'94 Astro Blower Motor

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  #1  
Old 08-24-05, 12:27 PM
Opto
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'94 Astro Blower Motor

The blower motor on my 1994 Chevy Astro Van does not work. I connected a 12v lead directly to the blower’s positive terminal and the blower turned on so I’m thinking it is either the relay or the dash control. Is there a way to test these two items to determine which is bad? Is there anything else that could be wrong?
 
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  #2  
Old 08-24-05, 01:48 PM
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9 times out of ten it is the blower resistor box

could be switch or relay.

you need to use a multimeter and test for continuity
 
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Old 08-24-05, 02:30 PM
Opto
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Sorry, but I don't know what you mean by "blower resistor box" What is it and where is it? Is this the part I should be testing for continuity? (I do have a multimeter).
 
  #4  
Old 08-24-05, 02:54 PM
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when you turn the knob to select a speed al your are doing is swithing in different valued resistors in series with the blower motor so that less voltage is at the motor, which causes it spin slower. these tend to burn up

sorry but i don't get indepth with how to do electrical work on cars, i point you in the direction you need to go but i don't spell it all out. if you want procedures on how to do what i say they are out there on the net. just remember electrical stuff in cars is 90% of the time technology and circuits from the 70's even in brand new cars. well some 2005 models have technology from the late 80's maybe early 90's if you are lucky. thats why i do not explain how to check the circuits. all you are looking for is opens. test the switch, check the resistor block, check the relay, fuse, then lastly you would have to check the wiring for continuity
 
  #5  
Old 08-24-05, 03:05 PM
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Check the blower motor fuse 1st.
 
  #6  
Old 08-24-05, 03:48 PM
Opto
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shottys
if you want procedures on how to do what i say they are out there on the net
This (the DoItYourself Form) is "out there on the net". It's why I come here; to get answers spelled out when I can't figure it out myself.

My blower gradually stopped working. First the high speed went out; then medium became erratic and finally it all went south. Judging from these sysmptoms it seems like the "resistor box" is the most likely candidate.

While I can find the switch in the dash and the relay on the firewall, I can't find any resistors. Maybe we could play 20 questions: are they inside the van?


jeff

The fuse (labeled "heater" in the fuse box located inside under the dash) is OK. Howerver, according to my Haines manual there is also a 30A fuse in the engine compartment but I can't find that one either. There is supposed to be a continuous 12v supply to one terminal of the relay, but it only tests at 6v. However, if that fuse was blown it shouldn't read anything.

electrical work has always been a bytch for me. Give me CV joints and brakes any time...
 
  #7  
Old 08-24-05, 04:45 PM
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Originally Posted by Opto

There is supposed to be a continuous 12v supply to one terminal of the relay, but it only tests at 6v. However, if that fuse was blown it shouldn't read anything.
schmuck

You have a bad connection from the 12V line trace it down and find where the voltage drops to 6V.

unless you have a bad ground on the other multimeter lead
 
  #8  
Old 08-24-05, 06:21 PM
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When you are measuring 6V, is the blower switch on and set to some position other than high? If so, that could be the resistor doing its job of dropping the voltage. Measure the voltage without the blower switch being on if you haven't done so and with it being on at the different speeds and see if you notice any differences in the measurements.

I don't know the exact location of it on your van but the blower resistor should be mounted on the evaporater housing under the passenger side dash or possibly even on the fan. You won't see the resistors, but a wire harness that connects to the module. The resistors get cooled by the air from the blower motor. They get very hot when they are dropping voltage to the motor except on high, when the motor gets full voltage. For this reason, if you get a new resistor stack, its best not to try it out before you install it, or test it very briefly for a second or 2 with it not installed. Your Haynes manual probably has a picture of it and where it's located.

Also make sure the connections at the relay, resistor, and blower are good and clean.
 
  #9  
Old 08-24-05, 06:30 PM
protouser
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Wink funny

That was good 20 questions lol is it in the van lol. all in good fun guys all in good fun
 
  #10  
Old 08-25-05, 03:35 PM
Opto
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jeff:

The 6v reading is at the relay, done on the red wire that is supposed to be 12v continuous.

