Home » Public Forums » GMCnet » Heater and Air Conditioner Control Connections (I Hate It When I Have To Clean Up After Someone Else)
| Heater and Air Conditioner Control Connections [message #173985] |
Tue, 19 June 2012 23:32  |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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When removing the Air Conditioning components from a GMC that is being parted out, I was careful to not destroy anything I removed, but somebody before me had been somewhat ruthless. The dehydrator was gone for one thing. And the fact that the control panel was in the garage with all the vacuum lines and wires cut isn't going to make re-installing the hardware in mine any easier.
To cut to the chase, I need to recreate the 12VDC connection from the control panel to the compressor, through all the interim components. I understand everything except the part from the first two-way connector after the control unti to the next "box" in the wiring diagram.
According to the 12VDC Engine wiring diagram, the circuit for the air conditioning compressor is as follows:
HEATER & A/C CONTROL ASM--16 DK GRN--<2)--16 DK GRN--[DZ]---16 DK GRN--<2>--16 DK GRN--<2>--A/C AMBIENT SW R.P.O--<2>--16 DK GRN--A/C COMPRESSOR CUT-OFF PRESSURE SW R.P.O--16 BLK--<2>--16 BLK--A/C COMPRESSOR - R.P.O--16 BLK--|
I can understand the legend when it says a <2) or a <2> is a two-way multiple connector, but I can't make any sense of the [DZ]. The legend says it is a junction "LETTERED TERM WIRE CAVITY @ WIRE END OF 28 WAY CONN. (PART OF INSTR PANEL HARN ASM)" and the legend function is "INSTR PANEL HARN TO ENGINE HARN & FWD LP WRG. HARN." The legend says the location is the ENGINE COMPARTMENT - DASH PANEL UPPER RH SIDE".
Can someone provide a picture or better description, please? I can find a vague reference to an "INSTRUMENT PANEL HARNESS" in a figure in the MM, but can't find anything in the MM that details the connections in that INSTRUMENT PANEL HARNESS. When I dig into the dash, am I going to find a connector in that harness labeled "DZ"?
And on the AC Control itself, it looks like there are three spade connectors corresponding to the 12VDC coming in to the center "bus" and two others, one apparently for the "fan bus" that powers the fan in all modes and one for the "compressor bus" that powers the compressor when the control calls for A/C and Defrost. I have three problems with the A/C and Fan spade connectors: 1) They look like they have never been connected to anything. 2) I don't know which is which and 3) there is a "tab" in them that prevents a female connector from being inserted on them. I can figure out which is which with a continuity checker, but where did the fan and compressor wires connect to the control unit originally? It looks like, if the #14 brown wire from the fuse block connected to the center spade, there would have been a spade connector with a short #14 brown wire going to the switch. The wires on the switch had been cut before I appeared on the scene, so I have no way of knowing how it was wired originally.
I want to put this back according to the MM in case a subsequent owner has to fiddle with it.
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| Re: Heater and Air Conditioner Control Connections [message #173987 is a reply to message #173985] |
Wed, 20 June 2012 00:38  |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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I took a photo of my wiring harness. The big green wire comes
from the heater controls and provides power to the AC clutch.
The green wire comes out under the hood to a connector with a
black and green wire. The green goes to the temp control switch
and then to the high pressure cut-off switch. Then changes
color to black and follows itself back into the wiring harness
from the 2 wire mentioned above.
That part of the wiring harness goes back into the engine
compartment, where the black wire emerges next to the
AC compressor and connects to the AC clutch.
http://www.gmcmhphotos.com/photos/aircon/p44562-ac-clutch-wiring-harness.html
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Heater and Air Conditioner Control Connections [message #174034 is a reply to message #173985] |
Wed, 20 June 2012 11:09 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Sir: If you are adding air to a coach that came without air, you are probably going to run into another issue. The 455 without air had different pullies and alternator brackets and possibly water pump. The non ac lower pully has only 2 belts and is smaller and very rare.
| ahamilto wrote on Wed, 20 June 2012 00:32 |
When removing the Air Conditioning components from a GMC that is being parted out, I was careful to not destroy anything I removed, but somebody before me had been somewhat ruthless. The dehydrator was gone for one thing. And the fact that the control panel was in the garage with all the vacuum lines and wires cut isn't going to make re-installing the hardware in mine any easier.
