Page 7 (Updated 25-Oct-2008)
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Cabin Climate Control
- A/C Air Condition [manual]
- Tune Up -insulation
- Cabinet Heating System
- Once in a lifetime Cleanup
- Troubleshooting
Free Service Manual, Free Download.....see FAVORITE LINKS -page 26- FAVORITE LINKS
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Air Condition System
A/C fluid system and piping overview.
1. Belt driven Compressor free clutch ; 2. Pressure relief valve (pressure side) ; 3. Dual pressure switch, sight glass ; 4a. Pressure switch, electrical connection to ECU ; 5. In-Line filter ; 6. Expansion tube (expansion orifice) ; 7. Condensed water outlet through the firewall (see pic below); 8. Cold (excess leftover) low pressure return line(to be insulated) Note: blue arrows = liquid flow direction
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A/C Electronics Control :
a. - A/C switch and Cabinet Fan sw has to be activated, connected to ECU. Cabinet 4-speed fan is supplied via speed resistor (dashed line).
b. - Thermo Control Amp, cooled air temp sensor; enable to ECU.
c. - System pressure switch at Liquid Tank; ok -input to ECU
d. - Relay box; three relays (yel)& AC/engine cooling fans have to be ok. Relays 1&2 are for fans 1&2, Relay3 for their high speed. Fourth relay (red) for compressor clutch.
e. - A/C &engine Cooling Fans (2pcs)
f. - After the prerequisites a -to- d have been met, ECU will use a relay (red) to deliver +12V to compressor clutch. Energized clutch connects, and belt driven pump starts pressurizing, circulating cooling liquid.
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Note: fast kickdown (TPS given -info) will cause ECU to disengage A/C clutch during acceleration.
Note2: refer to wirings diagram for actual connections; a to c components are connected in series to ECU pin 46.
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Compressor supply wire, ..... Liquid tank under hood, front right (located under water reservoir)
Liquid tank (also called receiver dryer) contains desiccant to counter system degrading acids and water accumulating into the coolant. Desiccant is a chemical that attracts moisture. When system is functional, coolant bubbling is seen through the sight glass.
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Air Condition Schematics. At right view from below: condensed water outlet in the firewall.
Cooled Air condenses in the evaporator while it is being cooled. This water is being led out through the firewall (7.) to engine bay via the rubber nozzle: manuals are silent on this issue.
Note: Using A/C during winter keeps cabin dry: windows stay clean from moist & frost.
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(For detailed A/C info google "accumulator orifice tube system" or check: http://www.id-usa.com/how_to_ac.asp
http://www.id-usa.com/how_to_videos.asp)
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Tune-Up Insulation
Do you feel cold in HOT maxima? Is your car not cool enough?
GlobAll warmup to cabin: insulate heater & A/C tubing.
Happily there is simple solution: Wisely created men have created -bang- us THE insulation. So if you want more heat into u cabin in winter, insulate your heating tubes under the hood. And if you want more cold into u cabin in summer, insulate your A/C tubes under the hood. After DIY insulation, summerday A/C input air temp at dash inlets drops from +15C down to---> +8C and to anybody who has been around temp problems, knows that’s a lot atshii! ...over 60% more kick. (12 degrees F colder)
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A/C into compressor -hose Insulation
In the summertime under idling, STANDING car hood, temps rise very high. In Maxima there is four? feet of cold piping (see pic above, 8.) coming from the cabin to be compressed again, under these water boiling conditions. The A/C system is trying -feverishly- to make winter...
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Cabin heater input hose insulation.
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Cabin Heater Coolant flow (see also next page) 7.Heated Coolant flow, 14.Heater input hose valve, 17. Cabin Heater Core.
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The Heater input hose valve seems to be on/off valve used only to close coolant flow when full cold switch is activated. All incoming air temp adjustment is done via the airmix door (below, item 2.). See next page for valve details. FSM page HA-120 explains this valve and calls it 'Water Cock Solenoid Valve'. (check/download FSM via 'Favorite Links', at top left. Theres also very thorough troubleshootin guide.)
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In winter, your cabin heating pipes (see pic above, 7.) stand bare in subzero wind under the hood. If u calculate this tube area and heat energy escaping via it to atmosphere, while DRIVING, u find out that quite a lot energy has vanished into the wind (possibly 1.5kW) from the cooling liquid before it hits your heater core.
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Cabinet Heating System
Heater Unit - Cooling Unit - Intake Unit ...under the dashboard:
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Cabin air heater/cooler illustration. Temp Control lever at max HOT position, Fresh Air mid dash vent (F) open.
The cold air goes via fresh vent only to middle cabin outlets. The green arrow shows the fresh air flap (US models) and its panel operation switch. Heater lever controls electronically heater water valve (see next page) AND operates the Air Mix Door (2.) in the illustration (dashed line). Full Cold flap (1.).
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Dasboard climate control assy, Xplode views:
- Numbers at left: Two micro size lamps (1.) provide light via illuminator plate to knobs (3.). Leds are used in the end of control levers 2a. & 2b. There are two bulbs on the left side also For Fresh Vent (not seen here).
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The Fan Switch and Temp Control levers might become stuck in the plastic assy grooves they travel: squirt some lithium grease inside the base rail guide from outside (no need to open).
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This 'view' is inverted = from below, schematics (refer to p.5 fuse panel):
Temp Control lever seen at max HOT position.
