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Maintenance & Repair Climate Control Problems (Air Conditioning, Heat) - All Cars
791 messages, Last post on Aug 12, 2009 at 12:55 PM
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the a/c uses something in the range of 10-15 HP to operate, depending on the size of the car and compressor. that is loading down your engine quite a bit, and the cooling system is not up to the task. what could it be? bad thermostat, dirt/bugs/guck blocking the radiator fins, bad fan motor or relay or dying fluid clutch, water pump marginal or worse, gutless coolant that is no longer a 50/50 mix due to age, internal blockages of the radiator, collapsed hose due to bad radiator cap... lots of things. a temporary aid is to put down the windows (so you don't die when you do the rest of this,) and turn the heater up full to act as an auxiliary radiator. but you will need to get after the real issue, which is the cooling system is not doing its job under stress. |
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| swschrad really covered it, for the most part. I'd start with coolant level and radiator cap, then go on to the rest. Don't be too surprised if you find the thermostat has been failing. | |
| My 1990 Toyota Celica loss most of its refrigerant and this triggered the auto-off sensor. I have refilled the air conditioner refrigerant but I do not know how to reset this sensor. Any help? | |
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This is a friends car. I got this info from his wife. I'll get to him tomorrow for a better explanation Anyway, the problem appeared to be the AC switching from vents to defrost intermittantly. Actual problem seems to be (per dealer) the AC reversing somehow, and sucking air back into the engine?? Doea any of this make sense (I really need to get a better explanation). ANyway, dealer was stumped, and actually decided to replace the engine! Chrysler corp. seems to have come up with another possibility that involves replaceing some sort of module. I will try to get a better explanation and post it tomorrow, but any initial thoughts will be appreciated. |
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| swschrad sugested to boslaw1 to change the thermostat but I think that bad thermostat would cause overheating with or without A/C on. After starting the engine, the temperature would rise constantly. Why would the thermostat fail only with the A/C on? Maybe I am wrong but anybody can explain this? | |
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| Sometimes when thermostats fail they are closed and no coolant can flow. Other times they are stuck wide open, and never even slow down the coolant. A failed thermostat that is partially closed and therefore partially open could let enough coolant go by to be adequate when the A/C is off, but not so when it is on. | |
| Thanks. I didn`t think about this third possibility. | |
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how in heck is the a/c going to run backwards? the compressor sure isn't, and the vapor phase isn't going to run backwards. it would seem to be impossible for the fan to run backwards since there is not a source of -12 volts anywhere to leak across a failed computer module output device and spin the fan backwards. I would suspect what's going on is the damper door system is not working according to hoyle. as for sucking air into the engine compartment... nah. not unless somebody took the input manifold hose off the air cleaner and took out the fan motor and duct-taped the hose into that big old hole. bad communications here from the shop. |
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When the coolant system is new there is a 30% reserve designed to allow idle in gear in 100F traffic AC on. All car designs are tested some have even more reserve. Some may have a time limit assuming 15-30 minutes worse case traffic in 100F others like Mercedes can idle in gear for 12 hours due to large rad and 15 quarts of coolant. Most non lux cars have around 10 quarts or less Every year approximately 5% disappears due to radiator external corrosion and fin bending blockages from dirt, etc. Poor internal coolantant maintenance can accelerate this loss of reserve. Normally the correct thing to do is replace the radiator at around 5-6-7 years [examine the AC condensor for bent fins, dirt blockages, corrosion not shiny anymore as this may need changing out to restore as new performance [help AC cooling also]. Be careful about non oem cheapo rads as they are only warranteed for 12/12 they use thinner metal fewer fins and inexpensive construction {weigh them] they may not provide oem reserve when brand new and age very rapidly! Made primarily for people who need to fix to sell a car.....there are quality replacements out there but you must examine them closely [always ask if there is a better quality unit available than the offered unit as most shops buy cheap to help the customer who complains about costs. A factory unit may be $400 retail and cost dealer $200, a cheapo aftermarket may cost shop $90-115 and a premium unit available for $145-165-175 [shop cost]. |
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I got a more exact description from the owner. Anything here ring a bell? When I have the A/C on at bi-level or just on my face it changes direction to the defrost vents when I accelerate the truck and get to 2k RPM's & around 40 mph. Once I let off the gas and the speed dials drop, the air goes back to the settings they were supposed to be at. The Dodge dealer originally thought that the problem was my "A/C Vacuum Resevoir". Can't remember the exact makeup of it, but anyway it still had a problem after they fixed that. So that's when they said: "Replace the engine" They then called and said they'd like to try to install a second check valve to help keep the air from changing vents? I have no idea how that would help.
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