ac accumulater icing over on long drives
#1
08-04-2016, 11:48 AM
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ac accumulater icing over on long drives
Hey all,
Quick question. I was on a cross country road trip in my '86 F150 with a 1 year old AC system, and I noticed the ac performance would decrease after being on the road for a while. I popped the hood at a gas station and saw that the accumulator was all iced over so I went without AC for awhile and eventually turned it back on and it blew cold. I mentioned it to a mechanic and he said it'd be the AC Cycle Switch on the side of the accumulator. I have a new cycle switch, but before I threw it on there, I thought I'd ask you two questions.
1) do I need to have the R134A evacuated before I replace this switch
2) Does it sound like the problem I'm experiencing is likely due to a bad switch in the first place?
I appreciate any help. Thanks.
John
Quick question. I was on a cross country road trip in my '86 F150 with a 1 year old AC system, and I noticed the ac performance would decrease after being on the road for a while. I popped the hood at a gas station and saw that the accumulator was all iced over so I went without AC for awhile and eventually turned it back on and it blew cold. I mentioned it to a mechanic and he said it'd be the AC Cycle Switch on the side of the accumulator. I have a new cycle switch, but before I threw it on there, I thought I'd ask you two questions.
1) do I need to have the R134A evacuated before I replace this switch
2) Does it sound like the problem I'm experiencing is likely due to a bad switch in the first place?
I appreciate any help. Thanks.
John
#2
08-04-2016, 01:39 PM
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No need to evacuate the system. The switch screws in and pushes on a valve stem. Similar to your tires. AS far as the problem, it is one of the items you should look at. The system is not shutting down when the 134A is in vapor form and really cold. This is not normally the problem with these trucks from my experience. Usually, we have warm air from an inefficient condenser.
#3
08-04-2016, 02:15 PM
The switch regulates the cooling by cycling the compressor on and off. As the system gets colder, the pressure gets lower to the point the low pressure switch cycles the clutch off. With the warm air going over the coil the system eventually warms up and the pressure rises, and the switch cycles the system back on.
On a hot day the system usually doesn't cycle, but using the A/C on a moderate day it will cycle on and off. Sounds like yours didn't and it froze up. Replace the switch and see what happens.
On a hot day the system usually doesn't cycle, but using the A/C on a moderate day it will cycle on and off. Sounds like yours didn't and it froze up. Replace the switch and see what happens.
#4
08-04-2016, 10:03 PM
John, your most likely culprit is crud blocking the airflow through the evaporator. Leaves and other debris get trapped on the upstream face. You'd be amazed how much crud collects there.
It's been a while, but I think you can pull the fan motor for access. If not, it's not too bad to open the evaporator case, but the fan motor is easier.
After that, you might be slightly low on refrigerant, but I'd check for blocked evaporator airflow first.
It's been a while, but I think you can pull the fan motor for access. If not, it's not too bad to open the evaporator case, but the fan motor is easier.
After that, you might be slightly low on refrigerant, but I'd check for blocked evaporator airflow first.
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