Home » Public Forums » GMCnet » heater wiring (fire damage wiring repair(final stages))
| heater wiring [message #162550] |
Fri, 09 March 2012 11:11  |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I have a 77 Royale with a 455 and 6kw onan. The onan has its own battery with a 2 gauge + running from the Generator up to the engine compartment. There is a house battery and coach battery in the right front of the engine bay. In the fire much of the wiring on the firewall burned away but most of it has been identified and replaced but there are a couple of small remaining mysteries. On the heater box which houses the evaporator and heater core there is a device which has four wire taps or blades for connecting wires to it and some coils or resister type things protruding off the other side. This part mounts in a hole in the drivers side of the heater box and protrudes into the box. What is this thing and where do the wires from it go??
On the passenger side of the heater box but mounted high on the raised firewall electrical panel is another device which looks similar to the horn relay. It is badly melted and has nubs of wires coming from it. Anyone have an idea of its function and how it is to be wired?
Hopefully my description is not too vague. Any links to photos or instructions would be greatly appreciated.
Thanks,
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: heater wiring [message #162552 is a reply to message #162550] |
Fri, 09 March 2012 11:23  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Sully,
The first may be the fan resistor --
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4157
Dennis
| sgltrac wrote on Fri, 09 March 2012 11:11 |
I have a 77 Royale with a 455 and 6kw onan. The onan has its own battery with a 2 gauge + running from the Generator up to the engine compartment. There is a house battery and coach battery in the right front of the engine bay. In the fire much of the wiring on the firewall burned away but most of it has been identified and replaced but there are a couple of small remaining mysteries. On the heater box which houses the evaporator and heater core there is a device which has four wire taps or blades for connecting wires to it and some coils or resister type things protruding off the other side. This part mounts in a hole in the drivers side of the heater box and protrudes into the box. What is this thing and where do the wires from it go??
On the passenger side of the heater box but mounted high on the raised firewall electrical panel is another device which looks similar to the horn relay. It is badly melted and has nubs of wires coming from it. Anyone have an idea of its function and how it is to be wired?
Hopefully my description is not too vague. Any links to photos or instructions would be greatly appreciated.
Thanks,
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: heater wiring [message #162553 is a reply to message #162552] |
Fri, 09 March 2012 11:27 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Here is another photo showing the wiring to the connector/resistor.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=24564&title=img00558&cat=4929
Dennis
| Dennis S wrote on Fri, 09 March 2012 11:23 |
Sully,
The first may be the fan resistor --
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4157
Dennis
| sgltrac wrote on Fri, 09 March 2012 11:11 |
I have a 77 Royale with a 455 and 6kw onan. The onan has its own battery with a 2 gauge + running from the Generator up to the engine compartment. There is a house battery and coach battery in the right front of the engine bay. In the fire much of the wiring on the firewall burned away but most of it has been identified and replaced but there are a couple of small remaining mysteries. On the heater box which houses the evaporator and heater core there is a device which has four wire taps or blades for connecting wires to it and some coils or resister type things protruding off the other side. This part mounts in a hole in the drivers side of the heater box and protrudes into the box. What is this thing and where do the wires from it go??
On the passenger side of the heater box but mounted high on the raised firewall electrical panel is another device which looks similar to the horn relay. It is badly melted and has nubs of wires coming from it. Anyone have an idea of its function and how it is to be wired?
Hopefully my description is not too vague. Any links to photos or instructions would be greatly appreciated.
Thanks,
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] heater wiring [message #162555 is a reply to message #162550] |
Fri, 09 March 2012 11:28 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Sully, the device installed in the heater plenum on the drivers side of the
heater box is the resistor set that controls the heater motor speed. Any GM
car from this era could be a donor for this part if you can't find one new.
The relay looking thing located high up on the passenger side of the heater
is the delay relay for the high speed blower operation. It works in tandem
with the other relay located a little bit lower on the plate. It could
prove hard to find, but not impossible. Try NAPA stores first, they seem to
have a good supply of GMC lighting and 12V electrical parts. The wires go
from the fuse block to the heater controls in the dash and then to the
relays and resistor and eventually to the heater motor, and from there to
ground. Clear as mud, right. I still am planning to come to Seattle in the
next few days. Hope to see you then.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Mar 9, 2012 at 9:11 AM, sgltrac <sgltrac@gmail.com> wrote:
>
>
> I have a 77 Royale with a 455 and 6kw onan. The onan has its own battery
> with a 2 gauge + running from the Generator up to the engine compartment.
