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#1
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Heater Control Valve 4.8is Cabin Temperature
The issue is this: when the truck is turned on and creeps toward operating temperature (and at operating temperature), the front & rear cabin temperature is nice and warm and cozy. But, after about 15 to 20 minutes of driving the front cabin temperature drops off to what feels slightly cooler than room temperature while the rear climate control vents (back side of center console/arm rest) is still billowing out pretty toasty air. The dash center vent dial is also set at warm. However, setting this dial to cold makes the air unpleasantly cold. Real cold. To the touch, the hoses at the heater control valve are warm/hot between the rad and valve, but from the firewall to heater control valve those two respective hoses are warm, but not scalding. Turning the key to POS 2 and touching both solenoids on the heater control valve appear to be working but I'm not exactly sure how obvious this is supposed to be. Conducting a continuity test shows that the installed unit is showing continuity between pins 1+ & 3- as well as 1+ & 2- (three pin connector). This test is consistent with a new heater control valve unit I have. The current heater control valve can possibly be fried, yet looking new. That wouldn't be uncommon. However, the heat throughout the car for the first 15 minutes or so then falling off once I get on the freeway is consistent and perplexing to me. Are there any other tests I can perform before replacing this heater control valve or worse - getting into the dash for something else?
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2006 E53 4.8is - Imola Red 2, Cream Beige all day er’ day |
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#2
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You have the recirc mode on? Got to eliminate the easy stuff first.
Electrically is not the heater control valves usual mode of failure. Typically the inside valves get gummed up as the rubber deteriorates over time. Have not seen an electrical failure yet over my, admittedly small, sample size of 5ish. If you are so inclined to open up the old one it is rather easy and would allow inspection. Only "gotcha" is to be careful of the small wire leads. But you are getting heat in the rear so I'm not sure the valve is your issue. Maybe a diverter flap (the fresh air one for instance) is stuck and not closing?
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2005 X5 4.4i Build 04/05 Maintenance/Build Log Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles) 2006 X5 4.8is Build 11/05 Maintenance/Build Log Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles) 2010 X5 35d Build 02/10 Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles) |
#3
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Heater valves are are open at rest state and closed with PWM voltage from IHKA (AC control unit). When the problem occurs you can disconnect the plug on valves for test purposes.
If the fan inside IHKA fails the temperature inside the unit (where interior heat sensor is also located) warms up after longer drive and can cause lower heat demand than anticipated. You can use smoke or a piece of paper to test if air is drawn into IHKA via the grill on the fascia. |
#4
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Be sure you have enough coolant and heat cycle and bleed the air and check the fluid level a couple times. On my 3.0 I have a slow coolant loss some where yet to be determined and when it gets a bit low but not overheating, the forward heater blows cold.
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#5
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I am chasing something similar..In my case the passenger side gets cold with no warning after 15 minutes or so of driving.
My Heater control valve also looks new and shiny..Previous owner said he replaced it. Since it has the elec connector on the side closest to brake booster, I know it is not OEM (OEM has it on the engine side). And the OEM unit was not shiny. I haven't replaced it yet, but I hear bad things about aftermarket heater valves. |
#6
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Quote:
Oh my god, recirculation mode was on. Just kidding, it's off. The diverter flap, where is this located? What is this IHKA and where is it located? Quote:
Plenty of coolant, new cap and properly bled with the temp setting on high, blower low and all that good stuff. Quote:
Keep me posted in what you find!
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2006 E53 4.8is - Imola Red 2, Cream Beige all day er’ day |
#7
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IHKA = AC control panel.
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#8
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Wife’s car will act pretty similar and seems to be related to the sampling fan in the dash.
Example: my car will stay nice and cold when set to 73°, or nice and warm when set to 73°. Hers on AC tend to have to use 69-70 or 75-76 to get the same cabin heat. I’ve cleaned the grill on the sampling fan and it improves, but never as good as my car. A good test for the sampling fan is with the controls on auto , set the temp lower until the fan speed drops to almost nothing that will tell you what the dash thinks the temp of the cabin is. If that doesn’t match it’s almost certainly the sampling fan
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#9
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What fault codes do you have (Carly other other software that read the body and other modules)? IHKA part could be it. Given the age of the car, whilst not the typical symptoms, it could be a good time to proactively replace the final stage resistor (FSR).
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2002 Euro X5 (E53) 3.0 diesel (M57) 5 speed manual with UUC short shifter. Pre-xDrive NV125 transfer case (chain & gears). Factory Xenon headlights, Spyder LED tail lights Updated vortex crankcase breather. Motorsport dead pedal, factory fire extinguisher, factory first aid kit, factory F&R mud flaps, factory PDC Bilstein B6 shocks F&R Redline oil has replaced "lifetime" fluids (F&R diff, manual transmission, transfer case and P/S). Dimple magnetic drain plugs in all compartments. |
#10
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What was the ambient temp outside when having the issue? A very common cause is a stuck open thermostat.
The dial on the dash looks like but is not a gauge. It’s more of a 3 position idiot light. Pull up the actual engine temp with the hidden menu (I think it’s 9 ) and confirm the temp gets to and stays close to 90 c. (Might be slightly different on the 8, I have the 6).
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
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