All connections, including the relay (I opened it up) are clean, without any signs of corrosion. I did a continuity test on the dash switch and it is functioning properly. Voltages at the relay are the same going in and coming out so the contacts are good.

Funny thing but I check the volts at the relay for the other positions (Lo, M1, M2) and they all read 12v. I thought: "If I've got 12v the blower should work". I hooked it up and it did work including changing speeds. But still nothing on High.

The Haynes manual is a little vague. There is no picture or even any mention of the resistor pack. And the wiring diagram makes it look like the relay and resistor pack are one item. (apparently they are on later models)

Thanks for the location of the resistor pack. I'll start poking around the interior passenger side.
 
  #11  
Old 08-25-05, 07:52 PM
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So when the blower speed is on high, you're reading 6V, otherwise 12V? There might be some resistance in the circuit that won't allow enough current to run the blower on high. Could be a bad or lose connection somewhere or a bad wire, relay, or switch.

As mentioned before, most blower speed problems are the result of a bad resistor pack so that could be the problem, although mostly its the high speed setting that works and the others that won't with a resistor pack problem.

If you have another relay in the relay box that is the same, swap them and see if that fixes it.
 
  #12  
Old 08-25-05, 07:59 PM
shottys2
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the voltage he checked is from the battery he had the relay unplugged.

also if you open the resistor circuit and measure the votlage without the other end of the circuit being grounded it will not measure lower i don't care where you measure for voltage the circuit must be 100% in tack to measure the drop. there has to be a path for current to flow in order to measure a voltage drop.

You need 12V at the wire from the battery to the relay.

So if the blower motor is not passing any current he will never read a correct voltage.

V=IR if I is equal to 0 you have no current flow and there for no voltage drop. all you have is a resistor that is sitting at a 12V potential no matter how you measure it.

you must have a complete circuit in order to correctly measure voltage drops
 
  #13  
Old 08-26-05, 09:14 AM
Opto
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I’m beginning to suspect that it is the relay that has been causing the intermittent problem on the lower speeds. And shottys2 is right about taking the voltage readings under load. When the blower kicked in on the M2 speed I took another reading and it had dropped to 10v. So I believe that the resistor pack is still functioning correctly.

Now I just have to find out why the red lead is at half mast. It disappears in a loom and it’s been a pain trying to find where it emerges.
 
  #14  
Old 08-26-05, 04:53 PM
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If your motor is not functioning on high then it is definately NOT the blower motor resistor. The resistor only affects the lower fan speeds. When you measured the 12v to 10v voltage drop was the engine running? The resistor is located in the top of the heater box under the hood... but you dont need to mess with it because there isnt likely anything wrong with it. I would start with a wiring diagram and trace the wires from the blower motor back to the fuse and see where the problem actually is.
Good luck.
Hope this helps ya,
Billy
 
  #15  
Old 08-26-05, 05:34 PM
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There is a good chance that there is a different relay and fuse for the high speed setting then the lower speeds You did mention a different relay location at the resistor from the Haynes manual. Also you may have to look further for that 30A fuse as there might be 2 fuses, one for a high speed relay, one for a lower speeds relay. Check your owners manual, if you have it, for all fuses and relays for the blower motor. Or check your Haynes manual, or a Chiltons manual. I don't know what the heater fuse is, if it's related to the blower or not.
 
  #16  
Old 08-28-05, 08:54 AM
Opto
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I finally traced the 12v “red” line from the relay. It has a fusible link (not a fuse as shown in the Haynes manual), and it is in a connector with 4 other “red” lines with fusible links that plug into the firewall on the drives side behind the battery.

After doing a continuity test to find the correct line, I checked the voltage coming out of the firewall. It was 12v. So I plugged the lines back in and checked the voltage at the relay and it was 12v. Apparently there was some corrosion on the terminals that was dropping the voltage. A little terminal cleaning and the high speed is working.

I also did some cleaning on the relay and all the other speeds are working as well. But I will be replacing the relay soon.

And I finally found the resistor pack! I also cleaned those terminals.

Thanks for all the guidance.
 
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