Ac blower not turning on sometimes
#1
05-26-2015, 12:48 PM
Ac blower not turning on sometimes
Sometimes when I turn my ac on the compressor will begin to run but no air will come out of the vents. I can run through all speed settings and no change. Then maybe 5 mins maybe 20 mins it randomly works when I turn it on. I have no idea what's going on. Can someone please help me?? 2000 blazer trailblazer edition. I'm not using automatic ac setting but makes no difference if I turn that on it still won't blow but the compressor always turns on instantly. And yesterday I noticed what sounded like a pop behind the dash while the ac was running every 5 mins or so almost sounded like speakers but I turned the radio power off with no change I don't know if it's related or not
Last edited by Andrewwood; 05-26-2015 at 12:52 PM.
#2
05-29-2015, 12:13 PM
Nobody likes to reply on this site it seems like. Not sure what's the point of even asking questions when 100 people look and don't say anything...
#3
05-29-2015, 10:02 PM
Does no air come out of the vents, or no COLD air come out? If no air at all comes out, you may have a problem with your blower motor, or blower motor resistor. Of course if it blowing out of the defroster, or heater and just not the dash vents, you might have a vacuum leak or bad selector switch.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
#4
05-31-2015, 04:09 PM
Does no air come out of the vents, or no COLD air come out? If no air at all comes out, you may have a problem with your blower motor, or blower motor resistor. Of course if it blowing out of the defroster, or heater and just not the dash vents, you might have a vacuum leak or bad selector switch.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
I know it has a full charge. It feels cold coming out of the vent but the blower is for sure not kicking on but only someyimes other times it works perfect. Could the selector switch be bad even though the compressor is kicking on but it's not blowing? Also if the blower or resistor are bad would it work sometimes and sometimes wouldn't?? I have no clue but I ordered a new resistor already since it's the cheapest start
#5
05-31-2015, 06:36 PM
Without having the truck in the shop in front of me, it is hard to tell.
I would start with voltage measurements and wiggle the fuse and switch and all other connectors while taking the measurements. You should have a steady, consistent voltage no matter how you wiggle anything electrical. If your voltage fluctuates when you wiggle or twist any of the wires, you will need to spend some more time investigating those suspect connections.
If it is the electric blower motor itself that isn't working all the time, it is most likely some sort of electrical problem. The blower motor itself is unlikely, as they tend to either work or not. But it is very easy to test. Simply apply 12VDC across the terminals and it should blow at max speed.
The blower motor resistor could be the culprit, especially if the motor seems to work on one or two speeds, but not the rest. Normally, when the resistor fails you will lose one or all speeds, all the time. But the old ceramic resistors have been known to be a bit flakey as they age. Sometimes they will develop cracks and vehicle vibrations can make them switch between working and not.
The blower speed selector could be the issue. It is just an multi-select switch, and if the contacts are old and crusty it would cause the issue of the blower working sometimes and then not working. You can try taking the switch out of the dash and giving it a good spray of electric parts cleaner (I prefer CRC). If the switch contacts have any green crusty crud on them, you will need to clean it off with a soft wire brush (brass preferably). If you see any green crud on the switch contacts, carefully inspect the plug also for the same crud. Clean as necessary.
Don't overlook the electrical connections either, from the fuse panel to the blower speed selector switch, to the blower motor resistor, to the blower motor itself. You could just have something as simple as a loose wire. I have been tracing broken wires in my '97 Blazer for over a year. Slowly but surely I am isolating them and wiring around the breaks.
Intermittent electrical problems are a headache, no matter how you go about fixing them.
I would start with voltage measurements and wiggle the fuse and switch and all other connectors while taking the measurements. You should have a steady, consistent voltage no matter how you wiggle anything electrical. If your voltage fluctuates when you wiggle or twist any of the wires, you will need to spend some more time investigating those suspect connections.
If it is the electric blower motor itself that isn't working all the time, it is most likely some sort of electrical problem. The blower motor itself is unlikely, as they tend to either work or not. But it is very easy to test. Simply apply 12VDC across the terminals and it should blow at max speed.
The blower motor resistor could be the culprit, especially if the motor seems to work on one or two speeds, but not the rest. Normally, when the resistor fails you will lose one or all speeds, all the time. But the old ceramic resistors have been known to be a bit flakey as they age. Sometimes they will develop cracks and vehicle vibrations can make them switch between working and not.
The blower speed selector could be the issue. It is just an multi-select switch, and if the contacts are old and crusty it would cause the issue of the blower working sometimes and then not working. You can try taking the switch out of the dash and giving it a good spray of electric parts cleaner (I prefer CRC). If the switch contacts have any green crusty crud on them, you will need to clean it off with a soft wire brush (brass preferably). If you see any green crud on the switch contacts, carefully inspect the plug also for the same crud. Clean as necessary.
Don't overlook the electrical connections either, from the fuse panel to the blower speed selector switch, to the blower motor resistor, to the blower motor itself. You could just have something as simple as a loose wire. I have been tracing broken wires in my '97 Blazer for over a year. Slowly but surely I am isolating them and wiring around the breaks.
Intermittent electrical problems are a headache, no matter how you go about fixing them.
Last edited by Grandpaswagon; 05-31-2015 at 06:44 PM.
#6
06-02-2015, 12:15 PM
Without having the truck in the shop in front of me, it is hard to tell.
