Home » Public Forums » GMCnet » [GMCnet] heater fan
| [GMCnet] heater fan [message #263048] |
Mon, 29 September 2014 23:38  |
Brian Waddell
Messages: 409
Registered: March 2010
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On my 77 gmc with a 455.......After reading the manual, I still have guestions about how the heater fan should work. Mine has the heater fan with no off position ...only low. However...I have detached the wire for the low or continuous on from the drivers(left side) of heater box. Then I bypassed the time delay relay and connected blower motor wire directly to blower relay. My manual says this is a four speed fan . I am assuming they do not count the fan being off as a speed as in the 77 supplement book the fan should always be on with the key. Now with my modifications and the engine not running the setting on heater I have ....off....first indent low ....second indent med ....third indent the same as second...I have traced wires and checked for continuity....I am thinking the fusible link is a small cyl shaped object from the red wire with white stripe coming from theblower relay...ther is continuity on each side..Where else has anyone found a fusible link?. My fan has the
se speeds with the engine running on the heater selection. With max air selection I have no fan in the highest speed with engine running...When I reread this I know it sounds confusing.. Ok then...Can someone who has the same no off position fan tell me what fan speed they have? Can they be described as low 1 2 3 that would mean a 4 speed fan....hope someone can make sence out of this ramble.....maybe emory....thanks....brian 77 ele
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| Re: [GMCnet] heater fan [message #263052 is a reply to message #263048] |
Tue, 30 September 2014 00:24  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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It is a single speed motor look at it there is only one wire on the motor. The multi speed is obtained with voltage dropping resistors. High speed is obtained with a separate relay that connects to the alternator output rather then the ignition switch so the motor has the highest voltage possible when it is on high. If you don't have a wiring diagram there is a free download available .
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] heater fan [message #263059 is a reply to message #263048] |
Tue, 30 September 2014 08:50 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I don't have the correct simple mod tip as I would never do that mod. GM engineers did the always on feature to keep some positve fresh air flow into the cabin to keep CO from creaping in the rear windows etc. That said the resistor diagram is not as simple as one would think. The powor loops to and from the dash switch to the resistor pack to create the right choice of resistors for the sppropriate fan speed drop. Appaenty the wire you have pulled is not getting signal to the Hi relay on max.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] heater fan [message #263069 is a reply to message #263048] |
Tue, 30 September 2014 12:05 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
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Brian Waddell wrote on Mon, 29 September 2014 21:38...and the engine not running...
My interpretation is that when on max speed the blower is fed directly from the alternator, so it is getting around 14 volts. With the engine off as you said, you won't have this voltage. What happens if you do the same test with the engine running?
Edit: Oops, just noticed in your post that you have nothing on high with the engine running.
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
[Updated on: Tue, 30 September 2014 12:07] Report message to a moderator |
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| Re: [GMCnet] heater fan [message #263074 is a reply to message #263073] |
Tue, 30 September 2014 14:09 |
emerystora
Messages: 4442
Registered: January 2004
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Your fan has the same number of speeds on all functions. But, unless you have the engine running you will not have the hugest speed. That is controlled by the blower motor relay which switches over to power directly from the alternator which is higher voltage so the fan will run faster.
Emery Stora
> On Sep 30, 2014, at 1:18 PM, Brian Waddell wrote:
>
> Oh boy.....I am going to have to rethink all this.....A simple thing that I would like to know is:
> On a 77 motorhome ...engine off...all original with the always on fan...how many fan speeds are there as you move the control through its functions from defrost back through max air and then to off? How many fan speeds in each position?
> Now...on the same mh with engine running how many fan speeds in each position?
>
>> Date: Tue, 30 Sep 2014 11:05:42 -0600
>> To: gmclist@temp.gmcnet.org
>> From: dao@oarsllc.com
>> Subject: Re: [GMCnet] heater fan
>>
>> Brian Waddell wrote on Mon, 29 September 2014 21:38
>>> ...and the engine not running...
>>
>>
>> My interpretation is that when on max speed the blower is fed directly from the alternator, so it is getting around 14 volts. With the engine off as
>> you said, you won't have this voltage. What happens if you do the same test with the engine running?
>>
>> --
>> 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to
>> us."
