1993 400E. A/C will not come on for maybe 30 to 45 minutes of driving and the engine and engine compartment gets really hot. Sometimes it comes on by itself and other times I have to restart the engine. When it does come on, it blows normal and the air is cold. Almost sounds like the heat is causing expansion of something until contact is made and it starts working again. When engine cools down, no a/c until things heat up again. I'm lost on this one. Maybe it's a wiring issue, but all mechanics want to do is to rebuild the HVAC system which is costly. Any thoughts would be helpful.
Mystery 400E A/C Issue
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There are a lot of basic checks that should be done, for example, the correct function of the low pressure switch on the reciever dryer, the engine temperature sensor, the amount of refrigerant in the system.
Aside from these, if you have an intermittent A/C system, you need to rule out the ignition switch as a possible cause. Also, consider that the system is designed to shut off the system when certain conditions exist. One of them is high engine temperature, another is a slow compressor due to a slipping serpentine belt.
Aside from these, if you have an intermittent A/C system, you need to rule out the ignition switch as a possible cause. Also, consider that the system is designed to shut off the system when certain conditions exist. One of them is high engine temperature, another is a slow compressor due to a slipping serpentine belt.
2014 G550, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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Hmmm, seems like the system pressure may be borderline low. When things get hot, the refrigerant expands and the pressure increases to the point where the low pressure cut-out switch allows the system to run. Check or have the pressures checked.
2014 G550, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,971 Posts
On the receiver/dryer. There are two of them. One is a pressure switch that turns on the cooling fans when the refrigerant is compressed to "working" pressure. The other is a high-low pressure switch that keeps the A/C from working the if refrigerant system pressure is either too low or too high. They are different colors and I can't remember which is which.
The red switch is the high pressure switch. The one on the opposite side is for low pressure. If you jump the two wires from the low pressure switch together with a paper clip or suitable jumper, you will be telling the system there is enough refrigerant in the system and the compressor will start once you start the engine and select an A/C mode. If it does, then yes, you either have low refrigerant or a bad switch.
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