A/C is freezing for 20 min, then goes hot
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Joined: Oct 2010
Posts: 16
A/C is freezing for 20 min, then goes hot
Charged A/C, got 40 psi during fill on cheapo gauge with can. Will run super cold for 15 min in park. Seems great in driveway.
When driving will sometimes kick in freezing for 15-20 min, then goes hot. This is pattern for over month - so leak seems unlikely. temp here is 95-100 & humid.
Have not run pressure test on high and low, and have not tested switches with multimeter. Have not watched the compressor for 15 min straight, just noted that at end of recharge, and other 15 min tests (in driveway), a/c was still freezing at the final min.
So far family, friends, and neighbors advice differs 100%, but each is 100% sure.
1. If runs real cold then goes hot after 15-20min then must be little low on r134.
2. Must be high pressure switch - didnt explain why - but based on my pattern was the typical cause in 98 blazers. Hate to loose charge just to see.
3. Low pressure switch - same vage reason. typical cause. try and see, no loss of charge
4. Thermostat is bad - (my temp is 150 always). Parts guy had said temp is too low for blazer, (agreed), and would result in the ac going hot if rad. coolant exceeds certain temp.
Just too damn poor to run to a/c shop, or replace parts for fun. Anyone had similar problem or know of common cause for the system to go hot??
Yet another tip from a die hard f150 guy...Said he's had several trucks with exact problem, which was caused by compressor clutch not re-engaging. Said to wait for the clutch to stop, wait and if it doesnt start again- tap with handle of tool - if starts again its freezing due to air gap. Remove bolt, regap to fac. spec, reinstall and presto. Said they all do it on used trucks..
When driving will sometimes kick in freezing for 15-20 min, then goes hot. This is pattern for over month - so leak seems unlikely. temp here is 95-100 & humid.
Have not run pressure test on high and low, and have not tested switches with multimeter. Have not watched the compressor for 15 min straight, just noted that at end of recharge, and other 15 min tests (in driveway), a/c was still freezing at the final min.
So far family, friends, and neighbors advice differs 100%, but each is 100% sure.
1. If runs real cold then goes hot after 15-20min then must be little low on r134.
2. Must be high pressure switch - didnt explain why - but based on my pattern was the typical cause in 98 blazers. Hate to loose charge just to see.
3. Low pressure switch - same vage reason. typical cause. try and see, no loss of charge
4. Thermostat is bad - (my temp is 150 always). Parts guy had said temp is too low for blazer, (agreed), and would result in the ac going hot if rad. coolant exceeds certain temp.
Just too damn poor to run to a/c shop, or replace parts for fun. Anyone had similar problem or know of common cause for the system to go hot??
Yet another tip from a die hard f150 guy...Said he's had several trucks with exact problem, which was caused by compressor clutch not re-engaging. Said to wait for the clutch to stop, wait and if it doesnt start again- tap with handle of tool - if starts again its freezing due to air gap. Remove bolt, regap to fac. spec, reinstall and presto. Said they all do it on used trucks..
Last edited by dbaas; Jul 23, 2011 at 02:40 PM. Reason: additional info
Junior Member
Joined: Apr 2006
Posts: 467
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A few possibilities. Next time it goes warm pop open the hood and see if the compressor is engaged or attempting to run.
If not - it could be the high side safety switch, the low side switch tripping on a short charge (might not be 40lbs anymore, if you needed to add there's a small leak somewhere). Could be your A/C clutch relay is getting fatigued and when it gets hot enough the contacts open. You could swap with a known good relay to check that. Could be a wiring connection getting flaky and when it gets hot enough - opens.
If the compressor is running and it goes hot could be your accumulator/dryer is plugged up with moisture and when the cabin gets cool enough and the returning refrigerant gets cold enough it's freezing the restricted dryer with a block of ice stopping the process. Also, when you turn the truck off after a few minutes (and the A/C has been running) do you notice a puddle on the ground under the passenger side firewall? You should in this humid weather, if not-the drain is plugged from your heater box and your evaporator in the heater box is plugging up from the ice forming from the water caught in it.
If not - it could be the high side safety switch, the low side switch tripping on a short charge (might not be 40lbs anymore, if you needed to add there's a small leak somewhere). Could be your A/C clutch relay is getting fatigued and when it gets hot enough the contacts open. You could swap with a known good relay to check that. Could be a wiring connection getting flaky and when it gets hot enough - opens.
If the compressor is running and it goes hot could be your accumulator/dryer is plugged up with moisture and when the cabin gets cool enough and the returning refrigerant gets cold enough it's freezing the restricted dryer with a block of ice stopping the process. Also, when you turn the truck off after a few minutes (and the A/C has been running) do you notice a puddle on the ground under the passenger side firewall? You should in this humid weather, if not-the drain is plugged from your heater box and your evaporator in the heater box is plugging up from the ice forming from the water caught in it.
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