To cut to the chase, I need to recreate the 12VDC connection from the control panel to the compressor, through all the interim components. I understand everything except the part from the first two-way connector after the control unti to the next "box" in the wiring diagram.
According to the 12VDC Engine wiring diagram, the circuit for the air conditioning compressor is as follows:
HEATER & A/C CONTROL ASM--16 DK GRN--<2)--16 DK GRN--[DZ]---16 DK GRN--<2>--16 DK GRN--<2>--A/C AMBIENT SW R.P.O--<2>--16 DK GRN--A/C COMPRESSOR CUT-OFF PRESSURE SW R.P.O--16 BLK--<2>--16 BLK--A/C COMPRESSOR - R.P.O--16 BLK--|
I can understand the legend when it says a <2) or a <2> is a two-way multiple connector, but I can't make any sense of the [DZ]. The legend says it is a junction "LETTERED TERM WIRE CAVITY @ WIRE END OF 28 WAY CONN. (PART OF INSTR PANEL HARN ASM)" and the legend function is "INSTR PANEL HARN TO ENGINE HARN & FWD LP WRG. HARN." The legend says the location is the ENGINE COMPARTMENT - DASH PANEL UPPER RH SIDE".
Can someone provide a picture or better description, please? I can find a vague reference to an "INSTRUMENT PANEL HARNESS" in a figure in the MM, but can't find anything in the MM that details the connections in that INSTRUMENT PANEL HARNESS. When I dig into the dash, am I going to find a connector in that harness labeled "DZ"?
And on the AC Control itself, it looks like there are three spade connectors corresponding to the 12VDC coming in to the center "bus" and two others, one apparently for the "fan bus" that powers the fan in all modes and one for the "compressor bus" that powers the compressor when the control calls for A/C and Defrost. I have three problems with the A/C and Fan spade connectors: 1) They look like they have never been connected to anything. 2) I don't know which is which and 3) there is a "tab" in them that prevents a female connector from being inserted on them. I can figure out which is which with a continuity checker, but where did the fan and compressor wires connect to the control unit originally? It looks like, if the #14 brown wire from the fuse block connected to the center spade, there would have been a spade connector with a short #14 brown wire going to the switch. The wires on the switch had been cut before I appeared on the scene, so I have no way of knowing how it was wired originally.
I want to put this back according to the MM in case a subsequent owner has to fiddle with it.
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C. Boyd
76 Crestmont
East Tennessee
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| Re: Heater and Air Conditioner Control Connections [message #174046 is a reply to message #174039] |
Wed, 20 June 2012 11:31 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Yes Sir, the crankshaft pully has to have 3 groves and is larger dia than the 2 pully. Some non ac 455s had the correct waterpump if it had Towing package. There is a difference in the snout legnth. Of course it being a motorhome I would expect it to have the big waterpump, but no guarantees..
[/quote]I got part of that covered in that I got the alternator bracket while I was getting the A/C compressor. Gonna change the water pump anyway. What lower pulley are you talking about? The one on the crankshaft?[/quote]
C. Boyd
76 Crestmont
East Tennessee
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| Re: Heater and Air Conditioner Control Connections [message #174048 is a reply to message #174047] |
Wed, 20 June 2012 11:34 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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What year ac are you adding to the 73 ??? There are 3 types.
| ahamilto wrote on Wed, 20 June 2012 12:32 |
I think that clears up the [DZ] part of the wiring harness question. Now all I need is a picture of a control unit with the fan and A/C compressor wires still attached so I can recreate that.
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C. Boyd
76 Crestmont
East Tennessee
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| Re: Heater and Air Conditioner Control Connections [message #174071 is a reply to message #174056] |
Wed, 20 June 2012 14:46 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Senior Member |
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Let me ask a dumb question here: Why not just put an ad-on type a/c instead of installing one that didn't work well when it was new? If I had the brains, the ability, and/or the money, that's what I'd do. In fact I might put two in...one under the dash and one in a compartment somewhere so the whole coach would be cool.
I suppose if this is a period restoration it would matter, but other than that reason or pure aesthetics, I can't imagine why.
To paraphrase Ken Henderson, maybe it is because "you can." Just curious.
