| [GMCnet] Resistor Pack for blower motor -- shorted? [message #277775] |
Wed, 13 May 2015 11:59  |
Daniel DeLuca
Messages: 120
Registered: June 2014
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Hello,
My fan blower once again lost max over the winter. I played around with some of the wires, blew a fuse. I found the short and replaced the fuse, when I replaced the fuse I no longer had any fan speeds. I do not have any voltage coming from the blue wire going from resistor pack to the relay. I have checked the wire and I have continuity from the resistor pack to the relay. I have checked voltage going into the resistor pack and have 12 volts at several wires. Is the resistor pack replaceable or repairable? Any other places of failure I might be missing?
Dan
78 Eleganza II
New Jersey
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277784 is a reply to message #277775] |
Wed, 13 May 2015 13:50  |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Are the wires at the relay connector making contact?
Mine were frayed and I had to re-solder them.
I also replaced the relay and the fan motor.
Maybe a rodent has built a nest in the fan motor....
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277785 is a reply to message #277775] |
Wed, 13 May 2015 15:01 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Daniel DeLuca wrote on Wed, 13 May 2015 09:59Hello,
My fan blower once again lost max over the winter. I played around with some of the wires, blew a fuse. I found the short and replaced the fuse, when I replaced the fuse I no longer had any fan speeds. I do not have any voltage coming from the blue wire going from resistor pack to the relay. I have checked the wire and I have continuity from the resistor pack to the relay. I have checked voltage going into the resistor pack and have 12 volts at several wires. Is the resistor pack replaceable or repairable? Any other places of failure I might be missing?
Dan
Sounds like you have more than one problem. But, to the loosing high speed, I believe the high speed is supplied by a separate wire that is linked to the alternator so the fan motor gets full power when running on high. Hopefully some of the experts can tell you how that wiring is done.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277789 is a reply to message #277775] |
Wed, 13 May 2015 16:09 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Sir, the ground wire is famous for getting loose.
http://www.gmcmhphotos.com/photos/member-galleries/p42831-dsc03822-a.html
Daniel DeLuca wrote on Wed, 13 May 2015 12:59Hello,
My fan blower once again lost max over the winter. I played around with some of the wires, blew a fuse. I found the short and replaced the fuse, when I replaced the fuse I no longer had any fan speeds. I do not have any voltage coming from the blue wire going from resistor pack to the relay. I have checked the wire and I have continuity from the resistor pack to the relay. I have checked voltage going into the resistor pack and have 12 volts at several wires. Is the resistor pack replaceable or repairable? Any other places of failure I might be missing?
Dan
78 Eleganza II
New Jersey
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C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277792 is a reply to message #277775] |
Wed, 13 May 2015 16:39 |
Dan
Messages: 99
Registered: August 2014
Location: Allentown, NJ
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You are correct I have two problems. The relay is bad and the resistor pack is bad. I have already bypassed the delay relay. I pulled the resistor pack, I am not sure what I expected but its pretty clear where the problem is
Here is a link to the picture
http://imgur.com/zTsxntY
I already have a spare relay. Does anyone have a part number or source for a relay pack?
Dan
78' Eleganza
New Jersey
Dan DeLuca
1978 Eleganza II (http://imgur.com/gallery/YFHhK)
Parked at Evil Monkey Farm in
Allentown, New Jersey
[Updated on: Wed, 13 May 2015 16:40] Report message to a moderator |
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277793 is a reply to message #277788] |
Wed, 13 May 2015 16:41 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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The fan relay coil is energized from the fan control switch.
Do you have +12 volts on one side of the coil and -12 volts (ground) on the other side of the coil?
With the key turned on, when you move the fan switch between position 3 and 4 can you feel (or hear) the relay click?
If the relay coil is energizing with the fan switch in its highest speed, then check the relay operating contact for +12 volts. The operating point of the contacts goes to the Fan motor.
The relay Normally Open point is wired to the center position of the isolator. This means the Normally Open point will only have power on it when the engine is running and power is being supplied by the the alternator. Do you have +12 volts on the N/O contact when the engine is running?
If the above are all OK then you should see +12 volts on the operating point of the relay and at the fan motor WHEN THE ENGINE IS RUNNING.
If you have +12 at the fan motor connection, check the ground wire going to the fan motor. The fan motor gets its ground from the wire and not from it's mounting.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277809 is a reply to message #277775] |
Wed, 13 May 2015 22:05 |
Dan
Messages: 99
Registered: August 2014
Location: Allentown, NJ
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Thanks Ken,
We are all troubleshooted now. My resistor pack blew. Wouldn't happen to know a part number or a cross reference vehicle for the resister pack on a 78?
Dan
Dan DeLuca
1978 Eleganza II (http://imgur.com/gallery/YFHhK)
Parked at Evil Monkey Farm in
Allentown, New Jersey
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277811 is a reply to message #277793] |
Wed, 13 May 2015 22:06 |
Daniel Starks
Messages: 20
Registered: April 2015
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It looks to me like the fan relay is energized when either, the fan
switch is in high, or the "Htr & A/C control" switch is in A/C or Def.
Therefore, if you want to hear the relay click, you would need to set
the control to either vent or htr. Then, moving the fan switch between
position 3 and 4 should make the relay click. A question, what useful
purpose does the delay relay have?
Daniel
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Ken
Burton
Sent: Wednesday, May 13, 2015 3:41 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Resistor Pack for blower motor -- shorted?
The fan relay coil is energized from the fan control switch.