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Full Cold operation:
Temp Control lever seen at max COLD position.
1. Full cold flap seen opened with full cold motor
2. Air mix door at full cold position
- At right: airflow with these settings
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Max COLD position functional schematics.
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Cabinet Flow Control Valve ---> see next Page 8
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Panels & Climate control Removal:
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1. Insert small screwdriver between panels, pull [red] shifter panel up
2. Likewise pull up switches [blu] & disconnect from the grn panel
3. Take ashtray out [if necessary radio]
4. Take out grn panel four screws [grn arrows]
5. Pull [grn] panel out, disconnect cig & hazard connectors
6. RH pic: Disconnect all wirings behind climate assy
7. Take four screws out and pull assy out. Here I forcefully bent [grn arrow] the dash RH lower support to easily slide the assy out
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Once in a lifetime Cleanup
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View behind glovebox: blower motor & its speed resistor (redlined), inset: artistic view into inside dirt filled cooler cell via the resistor hole (evaporator).
Take out the glovebox. Next take the blower resistor connector and outer 2 screws off, pry open. Take a vacuum cleaner and clean the 'squirrel nest' to get unobstructed airflow. Its also easy to take the blower motor 3 screws, supply connector and airhose out and clean the fan blades with soap and water. Also wipe clean all air intake walls. (I have duct-taped a ½-inch small extension hose into vacuum cleaner to reach and suck all that accumulated dirt away.) You need a good light to zoom into the farthest corner and long stick to scrape all dead mass into the sucker.
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Troubleshooting
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First time had to do smtg on my new diesel [read: freezer golf] Golf. That vehicle had a genius de signer: four foot hose starts from front, is almost visible outside...
This is 'first thing' I do with any car I touch, thereby did not measure this 50th ? rig. But think of the basic physics: this tube [good heat radiator] area must be near your heater core capacity. All this sits in the freezing wind as u drive. Cannot say the numbers inside cabin, but the change is enormous.
As insulation u can use almost anything with insulation capacity ['porous' characteristics] which is easy to strap on. I used the free plush -garment strips I have used for soundproofing [super stuff!]; they have a thin foam layer. Winded it on, and used tie-wraps to secure [this is important! not to burn u vehicle with smtg dropping on the exhaust pipe]. There are always people who tell this and that of flammability: but think what is rubber? ...next: what is rubber hose with gas inside??? ...my car is full of such potential 'gas-rubber-bombs'. So almost anything goes, in insulation first 1/4 inch is important.
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Heater does not work? --->see next page 8.
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A/C does not work?
Basic functions check:
Compressor does not come on? You can hear the compressor free-clutch to engage if u open the hood, as smbdy puts AC on. If it does not, ctrl is amiss. (bad ctrl board or ECU?) Feel for the cooling hose, is system pumping cold?
The compressor itself has one wire going in: as all ctrl requirements are met, AC relay connects +12V to the compressor single supply connector.
- Check that fluid level switch is closed(Dual pressure switch). If not, switch bad, fluid level low. (also a suspicious note in the schema: FUSIBLE CONNECTOR ...check out!)
- See for the sight glass see pic above no(3.), clean: bubbling if liquid flows.
- Check that thermo (with a sensor) control amp closes. It is located at cabinet cooling unit (evaporator), left from blower motor resistor. Via this and dual press sw +12V is supplied to ECU-pin46.
You may shortly test compressor and its clutch by opening the connector and jumping +12V from battery to that connector, compressor should engage. Do this only shortly for testing: Bypassing pressure switch will cause too high pressure resulting in leak. Too low pressure and bypass -forced compressor ON, will ruin the compressor.
ECU will not enable A/C if fans/fan relays do not work: three relays for fans, one for AC. Any of them may be stuck. Replace if suspect; test by hitting with handle of a small screwdriver.
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Compressor Relay Engagement Preconditions:
Relay closes when ECU-pin9 (A/C-enable) goes down after following conditions are met:
1. Dual pressure sw at the liquid tank closed.
2. Thermo Control Amp closed.
3. Fuses ok and +12V to relays, Climate Ctrl fan switch ok
4. Cabinet Fan switch at 1-4, A/C pushbutton switch close & supply +12V to the relay coil.
5. Two Fans at radiator & their ctrl Relays, voltage supply ok.
6. TPS input to ECU (see below & page 6)
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The Fan control and A/C enable is driven by ECU. Check that the A/C relay coil gets fused +12V and is grounded via ECU-pin9 low. Note that while driving, hitting gas pedal to bottom (TPS signal), ECU is programmed to disengage A/C compressor during acceleration.
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Common A/C problems:
Poor cooling, Rapid compressor cycling, Evaporator outlet warm
- Low refigerant, Leaks, Faulty compressor, clogged In-Line filter and/or orifice
---> Repair leaks, normal service
Continuous compressor operation, Evaporator iced, poor cooling & airflow. (In the beginning system works fine before icing)
- Thermostatic control amp faulty, Compressor relay stuck, System overcharged with refigerant
---> Replace faulty components, fillup procedure
Poor cooling at low speed, Engine overheats
- Restricted airflow through condenser
---> Clean debris from condenser, straighten bent condenser fins
The relay box under water reservoir; the three fan relays
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"While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease." Genesis.
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