>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263086 is a reply to message #263074] |
Tue, 30 September 2014 20:34 |
Brian Waddell
Messages: 409
Registered: March 2010
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So ...If that is the case...with engine off...,.I should not get fan at any function when the blower is set to highest speed
> From: emerystora@mac.com
> Date: Tue, 30 Sep 2014 14:09:31 -0500
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] heater fan
>
> Your fan has the same number of speeds on all functions. But, unless you have the engine running you will not have the hugest speed. That is controlled by the blower motor relay which switches over to power directly from the alternator which is higher voltage so the fan will run faster.
>
> Emery Stora
>
>> On Sep 30, 2014, at 1:18 PM, Brian Waddell wrote:
>>
>> Oh boy.....I am going to have to rethink all this.....A simple thing that I would like to know is:
>> On a 77 motorhome ...engine off...all original with the always on fan...how many fan speeds are there as you move the control through its functions from defrost back through max air and then to off? How many fan speeds in each position?
>> Now...on the same mh with engine running how many fan speeds in each position?
>>
>>> Date: Tue, 30 Sep 2014 11:05:42 -0600
>>> To: gmclist@temp.gmcnet.org
>>> From: dao@oarsllc.com
>>> Subject: Re: [GMCnet] heater fan
>>>
>>> Brian Waddell wrote on Mon, 29 September 2014 21:38
>>>> ...and the engine not running...
>>>
>>>
>>> My interpretation is that when on max speed the blower is fed directly from the alternator, so it is getting around 14 volts. With the engine off as
>>> you said, you won't have this voltage. What happens if you do the same test with the engine running?
>>>
>>> --
>>> 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to
>>> us."
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
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>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263087 is a reply to message #263086] |
Tue, 30 September 2014 20:46 |
emerystora
Messages: 4442
Registered: January 2004
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I will have to go to my GMC to check but I don't think that I have any fan speeds at all unless the engine is running. However, the highest speed is when the A/C is set to MAX. That then allows the relay to get alternator voltage to the fan.
I will check my system and get back to you.
Emery Stora
On Sep 30, 2014, at 8:34 PM, Brian Waddell wrote:
> So ...If that is the case...with engine off...,.I should not get fan at any function when the blower is set to highest speed
>
>
>> From: emerystora@mac.com
>> Date: Tue, 30 Sep 2014 14:09:31 -0500
>> To: gmclist@temp.gmcnet.org
>> Subject: Re: [GMCnet] heater fan
>>
>> Your fan has the same number of speeds on all functions. But, unless you have the engine running you will not have the hugest speed. That is controlled by the blower motor relay which switches over to power directly from the alternator which is higher voltage so the fan will run faster.
>>
>> Emery Stora
>>
>>> On Sep 30, 2014, at 1:18 PM, Brian Waddell wrote:
>>>
>>> Oh boy.....I am going to have to rethink all this.....A simple thing that I would like to know is:
>>> On a 77 motorhome ...engine off...all original with the always on fan...how many fan speeds are there as you move the control through its functions from defrost back through max air and then to off? How many fan speeds in each position?
>>> Now...on the same mh with engine running how many fan speeds in each position?
>>>
>>>> Date: Tue, 30 Sep 2014 11:05:42 -0600
>>>> To: gmclist@temp.gmcnet.org
>>>> From: dao@oarsllc.com
>>>> Subject: Re: [GMCnet] heater fan
>>>>
>>>> Brian Waddell wrote on Mon, 29 September 2014 21:38
>>>> > ...and the engine not running...
>>>>
>>>>
>>>> My interpretation is that when on max speed the blower is fed directly from the alternator, so it is getting around 14 volts. With the engine off as
>>>> you said, you won't have this voltage. What happens if you do the same test with the engine running?
>>>>
>>>> --
>>>> 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to
>>>> us."
>>>> _______________________________________________
>>>> GMCnet mailing list
>>>> Unsubscribe or Change List Options:
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>>>
>>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263088 is a reply to message #263087] |
Tue, 30 September 2014 21:37 |
Brian Waddell
Messages: 409
Registered: March 2010
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reason I ask is that I got fan speeds ....but I am having a hard time determining if I am getting that max fan speed direct from alt...when in max ac position .or am I getting the high med fan speed.77 ele 455
> From: emerystora@mac.com
> Date: Tue, 30 Sep 2014 20:46:59 -0500
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] heater fan
>
> I will have to go to my GMC to check but I don't think that I have any fan speeds at all unless the engine is running. However, the highest speed is when the A/C is set to MAX. That then allows the relay to get alternator voltage to the fan.