Do you have +12 volts on one side of the coil and -12 volts (ground) on
the other side of the coil?
With the key turned on, when you move the fan switch between position 3
and 4 can you feel (or hear) the relay click?
If the relay coil is energizing with the fan switch in its highest
speed, then check the relay operating contact for +12 volts. The
operating point of the contacts goes to the Fan motor.
The relay Normally Open point is wired to the center position of the
isolator. This means the Normally Open point will only have power on it
when the
engine is running and power is being supplied by the the alternator.
Do you have +12 volts on the N/O contact when the engine is running?
If the above are all OK then you should see +12 volts on the operating
point of the relay and at the fan motor WHEN THE ENGINE IS RUNNING.
If you have +12 at the fan motor connection, check the ground wire going
to the fan motor. The fan motor gets its ground from the wire and not
from it's mounting.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277812 is a reply to message #277809] |
Wed, 13 May 2015 23:36 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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I'll have to get out a parts book and see if I can find a number. It should be a common part used in just about everything GM of that vintage. As a side note the resistor pack is NOT used in the highest speed. So you should have the highest speed without the resistor pack connected. I'll go look at the GMC schematic and verify what I just said is true.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277828 is a reply to message #277827] |
Thu, 14 May 2015 10:17 |
Daniel DeLuca
Messages: 120
Registered: June 2014
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Bill,
I was able to also track down the AC Delco part number, 336403. $15 at amazon.
This is going to get off topic now, but I have a parts book but always found the part numbers next to useless. Is there there any trick to cross referencing the part book number with modern numbers. This is the first time I have come across the GMCMHparts.com site, thank you for that.
Dan
> On May 14, 2015, at 11:05 AM, Billy Massey wrote:
>
> An attempt to repair the links.
> Using the parts book (www.bdub.net/manuals/parts/GMCMH-Parts.zip) which
> yielded 3942651 and www.gmcmhparts.com and Google leads to:
>
> ECH BR530
> t
> or/_/R-ECHBR530_0298670859>
>
> 53-69315
>
> DR758
> d
> uralast-dr758.html>
>
> bdub
>
>
> -----Original Message-----
> From: Gmclist On Behalf Of Daniel DeLuca
> Sent: Wednesday, May 13, 2015 4:40 PM
>
> ... snip ...
>
> I already have a spare relay. Does anyone have a part number or source for
> a relay pack?
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #277851 is a reply to message #277814] |
Thu, 14 May 2015 22:52 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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That relay failing would not surprise me. The relay and the connectors / terminals on the relay burning are common failure points for that type of fan motor circuit.
Ken B.
Daniel DeLuca wrote on Thu, 14 May 2015 05:01Ken,
Perfect, looks like ACDelco 336403 is what you need to search for if you have a late model.
My multimeter tells me that the relay that activates the high speed is defective, even though it still clicks. Luckily I have a new relay in the parts bin already.
Thanks!
Dan
Sent from my iPhone
> On May 14, 2015, at 1:03 AM, Ken Burton wrote:
>
> I found two part numbers:
>
> 3929054 First design
>
> 3942651 Second design
>
> You probably have the second design.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #278060 is a reply to message #277811] |
Tue, 19 May 2015 20:28 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""It looks to me like the fan relay is energized when either, the fan
switch is in high, or the "Htr & A/C control" switch is in A/C or Def.
Therefore, if you want to hear the relay click, you would need to set
the control to either vent or htr. Then, moving the fan switch between
position 3 and 4 should make the relay click. A question, what useful
purpose does the delay relay have?
Daniel
""
The purpose of the delay relay is to allow the mode doors to move into position before the fan goes to high speed. The doors may not be able to overcome the force exerted by the fan on high speed. That relay is generally not available but you do see them on ebay once in a while. They are only on late model coaches.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Resistor Pack for blower motor -- shorted? [message #278076 is a reply to message #278060] |
Wed, 20 May 2015 08:00 |
Kimberlea Weeks
Messages: 675
Registered: July 2010
Karma: 6
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Senior Member |
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Per GMCMI Parts Interchange:
Heater, Blower Resistor
GMC original part: 3942651
AutoZone or Advanced: DR758
Car Quest: 53-69315
NAPA: ECH BR530
*Thank you for being a member and supporting the GMC Motorhome lifestyle.*
*Kimberlea Weeks*
VP Administration and Convention Manager
612.501.4600 | f.866.519.0047 | www.gmcmi.com
*GMC Motorhomes International*
1402 So. Cage Blvd | Unit 273 | Pharr | TX 78577-6288
*Mark on your calendar today!*
*GMCMI 2015 Fall Convention* | Friday, September 25 to Thursday, October 1
Central States Fairgrounds | Rapid City, South Dakota
On Tue, May 19, 2015 at 8:28 PM, Bob de Kruyff wrote:
> ""It looks to me like the fan relay is energized when either, the fan
> switch is in high, or the "Htr & A/C control" switch is in A/C or Def.
> Therefore, if you want to hear the relay click, you would need to set
> the control to either vent or htr. Then, moving the fan switch between
> position 3 and 4 should make the relay click. A question, what useful
> purpose does the delay relay have?
> Daniel
> ""
>
> The purpose of the delay relay is to allow the mode doors to move into
> position before the fan goes to high speed. The doors may not be able to
> overcome the force exerted by the fan on high speed. That relay is
> generally not available but you do see them on ebay once in a while. They
> are only
> on late model coaches.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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