Problem with fan on 98 z71
kangoosehnter
11-02-2006, 09:11 AM
I am having a problem with the heater/ac blower or fan. When I first start the truck and turn on the fan it will blow air just fine. After awhile, maybe 30 sec. maybe 5 min. the fan will quit blowing any air. If you turn it off for awhile, it will begin working again. Any ideas on what may be the problem and what it takes to fix it.
ChevyWonTon
11-02-2006, 09:54 AM
Sounds like an auto-reset circuit breaker in the fan circuit. Does it matter what fan speed you're using as to how long it takes to cutout? I suspect high speed may cutout sooner, so please confirm.
Also, how long does it take with it off before it will start to work again?
It is possible that your blower motor is starting to fail and is drawing more current than usual, causing a circuit breaker to trip. On the other hand, if there is a circuit breaker inline, it also might be starting to fail.
Hopefully, someone else can confirm if there is indeed a circuit breaker in the blower fan circuit.
Also, how long does it take with it off before it will start to work again?
It is possible that your blower motor is starting to fail and is drawing more current than usual, causing a circuit breaker to trip. On the other hand, if there is a circuit breaker inline, it also might be starting to fail.
Hopefully, someone else can confirm if there is indeed a circuit breaker in the blower fan circuit.
ChevyWonTon
11-02-2006, 10:20 AM
I looked at the wiring diagram for my '93 C3500, and I don't see a circuit breaker anywhere in the wiring diagram for the blower. It's fed from the same 25 Amp fuse as the AC/Heater system.
If your '98 is the same, then I would look at the blower motor itself to see if it has an integral circuit breaker within the motor unit. Otherwise, I'm at a loss to explain the wierd "on again / off again" behavior...
Unless...it's not really related to how long the fan runs. In that case, it just might be a loose connection and not related to running time at all. However, I think you would have given a different description of the problem in that case. Like, sometimes it wouldn't work from the get-go; that doesn't sound like the problem you're having.
I vote for the Blower Motor! :iceslolan
If your '98 is the same, then I would look at the blower motor itself to see if it has an integral circuit breaker within the motor unit. Otherwise, I'm at a loss to explain the wierd "on again / off again" behavior...
Unless...it's not really related to how long the fan runs. In that case, it just might be a loose connection and not related to running time at all. However, I think you would have given a different description of the problem in that case. Like, sometimes it wouldn't work from the get-go; that doesn't sound like the problem you're having.
I vote for the Blower Motor! :iceslolan
777stickman
11-02-2006, 10:28 AM
In the Low, Med1 & Med2 positions the fan is powered by the HTR-AC 25A #12 fuse in the IP fuse block and goes thru the blower resistor pack which controls votage to the fan for speeds. In the High position the resistor pack is bypassed and the Blower High Relay is energized suppling a full 12 volts from the 50A #3 fuse in the Underhood fuse block. There are no self reseting C/B's in the circuit.
If the fan is working in all positions and stops and won't run in any position, I would suspect the motor or the switch module.
Let us know..........Steve
If the fan is working in all positions and stops and won't run in any position, I would suspect the motor or the switch module.
Let us know..........Steve
kangoosehnter
11-02-2006, 10:47 AM
The amount of time it runs before it quits and how long it takes for it to start working again varies all the time. The fan actually seems to run alittle longer before quiting when it is on high.
Where is the blower located and is there anything I could do to test and see if it is actually the blower motor? Thanks for your helpl.
Where is the blower located and is there anything I could do to test and see if it is actually the blower motor? Thanks for your helpl.
777stickman
11-02-2006, 11:41 AM
You can pull the switch module out and jumper the brown wire to any of the other wires and see what happens. If you do this the key will have to be in the "run" position.
Yellow wire is Low, tan is Med1, light blue is Med2 and orange is High.
Yellow wire is Low, tan is Med1, light blue is Med2 and orange is High.
kangoosehnter
11-02-2006, 12:52 PM
I just went out to go home for lunch and it seems that the blower has now completely quit working. Nothing happens on any setting. Anyone know where the blower motor is located at?
ChevyWonTon
11-02-2006, 01:57 PM
I just went out to go home for lunch and it seems that the blower has now completely quit working. Nothing happens on any setting. Anyone know where the blower motor is located at?
Based on my '93 truck, you should find it at the far-right side under the dashboard and behind the glovebox. It sounds like it is a pretty tight fit to get it out, but it doesn't sound impossible.:banghead:
Based on my '93 truck, you should find it at the far-right side under the dashboard and behind the glovebox. It sounds like it is a pretty tight fit to get it out, but it doesn't sound impossible.:banghead:
ssatch
11-02-2006, 03:20 PM
i've got the same truck, it's a GMC, don't know if yours is...my blower stops and starts on its on also and i'm not sure what speed or speeds....also when on #3 speed or med high it will switch to high and then sometimes switch back on its on....i believe that i have read on some forums and maybe here that it could be the control switch for the fan or maybe some bad solder connections on the printed circuit board... or carbon tracks building up on the board... one of these days i'll get around to checking on it...lol....but you might want to check the controls....hope this helps...
777stickman
11-02-2006, 03:55 PM
http://www.automotiveforums.com/vbulletin/showthread.php?t=638414
You both need to read this thread and start checking for power at the blower before you start replacing stuff that may not need to be replaced. Although this tread does not address your complaints it may give you some insight into switch problems. My previous post about removing the switch and jumpering the wiring would answer your ?'s and give you an opportunity to have a good look at it...........Steve
You both need to read this thread and start checking for power at the blower before you start replacing stuff that may not need to be replaced. Although this tread does not address your complaints it may give you some insight into switch problems. My previous post about removing the switch and jumpering the wiring would answer your ?'s and give you an opportunity to have a good look at it...........Steve
Whoaru99
11-02-2006, 04:06 PM
If replacing the blower motor on a newer rig is anything like replacing it on my 1994, have fun.
My suggestion is to pay the extra and go with a factory replacement blower. I used an aftermarket and it crapped out within a year and was just as noisy brand new as the factory one was when it went bad.
Being somewhat of a PITA to replace, I didn't relish the possibility of replacing an aftermarket blower every year or two even if the part was covered by warranty (since I still had to replace the darn thing) so I went GM and have not had any trouble for a couple years and it's quiet - relatively speaking, that is.
My suggestion is to pay the extra and go with a factory replacement blower. I used an aftermarket and it crapped out within a year and was just as noisy brand new as the factory one was when it went bad.
Being somewhat of a PITA to replace, I didn't relish the possibility of replacing an aftermarket blower every year or two even if the part was covered by warranty (since I still had to replace the darn thing) so I went GM and have not had any trouble for a couple years and it's quiet - relatively speaking, that is.
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