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plsmoothy
User
May 9, 2008, 6:38 PM
Post #1 of 4
(3932 views)
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AC causing odd symptoms
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I own a '98 Mazda 626 with 130,000 miles. I'm hoping someone out there can shed some light on this situation. Its important to note that the following symptoms occur only when the AC is on and the car is in stop and go traffic. The car runs fine when the AC is not engaged or when the AC is on under highway conditions 1. car loses approximately 5-7 hundred rpm when the AC cycles on. Is this high? 2. I live in Southern California. The summers are hot. After driving the car in stop and go traffic I'll come to a stop (at a light for instance) and the idle speed will drastically fluctuate between the normal idle speed of approximately 7-8 hundred rpm to almost 0. In other words the car will almost stall. If I turn off the AC compressor the fluctuating stops. 3. When it gets to that point, the AC will stop cooling and the car will almost overheat. Again, these symptoms occur only when the AC is on and the car is in stop and go traffic. Any help is greatly appreciated.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 9, 2008, 10:33 PM
Post #2 of 4
(3929 views)
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Re: AC causing odd symptoms
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Idle speed should automatically compensate for the load of A/C which it isn't or the load is too much which is unknown right now.
I'm guessing that the fans are not coming on with the A/C request as they should and temps go too high and load of A/C is just insult to injury.
Do fans come on? Have to approach that first as the added heat without them makes the compressor work like crazy adding yet more heat so confuses the issue for now,
T
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plsmoothy
User
May 26, 2008, 8:57 PM
Post #3 of 4
(3885 views)
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Re: AC causing odd symptoms
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Thanks for the reply. I've been monitoring the cooling fans and only one is working. It's a dual fan system. The AC fan (passenger side) comes on when I turn on the AC but the radiator cooling fan (drivers side) never cycles on. Does that mean that the fan itself is broken or could the problem lie somewhere else? Also, I recently added freon to the cooling system. I did it myself with a home kit. If the pressure in the system in incorrect, would it create a larger load? Thanks again for your help.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 27, 2008, 1:47 AM
Post #4 of 4
(3882 views)
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98 Mazda 626 A/C Specs
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98 Mazda 626 Refrigerant and Lubrication specs:
Refrigerant - 134a, 28.5 ounces
Oil - 8 ounces PAG-100 viscosity
Always refer to underhood decals when available.
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Ok: You've added something from a kit which is now the likely problem. I need to know if the fan that doesn't come on in front of you also cools the condenser - it may be just for the engine's radiator and just might not be needed while you watch by chance but temp should stay stable.
Why did you add refrigerant? No doubt because A/C didn't cool well or at all - right? Now we need to know what the pressure was with compressor running and fan for condenser on before you added refrigerant and the pressure now after you added whatever was in that product - please find it and read what's in it - it probably has more than just the specific products listed above and nothing but those should ever be introduced to a system.
If too much was added there would be an extraordinary load on compressor up to and including locking it up which could seize it, squeel the belt, stall the engine but should have shut down compressor with high side pressures above perhaps 350 via the high side pressure switch then last ditch is a blowout valve.
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If the non working fan is in line to cool the condenser and not working the pressures would go sky high and load the engine perhaps beyond the range of idle speed controls to compensate normal loads.
BOTH pressures are needed especially now or evacuate the system and add just the specified amount of refrigerant within an ounce of that amount listed. Only minimal oil is lost over time or when system is just evacuated so don't add oil until known called for as there is no dipstick for oil amounts short of flushing all out and starting from empty. Gauges do NOT tell you how much product is in the system but do tell you what is happening which may or may not involve the actual charge of refrigerant when off spec.
So please let us know teh history of what compelled doing anything, what was added so we can have a baseline to diagnose what is wrong now.
Note: When A/C is off and compressor is not engaged there is little or no impact on engine operation.......
T
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