> There is a house battery and coach battery in the right front of the engine
> bay. In the fire much of the wiring on the firewall burned away but most of
> it has been identified and replaced but there are a couple of small
> remaining mysteries. On the heater box which houses the evaporator and
> heater core there is a device which has four wire taps or blades for
> connecting wires to it and some coils or resister type things protruding
> off the other side. This part mounts in a hole in the drivers side of the
> heater box and protrudes into the box. What is this thing and where do the
> wires from it go??
> On the passenger side of the heater box but mounted high on the raised
> firewall electrical panel is another device which looks similar to the horn
> relay. It is badly melted and has nubs of wires coming from it. Anyone have
> an idea of its function and how it is to be wired?
> Hopefully my description is not too vague. Any links to photos or
> instructions would be greatly appreciated.
>
> Thanks,
>
>
> --
> Sully
> 77 Royale basket case.
> Future motorhome land speed record holder(bucket list)
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: heater wiring [message #162580 is a reply to message #162550] |
Sat, 10 March 2012 02:04 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Sully:
As everyone is saying, that coil is the the resistor network for the blower motor. Those coils get very very very HOT. Red hot in fact. That is why they are in the HVAC Plenum where there is air moving to keep them cool, and to keep the heat where there is less likely to have flammable material around But mostly to keep the coils from burning out. They will if not in that air stream.
The wiring harness from that plug goes around the front of the HVAC box around to the firewall plug, the relay, and the blower motor on the passenger side. I have a picture of that area of the relays in that area. However mine is a 1974. But you will get the idea.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=43137&title=heater-fan-relays&cat=6030
Each individual wire is not clearly shown in this picture because of the bundling and cleanup I've done. Sorry. However the wiring diagrams will give you a clear picture. I've downloaded them from one of the sites and use them a lot. You should download it as well.
http://www.bdub.net/factory-manuals.html
In the 77 wire diagram, There are two relays for the blower motor. One is a delay relay and the other connects the blower directly to the battery and alternator output on high speed. (Gets as much voltage to the fan as possible) There is also a wire that goes to the fan motor that look like this.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=43104&title=pn-8913700&cat=6030
I have a post about this noise capacitor because of the problems related in the same photo folder
I noticed that your temperature blend door cable has a broken ear and therefore will not change temperature of your heater. I had the same problem and I posted a repair that I used. You can buy a new cable but This worked real well. Check out the entire album of pictures for the process.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=43116&title=heater-blend-door-cont&cat=6031
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] heater wiring [message #162590 is a reply to message #162555] |
Sat, 10 March 2012 10:24 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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The delay relay was used on some 1977 and all 1978 GMCs with air conditioners.
These had a MAX setting on the air conditioner switch.
The delay relay was used to make sure that the flapper in the air duct of the heater/air conditioner (controlled by vacuum) could move into position before the fan started blowing. It was felt by GM that the high air flow when on the MAX position could prevent the flap from moving properly.
To the best of my knowledge that delay relay is not available anywhere. I spent a long time a few years back trying to find a source but since it was used on so few vehicles (probably just the GMC motorhome) no one is making it or a substitute any longer. Unless someone started to very recently but I don't think so.
Probably the only way to get one is to salvage a used one from a 77 or 78 GMC Motorhome that someone is parting out.
Here is something that I had posted back in 2005.
>
> For those of you that might be looking for the time delay relay for the blower motor on the GMC here is more information.
>
> The GM part number is 366408.
> I have been examining the original part and find that it is marked as follows:
>
> CHEVROLET
> PN00366408
>
> On the terminal side of the relay it shows:
>
> Natron Corp.
> Reed City, MI 49677
>
> In checking the Internet I see that this company is still in existence. Their web site is:
> http://www.natron.com
>
> They show and address of 5000 North US-131
> Reed City, MI 49677
> 231-832-5525
>
> Anyone near there want to follow up on this?
> I am driving in the morning to Phoenix with my GMC to visit my son and his family for Thanksgiving.
> If no one has checked with them by the time I return in about a week, I will do so.
>
> I have also found a Universal Accessory Time Delay relay in the NAPA parts book that could probably be used to replace the oringinal.
> It also have 4 terminals. A ground, a power to the coil and the two wires that would go in series with the motor wire. One would have to cut the existing wires from the 4 prong terminal connector and use individual spade connectors.
>
> This is NAPA part number AR688.
>
> I can check the wiring diagram when I get back and determine which color wires go to the terminals 85,86,87 and 30 on the Napa relay. Right now, looking at the terminal diagram in the NAPA book, I can guess that the motor wire would go to 30 and the ground to 85 and the yellow wires to 86 and 87.
>
> Also, note that the original part says CHEVROLET. Perhaps we can find a Chevrolet application from that time period and get a cross on a relay that might just plug right in.
>
> Meanwhile, if anyone tries the NAPA part and it works, let me know.
I contacted the company in Reed City at that time and they told me that they no longer produced it.