>
> I will check my system and get back to you.
>
> Emery Stora
>
> On Sep 30, 2014, at 8:34 PM, Brian Waddell wrote:
>
>> So ...If that is the case...with engine off...,.I should not get fan at any function when the blower is set to highest speed
>>
>>
>>> From: emerystora@mac.com
>>> Date: Tue, 30 Sep 2014 14:09:31 -0500
>>> To: gmclist@temp.gmcnet.org
>>> Subject: Re: [GMCnet] heater fan
>>>
>>> Your fan has the same number of speeds on all functions. But, unless you have the engine running you will not have the hugest speed. That is controlled by the blower motor relay which switches over to power directly from the alternator which is higher voltage so the fan will run faster.
>>>
>>> Emery Stora
>>>
>>>> On Sep 30, 2014, at 1:18 PM, Brian Waddell wrote:
>>>>
>>>> Oh boy.....I am going to have to rethink all this.....A simple thing that I would like to know is:
>>>> On a 77 motorhome ...engine off...all original with the always on fan...how many fan speeds are there as you move the control through its functions from defrost back through max air and then to off? How many fan speeds in each position?
>>>> Now...on the same mh with engine running how many fan speeds in each position?
>>>>
>>>> > Date: Tue, 30 Sep 2014 11:05:42 -0600
>>>> > To: gmclist@temp.gmcnet.org
>>>> > From: dao@oarsllc.com
>>>> > Subject: Re: [GMCnet] heater fan
>>>> >
>>>> > Brian Waddell wrote on Mon, 29 September 2014 21:38
>>>> >> ...and the engine not running...
>>>> >
>>>> >
>>>> > My interpretation is that when on max speed the blower is fed directly from the alternator, so it is getting around 14 volts. With the engine off as
>>>> > you said, you won't have this voltage. What happens if you do the same test with the engine running?
>>>> >
>>>> > --
>>>> > 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to
>>>> > us."
>>>> > _______________________________________________
>>>> > GMCnet mailing list
>>>> > Unsubscribe or Change List Options:
>>>> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>>
>>>> _______________________________________________
>>>> GMCnet mailing list
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>>> _______________________________________________
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>>
>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263090 is a reply to message #263088] |
Tue, 30 September 2014 21:49 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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The cotton pickin' thing makes so much noise on WFO I don't even turn mine
there.
Jim Hupy (in Redding Ca. on the way to GMCWS tomorrow)
78 GMC ROYALE 403
On Sep 30, 2014 7:37 PM, "Brian Waddell" wrote:
> reason I ask is that I got fan speeds ....but I am having a hard time
> determining if I am getting that max fan speed direct from alt...when in
> max ac position .or am I getting the high med fan speed.77 ele 455
>
>
>> From: emerystora@mac.com
>> Date: Tue, 30 Sep 2014 20:46:59 -0500
>> To: gmclist@temp.gmcnet.org
>> Subject: Re: [GMCnet] heater fan
>>
>> I will have to go to my GMC to check but I don't think that I have any
> fan speeds at all unless the engine is running. However, the highest speed
> is when the A/C is set to MAX. That then allows the relay to get alternator
> voltage to the fan.
>>
>> I will check my system and get back to you.
>>
>> Emery Stora
>>
>> On Sep 30, 2014, at 8:34 PM, Brian Waddell
> wrote:
>>
>>> So ...If that is the case...with engine off...,.I should not get fan
> at any function when the blower is set to highest speed
>>>
>>>
>>>> From: emerystora@mac.com
>>>> Date: Tue, 30 Sep 2014 14:09:31 -0500
>>>> To: gmclist@temp.gmcnet.org
>>>> Subject: Re: [GMCnet] heater fan
>>>>
>>>> Your fan has the same number of speeds on all functions. But, unless
> you have the engine running you will not have the hugest speed. That is
> controlled by the blower motor relay which switches over to power directly
> from the alternator which is higher voltage so the fan will run faster.
>>>>
>>>> Emery Stora
>>>>
>>>> > On Sep 30, 2014, at 1:18 PM, Brian Waddell
> wrote:
>>>> >
>>>> > Oh boy.....I am going to have to rethink all this.....A simple thing
> that I would like to know is:
>>>> > On a 77 motorhome ...engine off...all original with the always on
> fan...how many fan speeds are there as you move the control through its
> functions from defrost back through max air and then to off? How many fan
> speeds in each position?
