heater/ac fan

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  #1  
Old 04-09-04, 08:03 PM
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heater/ac fan

i have a 1994 gmc safari van with a 6cyl 262 z 4.3l tbi, automatic transmission, 2 wheel drive.
the problem i am having is that my heater/ac fan will not work on high. it works on 1,2 and 3 but not on 4 (or high). any ideas?
thanks,
gary
 
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  #2  
Old 04-10-04, 08:15 AM
mike from nj
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some cars have a high speed fan relay, not sure if you do. a wiring diagram would reveal that.

also check your charging system, make sure it's at least 13.8 volts at idle(measured with a voltmeter at the battery), not the gauge on the dash.


also wait for more replies before replacing anything
 
  #3  
Old 04-13-04, 05:33 AM
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thanks mike, i will try this and see what happens. i thought that this was the problem but it is always good to hear from other brains.
thanks, gary
 
  #4  
Old 04-13-04, 11:52 AM
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there is a high speed relay...

...but all current for the blower fan flows thru it. if you take a test light or voltmeter and test at the relay here's what you find. there is a heavy purple wire...this goes from the relay to the fan motor and will have voltage present on every speed except high since your high isn't working. there is a heavy red wire on the relay also and this is the current supply for the high setting. there should be voltage available on this wire all the time. no voltage here means the fuse link may be bad or a bad connection at the junction block where the red wire gets it's current from.

next...at the relay there is an orange wire and this wire should be "hot" when the blower is set to high. no voltage = a bad switch in the dash. voltage here should cause the relay to switch on (you should feel and hear it click) and this in turn connects the red and purple wires together inside the relay (the net effect here is connecting the blower motor directly to the battery)so...

test light on red = voltage all the time

test light on orange = voltage with switch on high

since you blower works on all other speeds, it has to be either the power feed to the relay (fuse link), the switch...or the relay.

good luck....
 
  #5  
Old 04-15-04, 05:16 AM
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thanks carguyinva. i will try this and report asap.
gary
 
  #6  
Old 04-15-04, 08:25 AM
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hey carguyinva, here is what i found out. for the sake of explanation i will call the fan speeds 1,2,3, and 4. with 1 as low and 4 being high.
i checked fan speed 1 and got voltage on red blue and purple. and i also got the same voltage on 2 and 3 as i did on 1.
but when i turned the fan switch to 4 or high i only got voltage on the blue wire and on the orange wire and not on the red wire.
so what do i do next. fuse link, resistor, switch or relay.
thanks,
gary
 
  #7  
Old 04-15-04, 12:27 PM
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sounds like...

...the fuse link burnt up...in this case you may also have a blower motor failing and drawing too much current as the fuse link is designed to burn in that situation (it works like a fuse but doesn't blow as fast)...follow that red wire back to where it connects to the junction block and tug on the wire...if it stretches and breaks, it was blown. if it doesn't, check for voltage available at the junction block...it has a wire that runs from it to the battery and perhaps there is a bad connection somewhere. you've zeroed in on the problem now just backtrack that red wire to find the cause of the open circuit.

ps...the only sure way to tell if your blower motor is failing is to have the amperage draw of the motor tested...
 
  #8  
Old 04-15-04, 05:34 PM
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hey carguyinva, sorry but i gave you some bad information on my last post about voltage on which wires. fan settings 1,2 and 3 have voltage on only 2 wires being blue and purple. setting 4 has voltage on only 2 wires blue and orange. the red wire is not hot at all on any setting. the reason for the error was the first time i used a digital volt meter and picked up voltage on the red wire in setting 1,2 and 3. so i double checked later after my post with a test light and found no voltage on the red wire. so i guess what you are saying is that i need to trace out the red wire and try to find a fuse link. oh buy the way all of the fuses on the fuse block are ok. i have a book but it doesn't show where the fuse link is. i'll just look around and see it couldn't be that hard because it's not that far from the relay to the fuse block. i had the blower motor replaced last year at pep boys maybe they put a cheap motor on it. well anyway thanks for all of your help and i will dig a little deeper until i find the problem.
thanks,
gary
 
  #9  
Old 04-15-04, 06:36 PM
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Those links will either be found at a junction stud on the firewall or coming off the starter. Try pulling on them individually and the bad one will stretch because the wire is melted in two inside of the insulation.
 
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