Many people including myself have just eliminated the relay and connected the wire from the blower relay directly to the fan motor.
Here is another posting that I first made several years back which might help with someone trying to wire up their blower.
--------------------------
The 77 and 78 models had a time delay relay mounted above the blower relay. Your 78 will have this. There are three relays. The top one is the time delay relay. The middle one is the blower relay and the lower one is the horn relay.
I will repeat something that I have posted in the past:
The delay relay is the smaller relay at the very top of the panel. It has two leads - on mine they are brown and yellow and one has a male and the other a female terminal at the end of the leads. The leads are approx. 6 to 8 inches long. The female one connects to the male terminal on the lead to the blower motor. The male one leads to the short lead (purple on mine) that goes to the blower relay (terminal 1). If the delay relay burns out you can plug the male motor lead directly into the short female lead going to terminal 1 on the blower relay.
The blower relay (below the delay relay but above the horn relay) has 5 terminals. When the blower relay is mounted with the 5 terminals down, there are two on the left, one in the middle and two on the right.
On the back left side it is #3 which has a red/white wire that leads to a fusible link and that goes into the harness and connects to the red wire from the alternator to the center stud of the battery isolater.
On the front left is terminal #2. Mine has a dark blue wire that leads to the resistor package in the right side of the heater box.
In the center is terminal #1. Mine has a short purple wire with a female connector. The male lead from the delay relay plugs into this (on mine right now I have the blower motor plugged into this as my delay relay is bad and disconnected).
On the right rear is terminal #5. This has a short black lead that goes to a ground screw.
On the right front is terminal #4. This has an orange wire that leads to the heater controls on the dash.
Terminals 4 & 5 control the coil in the blower relay.
Terminals 1 & 2 are normally closed and operate the blower when in low or medium speeds.
Terminal 1 & 3 are normally open but when the dash switch is put in "high" or "max" it actuates the coil and the relay connects these terminals which give power to the blower directly from the alternator in order to get higher voltage and higher blower speed. At the same time it disconnects terminal 2 from the circuit.
-----------------------------------------
Emery Stora
On Mar 9, 2012, at 10:28 AM, James Hupy wrote:
> Sully, the device installed in the heater plenum on the drivers side of the
> heater box is the resistor set that controls the heater motor speed. Any GM
> car from this era could be a donor for this part if you can't find one new.
> The relay looking thing located high up on the passenger side of the heater
> is the delay relay for the high speed blower operation. It works in tandem
> with the other relay located a little bit lower on the plate. It could
> prove hard to find, but not impossible. Try NAPA stores first, they seem to
> have a good supply of GMC lighting and 12V electrical parts. The wires go
> from the fuse block to the heater controls in the dash and then to the
> relays and resistor and eventually to the heater motor, and from there to
> ground. Clear as mud, right. I still am planning to come to Seattle in the
> next few days. Hope to see you then.
> Jim Hupy
> Salem, OR
> 78 GMC Royale 403
>
> On Fri, Mar 9, 2012 at 9:11 AM, sgltrac <sgltrac@gmail.com> wrote:
>
>>
>>
>> I have a 77 Royale with a 455 and 6kw onan. The onan has its own battery
>> with a 2 gauge + running from the Generator up to the engine compartment.
>> There is a house battery and coach battery in the right front of the engine
>> bay. In the fire much of the wiring on the firewall burned away but most of
>> it has been identified and replaced but there are a couple of small
>> remaining mysteries. On the heater box which houses the evaporator and
>> heater core there is a device which has four wire taps or blades for
>> connecting wires to it and some coils or resister type things protruding
>> off the other side. This part mounts in a hole in the drivers side of the
>> heater box and protrudes into the box. What is this thing and where do the
>> wires from it go??
>> On the passenger side of the heater box but mounted high on the raised
>> firewall electrical panel is another device which looks similar to the horn
>> relay. It is badly melted and has nubs of wires coming from it. Anyone have
>> an idea of its function and how it is to be wired?
>> Hopefully my description is not too vague. Any links to photos or
>> instructions would be greatly appreciated.
>>
>> Thanks,
>>
>>
>> --
>> Sully
>> 77 Royale basket case.
>> Future motorhome land speed record holder(bucket list)
>> _______________________________________________
>> 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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| Re: [GMCnet] heater wiring [message #162593 is a reply to message #162590] |
Sat, 10 March 2012 11:08 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""The GM part number is 366408.
""
You're right in that they are no longer made, but I've had luck finding NOS available on Ebay now and then. If someone is not in a hurry, you will see them pop up, but frankly, you can do just fine without the relay. I usually turn down the fan speed when changing HVAC modes and when the doors have moved, you can turn the fan speed back up--it's a very minor inconvenience.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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