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#1
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help! haunted heat
My climate control on my 84 300sd is haunted.
Only first thing in the morning the defroster will work but if i put it on any other setting the fan stops and cold air comes out the center vents. After a while pushing buttons it will work normal for the rest of the day then the next morning same thing occurs. changed the engine temp interlock I have grounded the engine temp interlock. tried different temperature regulators. fan speed controllers 2 different ones ccu 5 different ones soldered ccu changed interior temp sensor 3 times unplugged electric water pump And yet the same thing occurs occasionally it works right. I can't figure it out any ideas? Steve
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85 300d in progress |
#2
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Normal?
I'm not familiar with the 126 but what you're describing sounds like normal operation to me. On my 123 the blower won't operate on anything but defrost until the engine warms up to a certain temp. (Can't recall the exact temp tho)
I would assume the 126 system is set up the same way. FWIW- My Chrysler Concorde has climate control and behaves much the same way.
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'83 300D Turrrbo 295K miles |
#3
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Defrost is a system override like using high or low fan settings instead of automatic.
Mine does the same thing. I'm glad it does that so that I do not get an icy blast. BTW, I have to do vacuum work on the HVAC system. Air is split between all the dash vents and the windshield vents.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#4
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Replace your monovalve insert, it's likely wrinkled or torn, and isn't feeding much water through the heater core. On Defrost, you get high fan and full heat (Monovalve constantly energized), so the blower will run at 3/4 speed or something.
You will have very low speed fan and cold air (higher fan speed but still cold air on high fan) until the heater core warms up. Verify that the aux pump works, too, and that you are full on coolant. Also, if the thermostat is bad, it will take forever to heat up (you should run just above 80 C rather quickly). Peter
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1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#5
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Pretty close to normal.........the fan should not come on, in other than defrost, until the temp sensor on the thermostat housing senses warm coolant.
However, it does sound like you may have a fresh/recirc vacuum pod leaking. It's located behind the glove box, about $50 for a replacement.
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Sam 84 300SD 350K+ miles ( Blue Belle ) |
#6
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Quote:
I can leave the heat on all day and it will not turn on unless i hit defrost for a while then switch back to EC heat button then it might work. I must have bad climate control units, I will solder another one and try that. Mono valve is good also and so is the thermostat. Once it starts working it will work normal for the day. Is there another temperature sensor for heat other than the one on the T housing? Steve
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85 300d in progress |
#7
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From looking at the schematic, your temp. controller (mounted above the passenger footwell) may be temperamental. Or it may be an input to it such as the heater air temp. sensor or the in-car temp sensor. There is a connection between the temp. controller and the pushbutton control labelled "heating enable control" that controls power to the aux. pump. and, through circuitry, controls the mono-valve.
The pushbutton controller, for the most part, switches the modes but a lot of that is controlling the vacuum pods for air direction. But since it is mechanical relays and switches, it is prone to the most failures such as cracked solder joints.
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Sam 84 300SD 350K+ miles ( Blue Belle ) |
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