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Interesting AC problem
Very weird, the AC will intermittently blast me with hot air, but only when I come to a stop at a light and idle for a minute or two, never when rolling down the road. After a minute when the AC has cooled off the heater core again do I get cool air.
I'm thinking bad monovalve or bad monovalve ground in the ACC unit, but why do you think it's only happening at idle and then fixing itself at speed? Thanks!
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cbjukraine '84 300D |
#2
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My guess is torn mono valve, and poor ac performance from r134 conversion.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
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Quote:
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2001 SLK 320 six speed manual 2014 Porsche Cayenne six speed manual Annoy a Liberal, Read the Constitution |
#4
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Heat on = mono valve passing coolant. Should be off when A/C is on. You can test by feeling the solenoid "thunk" when +12 is applied. At this age, it's common to find a torn rubber diaphragm inside, as well. Variable cooling = poor A/C performance. Best A/C conditions require compressor rpm AND a good airflow across the condenser. You have neither when idling. Larry suggested checking the hose that siphons air over to the ambient temp sensor. These hoses degrade over time and as a result, the sampling air comes from inside the dash.... However, since you're getting cold air when moving, I think your problem lies elsewhere. There are a number of possibilities for your A/C issues. Electric fan not coming on. Poor conversion.... Moisture in system Receiver dryer not working System not vacuumed before conversion gas installed Did not install R-134A throttle valve (controls liquid flow to evap) When poor performnce is encoutered, it's best to back up and start again, replacing the receiver/drier and the throttle valve (if not already done). A complete system vacuum, running for at least an hour, then shut off pump and close valves and moniter vacuum. Any loss requires additional work before the system will be good. Also consider the oil. Whenever you replace a component in the A/C system, a certain amount of oil will be lost. This must be replaced. then there is the type of oil to use, search the archives for lots of opinions... R-134a backfits typically take 85% of an R-12 fill. R-134a systems are very sensitive to fill amounts. With R-12 you got a sinusoidal wave type of cooling graph (gradually increase cooling effect as charge increases) whereas R-134a operates more as a step function (nothing, nothing, nothing, bang! cooling!). I've found it very consistent to monitor low pressure vapor return line for temperature. When you approach the correct amount of R-134a, you can feel a noticable drop in the return temperature. Also, on the W123 cars, this return line runs right across the front of engine, uninsulated. For my W123 cars, I used a piece of pipe insulation to cover return line, to ensure a cooler compressor inlet temp. Good luck! Jim
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14 E250 BlueTEC black. 45k miles 95 E320 Cabriolet Emerald green 66k miles 94 E320 Cabriolet Emerald green 152k miles 85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles |
#5
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That is not correct. Unless MIN is selected on the temperature control, the ACC uses heat to regulate temperature, so it is entirely normal for the monovalve to be operating concurrent with the a/c.
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
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Agreed, the A/C part still stands. I had assumed he was already on min because of the A/C issue. Bad assumption on my part, and worse to have not specified it when suggesting a solution... Jim
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14 E250 BlueTEC black. 45k miles 95 E320 Cabriolet Emerald green 66k miles 94 E320 Cabriolet Emerald green 152k miles 85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles |
#7
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If the "hot air" is hotter than ambient in cabin, it must be from the heater. Try clamping off the heater hose from the head, near oil filter. This assumes your temp dial has been set to "min".
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