1999 Tahoe Blower (high speed only) Stopped Working
- Thread starter rage
- Start date
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Erich777
TYF Newbie
23 to 27 Amps??? Really?? I measured mine at 13.9 Amps and thought that might indicate a bad motor! (due to high current draw) If other motors measure this high, Ill go with the bypass and save myself the hassle of buying a blower motor and another switch!
Does anyone know the resistance values of the stock resistor?
Does anyone know the resistance values of the stock resistor?
SunlitComet
OBS Jedi-Do Good
The reading I posted was service manual info and I would not be surprised if that was starting current. On the other hand the fuse for direct blower power is a 50A ****-fuse. Manual has no listings of actual resistance values.
Erich777
TYF Newbie
So I took out the motor and put it on a laboratory grade variable power supply.
With a shot of WD40 on the bearings, mine draws 9.8 amps at 12 volts.
When I drop down to a slower speed of around 6 volts, my current drops to around 4 amps.
The odd thing, is that when I measure the current at the switch, low speed draws over 8 amps and the wires get quite hot! Jumping to the HI setting, I can hear the realay kick in, and I get about 0.2 amps at the switch.
So I still dont know if my motor is shot, or if I need a new resistor, or what....
With a shot of WD40 on the bearings, mine draws 9.8 amps at 12 volts.
When I drop down to a slower speed of around 6 volts, my current drops to around 4 amps.
The odd thing, is that when I measure the current at the switch, low speed draws over 8 amps and the wires get quite hot! Jumping to the HI setting, I can hear the realay kick in, and I get about 0.2 amps at the switch.
So I still dont know if my motor is shot, or if I need a new resistor, or what....
SunlitComet
OBS Jedi-Do Good
which wires specifically?
Erich777
TYF Newbie
So specifically:
Removing the front fan motor from the truck and using the two leads on the motor, I get about 9.5 amps at 12.5 VDC. at 6 volts, about 4 amps.
The REAR fan, (for comparison as I assume it has not been used as much) is clearly smaller. instead of removing the motor, I put an ammeter inline and found on low, it draws a little below 3 amps, on medium, about 6 amps, and on high a little less than 9 amps. (Voltage on the open circuit supplying the fan remained at around 12v regardless of the switch setting)
I also have some ammeter readings at the front fan, in dash switch. I could not find all five speeds, but the lowest I found had 8amps going through the switch, the medium speed I found had almost 10 amps, and the high (which runs a relay) puts only 0.15 amps through the switch.
So I am still wondering what to fix. at 8 amps, my jumper wire heats up to the point I can hardly grip it to remove it. Clearly too much power.
Perhaps its the blower motor resistor?
---------- Post added at 07:28 PM ---------- Previous post was at 07:23 PM ----------
Im also wondering about the pinout on the in dash fan speed switch.
I can jump the switch and get the fan to run on high, but I cant seem to get AC out of the front unit while using a jumper. (the rest of the control panel is plugged in)
I get good cold air out of the rear unit, and the compressor will come on for the rear unit, but still no cold out of the front system, nor will the compressor respond to the front AC control.
Removing the front fan motor from the truck and using the two leads on the motor, I get about 9.5 amps at 12.5 VDC. at 6 volts, about 4 amps.
The REAR fan, (for comparison as I assume it has not been used as much) is clearly smaller. instead of removing the motor, I put an ammeter inline and found on low, it draws a little below 3 amps, on medium, about 6 amps, and on high a little less than 9 amps. (Voltage on the open circuit supplying the fan remained at around 12v regardless of the switch setting)
I also have some ammeter readings at the front fan, in dash switch. I could not find all five speeds, but the lowest I found had 8amps going through the switch, the medium speed I found had almost 10 amps, and the high (which runs a relay) puts only 0.15 amps through the switch.
So I am still wondering what to fix. at 8 amps, my jumper wire heats up to the point I can hardly grip it to remove it. Clearly too much power.
Perhaps its the blower motor resistor?
---------- Post added at 07:28 PM ---------- Previous post was at 07:23 PM ----------
Im also wondering about the pinout on the in dash fan speed switch.
I can jump the switch and get the fan to run on high, but I cant seem to get AC out of the front unit while using a jumper. (the rest of the control panel is plugged in)
I get good cold air out of the rear unit, and the compressor will come on for the rear unit, but still no cold out of the front system, nor will the compressor respond to the front AC control.
SunlitComet
OBS Jedi-Do Good
On the high setting the switch is only powering a relay therefore hardly any current is drawn. You jumper also may not be of significant quality and gauge. the fan switch also disable disables the controller functions like a/c when in the off position.
So as it stands with the system put together no high speed fan just complete fan shut off. When you jumper the switch fan runs on high but does not run a/c controls. I am assuming that is with the switch still plugged in while jumping. It has got to be your fan switch. If switch is plugged in but you still jumper to activate hi speed the switch is still sending off voltage to disable the rest of system in front if the fan switch is off when your jumper it to activate high.
Is this helping or am I missing something.
The 1999 fan control circuit is below.
So as it stands with the system put together no high speed fan just complete fan shut off. When you jumper the switch fan runs on high but does not run a/c controls. I am assuming that is with the switch still plugged in while jumping. It has got to be your fan switch. If switch is plugged in but you still jumper to activate hi speed the switch is still sending off voltage to disable the rest of system in front if the fan switch is off when your jumper it to activate high.
Is this helping or am I missing something.
The 1999 fan control circuit is below.
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Erich777
TYF Newbie
EXCELLENT! Thanks for the schematic! Now I can work on this without reverse engineering the thing!
(Im going to put some keywords in here for future searchers)
1999 Tahoe fan switch schematic, or blower motor wiring diagram, or AC fan schematic, or fan speed control schematic.
I should probably do this in another thread, but do you have a schematic for the heater and freon hoses? (I only see refrigerant hoses going to the rear AC unit, and Im wondering if there never was heat going back there or if the rear heater core leaks and someone removed the lines)
(Im going to put some keywords in here for future searchers)
1999 Tahoe fan switch schematic, or blower motor wiring diagram, or AC fan schematic, or fan speed control schematic.
I should probably do this in another thread, but do you have a schematic for the heater and freon hoses? (I only see refrigerant hoses going to the rear AC unit, and Im wondering if there never was heat going back there or if the rear heater core leaks and someone removed the lines)
SunlitComet
OBS Jedi-Do Good
no hose routing charts, but if I understand correctly I believe heat went to rear in suburbans only. I keep missing that one and have not taking the time to gather some VIN numbers and run RPO codes to verify. Right click on image to view seperately and save the image from my server and rename it for your self. Would like to name them one day but never get to it. Also make them viewable with an HTML index with thumbnails.
Erich777
TYF Newbie
Thank you sunlit! I did save the image.
Even with a new switch, I still dont get front AC. Im still looking for a schematic that shows what valves and doors are connected to what wires. (or Ill just reverse engineer it)
I also have not fully diagnosed why the old switch melted, but since I now see the resistors are in series, Im wondering if one resistor has shorted to ground, creating a high current path capable of melting the switch. Ill have to dig back into the dash tomorrow and see what I find.
Even with a new switch, I still dont get front AC. Im still looking for a schematic that shows what valves and doors are connected to what wires. (or Ill just reverse engineer it)
I also have not fully diagnosed why the old switch melted, but since I now see the resistors are in series, Im wondering if one resistor has shorted to ground, creating a high current path capable of melting the switch. Ill have to dig back into the dash tomorrow and see what I find.