I would start with voltage measurements and wiggle the fuse and switch and all other connectors while taking the measurements. You should have a steady, consistent voltage no matter how you wiggle anything electrical. If your voltage fluctuates when you wiggle or twist any of the wires, you will need to spend some more time investigating those suspect connections.
If it is the electric blower motor itself that isn't working all the time, it is most likely some sort of electrical problem. The blower motor itself is unlikely, as they tend to either work or not. But it is very easy to test. Simply apply 12VDC across the terminals and it should blow at max speed.
The blower motor resistor could be the culprit, especially if the motor seems to work on one or two speeds, but not the rest. Normally, when the resistor fails you will lose one or all speeds, all the time. But the old ceramic resistors have been known to be a bit flakey as they age. Sometimes they will develop cracks and vehicle vibrations can make them switch between working and not.
The blower speed selector could be the issue. It is just an multi-select switch, and if the contacts are old and crusty it would cause the issue of the blower working sometimes and then not working. You can try taking the switch out of the dash and giving it a good spray of electric parts cleaner (I prefer CRC). If the switch contacts have any green crusty crud on them, you will need to clean it off with a soft wire brush (brass preferably). If you see any green crud on the switch contacts, carefully inspect the plug also for the same crud. Clean as necessary.
Don't overlook the electrical connections either, from the fuse panel to the blower speed selector switch, to the blower motor resistor, to the blower motor itself. You could just have something as simple as a loose wire. I have been tracing broken wires in my '97 Blazer for over a year. Slowly but surely I am isolating them and wiring around the breaks.
Intermittent electrical problems are a headache, no matter how you go about fixing them.
I would start with voltage measurements and wiggle the fuse and switch and all other connectors while taking the measurements. You should have a steady, consistent voltage no matter how you wiggle anything electrical. If your voltage fluctuates when you wiggle or twist any of the wires, you will need to spend some more time investigating those suspect connections.
If it is the electric blower motor itself that isn't working all the time, it is most likely some sort of electrical problem. The blower motor itself is unlikely, as they tend to either work or not. But it is very easy to test. Simply apply 12VDC across the terminals and it should blow at max speed.
The blower motor resistor could be the culprit, especially if the motor seems to work on one or two speeds, but not the rest. Normally, when the resistor fails you will lose one or all speeds, all the time. But the old ceramic resistors have been known to be a bit flakey as they age. Sometimes they will develop cracks and vehicle vibrations can make them switch between working and not.
The blower speed selector could be the issue. It is just an multi-select switch, and if the contacts are old and crusty it would cause the issue of the blower working sometimes and then not working. You can try taking the switch out of the dash and giving it a good spray of electric parts cleaner (I prefer CRC). If the switch contacts have any green crusty crud on them, you will need to clean it off with a soft wire brush (brass preferably). If you see any green crud on the switch contacts, carefully inspect the plug also for the same crud. Clean as necessary.
Don't overlook the electrical connections either, from the fuse panel to the blower speed selector switch, to the blower motor resistor, to the blower motor itself. You could just have something as simple as a loose wire. I have been tracing broken wires in my '97 Blazer for over a year. Slowly but surely I am isolating them and wiring around the breaks.
Intermittent electrical problems are a headache, no matter how you go about fixing them.
I received the resistor that was supposed to fit in my truck but after watching a video I looked at the spot on the truck that shows it being removed and I actually have no plug on top unlike the one in the video and the part I received. I'm wondering now if it's different for the system with auto climate control like mine has and ones with manual 1,2,3,4. I'm at a loss here. I am not getting power to the plug at the blower motor I tested it with a test light. My compressor is still running when I turn the ac switch on. Do you know what fuze or where I can find the fuse to inspect. All I see is hvac fuse and the fuse slots are empty for the hvac because I don't have hvac I have auto
#7
06-02-2015, 03:42 PM
Does no air come out of the vents, or no COLD air come out? If no air at all comes out, you may have a problem with your blower motor, or blower motor resistor. Of course if it blowing out of the defroster, or heater and just not the dash vents, you might have a vacuum leak or bad selector switch.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
If it just isn't blowing cold, you may have a charge that is just barely enough to activate the pressure switches. Your first step would be to determine what your high side and low side pressures are. For that you will need a set of AC gauges. If you don't have a set, HF sells a serviceable set that will work for the average shade tree wrench turner.
Without knowing for sure what that state of your system charge is, you are just guessing.
What are the chances this blower control module is the cause? ACDelco 15-8752 GM Original Equipment Heating and Air Conditioning Blower Control Module
Is this the "resistor" on this vehicle?
#8
06-02-2015, 04:39 PM
What year & model? On the glove box door, you'll find the RPO code's for the vehicle. Does yours show "C60" or "C68" in the listings?
#9
06-03-2015, 07:35 AM
There is a group of listings and one does say c68. 2000 blazer trailblazer edition. 4 door 4wd auto climate control
#10
06-03-2015, 04:15 PM
C68 is Automatic Climate Control, which has totally different diagnostics from the C60 manual HVAC system. The HVAC control module sends a PWM, (pulse width modulation) signal to the blower motor control module, (AC Delco part that you listed) which essentially is the "blower motor resistor" with some added electronic goodies inside. Due to the complexity of the C68 system, pinpoint diagnostics need to be done with a bidirectional scan tool. It is possible for the blower motor control module to cause what you're describing, so that might be a good guess. Without the scan tool, unfortunately, that's all it is