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: Heater and Air Conditioner Control Connections [message #174082 is a reply to message #174071] |
Wed, 20 June 2012 16:26 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| Stick Miller wrote on Wed, 20 June 2012 14:46 |
Let me ask a dumb question here: Why not just put an ad-on type a/c instead of installing one that didn't work well when it was new? If I had the brains, the ability, and/or the money, that's what I'd do. In fact I might put two in...one under the dash and one in a compartment somewhere so the whole coach would be cool.
I suppose if this is a period restoration it would matter, but other than that reason or pure aesthetics, I can't imagine why.
To paraphrase Ken Henderson, maybe it is because "you can." Just curious.
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It isn't that much work to replace the blower box. Everything else has to be done anyway (mount compressor, mount condenser, purge, vacuum, charge, yada yada yada). And I am going to do the mods to increase the airflow in it. FWIW, I do plan to add a secondary evaporator overhead behind the driver's seat for the passengers. Between the dash and that one, I should be able to go down the road without having to run the roof unit. If I can't get comfortable, I may replace the dash part with a better one. Bottome line is that I am NOT going to run the generator while traveling just to run the roof air. That seems insane to me.
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| Re: [GMCnet] Heater and Air Conditioner Control Connections [message #174109 is a reply to message #174071] |
Wed, 20 June 2012 18:58 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Doesn't strike me as 'dumb', it's a good idea. Most of the needed components for a dual system could be had from an older Suburban with rear A/C. Fit the highest capacity A6 compressor and use the Suburban 'Y' pipe to feed the two evaps. You'd have to fab plumbing but any good auto A/C shop ought to be able to set you up. My HVAC design cousin says there's no magic in that system... when you turn the rear A/C on, the airflow turns the expansion valve on (assuming it's above the set point) and the compressor simply cycles ON for a longer period before the line pressure switch cycles it off.
I wonder - and perhaps the trucker(s) on the list know - how these things they run at night, 'Rigmaster' is one trade name, which keep the A/C going with the engine off. If you had a second evaporator as above, maybe you could fit a pony engine in the generator bay and spin a compressor with it and cool the coach with the two 'engine' systems. You could get a couple hundred pounds and some drag off the roof.
--johnny
'76 23' transmode norris
'76 palm beach
From: Stick Miller <stickmiller@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, June 20, 2012 3:46 PM
Subject: Re: [GMCnet] Heater and Air Conditioner Control Connections
Let me ask a dumb question here: Why not just put an ad-on type a/c instead of installing one that didn't work well when it was new? If I had the brains, the ability, and/or the money, that's what I'd do. In fact I might put two in...one under the dash and one in a compartment somewhere so the whole coach would be cool.
I suppose if this is a period restoration it would matter, but other than that reason or pure aesthetics, I can't imagine why.
To paraphrase Ken Henderson, maybe it is because "you can." Just curious.
--
Stick Miller
'78 Royale - she left me for another man
Americus, Georgia
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Heater and Air Conditioner Control Connections [message #174369 is a reply to message #174348] |
Sat, 23 June 2012 11:50 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Sir: I can`t find an interchainge on the pulleys. It would be worth checking tho as it probably is the same. The 350 diesel is "the" block you want to build, or at least me if you want to get rid of it. The main journals on all small blocks is 2.5" except the diesel which is 3.0" same as the big blocks, so you can use a 425 big block crank and get 411 cu in. If you shave the crank and bore to 4.25 you get a 451 cu in small block and be able to run a nice intake without floor issues.
If you can`t find a crank pully let me know, $10 +.
| ahamilto wrote on Fri, 22 June 2012 21:31 |
| C Boyd wrote on Wed, 20 June 2012 11:09 |
Sir: If you are adding air to a coach that came without air, you are probably going to run into another issue. The 455 without air had different pullies and alternator brackets and possibly water pump. The non ac lower pully has only 2 belts and is smaller and very rare.
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As I said before, I did get the alternator bracket.
I have a 1981 Cutlass 350 diesel that developed a crank knock back in 1992 so it has been parked in the pasture ever since.
Are the crankshaft and waterpump pulleys from that 350 diesel the same as the ones on the Olds 455s with AC?
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C. Boyd
76 Crestmont
East Tennessee
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