires connect together in the plug. If you have voltage here, you need to replace the white wire leading to your fan, it has a broken connection in it.
Still no voltage? Trace the connecting white wire to your High speed blower relay. This may be mounted on the firewall or door jam on the passenger side or in the junction box under the hood. (usually the firewall) Once you locate the relay... Check the red wire connection for 12V. If you have voltage on the red wire, this relay need replaced, the coil inside it has burnt or the contacts are stuck open. You can try knocking it around and maybe breaking the free, but I suggest replacing it. No power on the red wire? Now we move on to your control head. Do you have the manual on/off switches with the rotating knob speed switch, or is it all digital? If it is all digital, you may be better off locating another one and replacing it, because I would be on here for a while typing out the checks, and I am not too certain how equipped you are in garage electronics. If it is the rotating speed switch, check your switch connections. You should read 12 Volts on one of the connections. My schematics does not break it down that far once we get into the control head. If you have 12 volts on one of the connections, you should have it on another. If you do not find 2 instances of 12V, replace your switch. If you do not read any voltage at all on your switch connections... check your fuses again.
I hope I was able to be of a little assistance. If so, please remember to rate this answer. If I can do anything further now or in the future, please do not hesitate to ask. Or if I need to clarify anything in the explanation above, just let me know. Thanks again and good luck in everything.