>>>> > Now...on the same mh with engine running how many fan speeds in each
> position?
>>>> >
>>>> >> Date: Tue, 30 Sep 2014 11:05:42 -0600
>>>> >> To: gmclist@temp.gmcnet.org
>>>> >> From: dao@oarsllc.com
>>>> >> Subject: Re: [GMCnet] heater fan
>>>> >>
>>>> >> Brian Waddell wrote on Mon, 29 September 2014 21:38
>>>> >>> ...and the engine not running...
>>>> >>
>>>> >>
>>>> >> My interpretation is that when on max speed the blower is fed
> directly from the alternator, so it is getting around 14 volts. With the
> engine off as
>>>> >> you said, you won't have this voltage. What happens if you do the
> same test with the engine running?
>>>> >>
>>>> >> --
>>>> >> 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop
> all evil in the world, but I know that how we treat one another is entirely
> up to
>>>> >> us."
>>>> >> _______________________________________________
>>>> >> GMCnet mailing list
>>>> >> Unsubscribe or Change List Options:
>>>> >> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>> >
>>>> > _______________________________________________
>>>> > GMCnet mailing list
>>>> > Unsubscribe or Change List Options:
>>>> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>> _______________________________________________
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>>>
>>> _______________________________________________
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>>
>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263094 is a reply to message #263090] |
Tue, 30 September 2014 22:43 |
Brian Waddell
Messages: 409
Registered: March 2010
Karma: -4
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Senior Member |
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That is interesting....mine does not make much noise on high...it is blowing on the high setting with eng running but I do not think this is the highest speed direct from alt and have not yet determined how to test this out....thanks...Brian ps Just a short drive west of you when I give up on steering issues and need the issue fixed once and for all........wpg mb
> Date: Tue, 30 Sep 2014 19:49:14 -0700
> From: jamesh1296@gmail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] heater fan
>
> The cotton pickin' thing makes so much noise on WFO I don't even turn mine
> there.
> Jim Hupy (in Redding Ca. on the way to GMCWS tomorrow)
> 78 GMC ROYALE 403
> On Sep 30, 2014 7:37 PM, "Brian Waddell" wrote:
>
>> reason I ask is that I got fan speeds ....but I am having a hard time
>> determining if I am getting that max fan speed direct from alt...when in
>> max ac position .or am I getting the high med fan speed.77 ele 455
>>
>>
>>> From: emerystora@mac.com
>>> Date: Tue, 30 Sep 2014 20:46:59 -0500
>>> To: gmclist@temp.gmcnet.org
>>> Subject: Re: [GMCnet] heater fan
>>>
>>> I will have to go to my GMC to check but I don't think that I have any
>> fan speeds at all unless the engine is running. However, the highest speed
>> is when the A/C is set to MAX. That then allows the relay to get alternator
>> voltage to the fan.
>>>
>>> I will check my system and get back to you.
>>>
>>> Emery Stora
>>>
>>> On Sep 30, 2014, at 8:34 PM, Brian Waddell
>> wrote:
>>>
>>>> So ...If that is the case...with engine off...,.I should not get fan
>> at any function when the blower is set to highest speed
>>>>
>>>>
>>>> > From: emerystora@mac.com
>>>> > Date: Tue, 30 Sep 2014 14:09:31 -0500
>>>> > To: gmclist@temp.gmcnet.org
>>>> > Subject: Re: [GMCnet] heater fan
>>>> >
>>>> > Your fan has the same number of speeds on all functions. But, unless
>> you have the engine running you will not have the hugest speed. That is
>> controlled by the blower motor relay which switches over to power directly
>> from the alternator which is higher voltage so the fan will run faster.
>>>> >
>>>> > Emery Stora
>>>> >
>>>> >> On Sep 30, 2014, at 1:18 PM, Brian Waddell
>> wrote:
>>>> >>
>>>> >> Oh boy.....I am going to have to rethink all this.....A simple thing
>> that I would like to know is:
>>>> >> On a 77 motorhome ...engine off...all original with the always on
>> fan...how many fan speeds are there as you move the control through its
>> functions from defrost back through max air and then to off? How many fan
>> speeds in each position?
