My 1993 mr2 has ice cold air at idle and when driving around town but as soon as I get above 50 mph or so in 5th gear the compressor stops cycling and the air gets warm. I think the system pressure is low. The system had not been messed with since 2010 when it was converted to r134a.
Air conditioning only cold at low speed/idle
- Thread starter TinyVoices
- Start date
- Status
I had the same problem once. It was low on refrigerant - shop said it had only about half the refrigerant it was supposed to. Find the leak, fix it, and recharge.
Umm, no. If it has enough refrigerant to get cold once, it can do it again.
Compressor stops engaging is often because the clutch gap is too large. The electromagnet coil gets weaker as it heats up.
Old Toyotas also have an "A/C Amplifier" module which is prone to bad connections or other internal failures. When it stops cooling, is the A/C light on the dash blinking? That means that the Amplifier has decided to lock out the compressor.
Compressor stops engaging is often because the clutch gap is too large. The electromagnet coil gets weaker as it heats up.
Old Toyotas also have an "A/C Amplifier" module which is prone to bad connections or other internal failures. When it stops cooling, is the A/C light on the dash blinking? That means that the Amplifier has decided to lock out the compressor.
Last edited:
Originally Posted By: mk378
Umm, no. If it has enough refrigerant to get cold once, it can do it again.
Compressor stops engaging is often because the clutch gap is too large. The electromagnet coil gets weaker as it heats up.
Old Toyotas also have an "A/C Amplifier" module which is prone to bad connections or other internal failures. When it stops cooling, is the A/C light on the dash blinking? That means that the Amplifier has decided to lock out the compressor.
There is no light blinking and I don't believe the car even has an a/c light.
I should also mention the compressor was replaced with a modern one in 2010.
Umm, no. If it has enough refrigerant to get cold once, it can do it again.
Compressor stops engaging is often because the clutch gap is too large. The electromagnet coil gets weaker as it heats up.
Old Toyotas also have an "A/C Amplifier" module which is prone to bad connections or other internal failures. When it stops cooling, is the A/C light on the dash blinking? That means that the Amplifier has decided to lock out the compressor.
There is no light blinking and I don't believe the car even has an a/c light.
I should also mention the compressor was replaced with a modern one in 2010.
Last edited:
Bud_One
Site Donor 2025
I had the same issue on my 99 Civic Coupe...ended up being the expansion valve.
JHZR2
Staff member
Interesting comment about the clutch gap. I was thinking sort of the opposite - at high engine speeds could the compressor be "sucking down" a relatively low charge causing the low pressure lockout to actuate?
The OE thing I'd never do, particularly on a retrofit, is assume its low, even with a pressure reading indication, and add gas. Retrofits done properly can work reasonably well, but should be recharged with the appropriate mass of refrigerant calculated based upon the original R-12 charge and any changes made to the system.
An MR-2 is a pretty tiny car and shouldn't take a lot to get cold air.
The OE thing I'd never do, particularly on a retrofit, is assume its low, even with a pressure reading indication, and add gas. Retrofits done properly can work reasonably well, but should be recharged with the appropriate mass of refrigerant calculated based upon the original R-12 charge and any changes made to the system.
An MR-2 is a pretty tiny car and shouldn't take a lot to get cold air.
Originally Posted By: TinyVoices
The system had not been messed with since 2010 when it was converted to r134a.
This is the key.
If you are not comfortable working on AC, then bring it to a mechanic that can properly measure the pressure and identify the leaks if any.
As easy maintenance, may be clean the condenser/radiator stack and also the evaporator behind the fan.
Although, I suspect, something is leaking with that 17 years age system or the compressor is about to seize or weak.
17 years is a good life by any standard, unfortunately, parts do not last that long anymore.
At the least, there are something internally that needs cleaning.
The system had not been messed with since 2010 when it was converted to r134a.
This is the key.
If you are not comfortable working on AC, then bring it to a mechanic that can properly measure the pressure and identify the leaks if any.
As easy maintenance, may be clean the condenser/radiator stack and also the evaporator behind the fan.
Although, I suspect, something is leaking with that 17 years age system or the compressor is about to seize or weak.
17 years is a good life by any standard, unfortunately, parts do not last that long anymore.
At the least, there are something internally that needs cleaning.
Probably undercharged.Hook it up to some AC gauges and watch the pressure drop when giving the engine some steady rpms. Hold at 2000rpm or so and test low side pressure.Dont hold the freon can upside down when charging and dont charge from the high pressure side.
I agree with low charge.
Are you sure it's not staying engaged and freezing the evaporator? Same symptoms of warm air but a completely different cause.
My cause was self-inflicted, but you never know. I fitted an auxiliary pusher fan to my condenser a while back. I wired it in parallel with the compressor powering both of them from an additional relay to take the load of the main harness. I struggled for months with the system getting warm at speed. It eventually turned out above about 80 KP/H the pusher fan made a very nice generator and was making enough current to keep the compressor engaged causing evaporator icing.
Symptoms were it was fine around town, but as soon as I hit the freeway for any length of time it would get warmer and warmer until I got back into traffic when it would slowly cool down again.
My cause was self-inflicted, but you never know. I fitted an auxiliary pusher fan to my condenser a while back. I wired it in parallel with the compressor powering both of them from an additional relay to take the load of the main harness. I struggled for months with the system getting warm at speed. It eventually turned out above about 80 KP/H the pusher fan made a very nice generator and was making enough current to keep the compressor engaged causing evaporator icing.
Symptoms were it was fine around town, but as soon as I hit the freeway for any length of time it would get warmer and warmer until I got back into traffic when it would slowly cool down again.
- Status
Similar threads