>>>> >> Now...on the same mh with engine running how many fan speeds in each
>> position?
>>>> >>
>>>> >>> Date: Tue, 30 Sep 2014 11:05:42 -0600
>>>> >>> To: gmclist@temp.gmcnet.org
>>>> >>> From: dao@oarsllc.com
>>>> >>> Subject: Re: [GMCnet] heater fan
>>>> >>>
>>>> >>> Brian Waddell wrote on Mon, 29 September 2014 21:38
>>>> >>>> ...and the engine not running...
>>>> >>>
>>>> >>>
>>>> >>> My interpretation is that when on max speed the blower is fed
>> directly from the alternator, so it is getting around 14 volts. With the
>> engine off as
>>>> >>> you said, you won't have this voltage. What happens if you do the
>> same test with the engine running?
>>>> >>>
>>>> >>> --
>>>> >>> 1976 Royale "Twinkie II" Lynnwood WA - "We may not be able to stop
>> all evil in the world, but I know that how we treat one another is entirely
>> up to
>>>> >>> us."
>>>> >>> _______________________________________________
>>>> >>> GMCnet mailing list
>>>> >>> Unsubscribe or Change List Options:
>>>> >>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>> >>
>>>> >> _______________________________________________
>>>> >> GMCnet mailing list
>>>> >> Unsubscribe or Change List Options:
>>>> >> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>> > _______________________________________________
>>>> > GMCnet mailing list
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>>>> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>>>
>>>> _______________________________________________
>>>> GMCnet mailing list
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>>>
>>> _______________________________________________
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>>
>> _______________________________________________
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| Re: [GMCnet] heater fan [message #263096 is a reply to message #263094] |
Wed, 01 October 2014 03:00 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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If you have the fan working on all 4 speeds as you expect, then disconnect the wire going from the fan relay to the isolator. Check to see if fan speed 4 still works with the engine running. If it does not work, then you are powering the fan in speed 4 from the alternator. If it does work, then you have a fan relay problem.
Fan speed 1 operation has nothing to do with fan speed 4 operation. Lots of us have modified fan speed 1 to be off rather than slow as designed. This mod has nothing to do with fan speed 4 operation.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] heater fan [message #263101 is a reply to message #263048] |
Wed, 01 October 2014 08:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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1 2 3 are thru the resistor network. Power from Ign. 4 and max are from the relay via the alternator. However the signal to the relay is from ign thru the dash fan switch. The Max position grabs the 4 contact from the fan switch to the relay as well as closes compressor contacts and sends vac to the rec door motor. Put it back to stock and then diagnose what is working/ not working. There are 4 speeds but 2 is not markedly much faster than 1. Try cleaning and exercising the connectors at the resistor and Hi relay. These are famous for oxidation and melt down.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] heater fan [message #263106 is a reply to message #263101] |
Wed, 01 October 2014 11:56 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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JohnL455 wrote on Wed, 01 October 2014 08:371 2 3 are thru the resistor network. Power from Ign. 4 and max are from the relay via the alternator. However the signal to the relay is from ign thru the dash fan switch. The Max position grabs the 4 contact from the fan switch to the relay as well as closes compressor contacts and sends vac to the rec door motor. Put it back to stock and then diagnose what is working/ not working. There are 4 speeds but 2 is not markedly much faster than 1. Try cleaning and exercising the connectors at the resistor and Hi relay. These are famous for oxidation and melt down. I looked at the schematic for the 77 model and figured out the difference in the dash control from the 73/74 models. GM added a resistor to the resistor pack (probably the same value as the original Lo) and ran a tan wire from the old Lo blade to the resistor pack pin that used to be the yellow (Lo) resistor. They moved the yellow wire on the switch to a junction to the brown wire from the Acc buss and terminated it on the new resistor in the resistor pack. They relabeled the switch positions on the control from Off, Lo, Med, High, to Lo, MedLo, Med, High. That way the tan wire replaced the yellow wire for Lo (now called MedLo) and the yellow wire became the power for the "always on" function of the control (previously the "Off" position of the dash fan switch).
They would have saved a lot of people a lot of head scratching if they had left the yellow wire alone and ran the tan wire from the brown wire junction to the new resistor in the resistor pack to achieve their "always on" fan function. Then people could just disconnect the tan wire to restore the "Off" function and the rest of the harness would have been the same for all model years.
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