Please help....
Please help....
Hi everyone- I have an issue with my 98 F150XL 4.2.... the AC began working intermittently, blowing cold sometimes and then warm. In parallel, my truck would always seem to want to stall out when idling with the AC on. After approx 2 months of this the Ac is not blowing cold at all. The heat is working and I can control the temp of the heat but when I turn the dial to cold I just get warm air. I have charged the AC and there is no leak. I have verified the clutch is kicking on and can hear the compressor engage. I have checked the fuses and they are all good. My truck has 325k miles on it but she runs like a top and I’ve had no mechanical issues unrelated to what I’ve just mentioned. Any help is much appreciated!
Thank you sir- I bought a new actuator and blend door and will install today or tomorrow. If that’s not the issue then I’ll just begin replacing everything I suppose because after 325k miles, everything should be about ready to fail. Thanks for your support!
Senior Member
Joined: Oct 2002
Posts: 7,295
Likes: 125
From: St. Louis (Out in the woods)
Put the tools down for a bit, they're premature. You do not yet know what is actually at fault.
If it were the blend door or actuator, temperature control on the heat side would also be wacked out. Since that is working, turn your attention back to the refrigeration system and make sure it is actually working, not just appearing to go through the motions.
Verify the compressor clutch is actually spinning the shaft of the compressor when the clutch plate pulls in and stays in for more than a few seconds. If so, then feel the refrigerant lines at the firewall to see whether or not they get cold.
Report observations. FWIW, at 325K, it's far more likely you may have a worn out compressor clutch that hasn't been properly diagnosed.
As for the stalling, it's usually caused by either a sticky IAC valve (those usually manifest at the onset of cool or cold weather) or a large intake or PCV vacuum leak.
If it were the blend door or actuator, temperature control on the heat side would also be wacked out. Since that is working, turn your attention back to the refrigeration system and make sure it is actually working, not just appearing to go through the motions.
Verify the compressor clutch is actually spinning the shaft of the compressor when the clutch plate pulls in and stays in for more than a few seconds. If so, then feel the refrigerant lines at the firewall to see whether or not they get cold.
Report observations. FWIW, at 325K, it's far more likely you may have a worn out compressor clutch that hasn't been properly diagnosed.
As for the stalling, it's usually caused by either a sticky IAC valve (those usually manifest at the onset of cool or cold weather) or a large intake or PCV vacuum leak.
Last edited by projectSHO89; Mar 23, 2021 at 11:29 AM.
Member
Joined: Apr 2016
Posts: 29
Likes: 2
From: NW Georgia (over yonder)
Ah, Air conditioning. As you're here, I'm going to say it's a safe bet there's more info you need to make an accurate diagnosis. Let me help. Keep in mind, You got a LONG list to check off to make it work good. In case you haven't already fixed it or taken to a shop; here's some clues and tips.
A/C is a belt driven pump that pumps against a bottle neck. In order for the system to work; you have to have-
1) Air passing through the condenser (check your fan clutch, make sure it can push enough air through it)
2) Air passing through the evaporator (your blower motor needs full capacity here and your blend doors need to work)
3) Freon pressure high enough on the low side that it doesn't freeze the compressor's PAG oil. (should be 40 PSI with the compressor spinning and the blower motor on high and blend doors on fresh)
4) Freon pressure low enough on the high side that it doesn't blow the system to shreds (should be around 200-220PSI; NO HIGHER THAN 270; with the compressor spinning and the fan clutch spinning. (Note: at idle, the fan clutch should spin the radiator fan at the same speed as the belt pulley it is attached to +/- 50RPM; if it's any lower than that, install new one)
5) A really good alternator and a fully charged battery- A/C system in your truck under normal circumstances should pull 27 AMPS all by itself.
6) The Water content of your Freon needs to be lower than 5% otherwise it will freeze on the low side of your system and cause blockages; this is why shops vacuum down systems for half an hour before recharging them.
7) Operational control valves and switches. The "bottleneck" is actually referred to in Ford terms as an "Orifice Tube" OR an "Expansion Valve" depending on the model, but both do the same thing. When the Freon passes through the bottleneck, it changes temperature as it passes through, and as the temperature changes, the "valve" closes or opens depending on the predetermined/engineered amount of BTU change across it for a given amount of Freon passed within a pre-determined time frame. As this bottleneck ages, it becomes less accurate. Expansion valves become more "pass-through", which prevents pressure building on the high side, so the system "works" but never gets cold. Orifice tubes, on the other hand, get clogged, and become, well, blockages, and cause the pressure on the high side to build hilariously high and fast without reopening, causing a system that gets cold very quickly and then warm, and then cold, and then warm, and then cold. Both cases, it ruins the other parts of the system and to that end, there are VERY VERY good reasons why A/C Compressor today are sold on the strict understanding that your Compressor warranty is ONLY valid if you can prove that you also installed a new Orifice Tube/Expansion Valve; because not doing so will allow the pressure to vary so wildly that it can bust the brand-new scrolls inside.
8) Relays. You have two A/C relays. One is A/C Compressor Relay. This one is "ON" for the compressor and it sends the 12V+ signal for the compressor to engage; it gets its signal by the switch on the dash. The other is the A/C Cut-Out Relay. This one is interrupts the other circuit and it is computer controlled to turn the A/C compressor off for ANY REASON ON ITS PREDETERMINED LIST. I don't know what yours is exactly, but A/C Cut-Out tends to be- A) High Side Pressure above 400PSI; B) Low Side Pressure below 18PSI; C) Engine Coolant Temperature ABOVE 245 degrees (rad cap busts off at 257); D) Engine Speed higher than 4500 RPM for longer than 12 seconds; E) Engine Speed lower than 500 RPM for longer than 4 seconds; F) Full-Throttle for longer than 18 seconds; G) System voltage below 11.5 volts for longer than 3 minutes.
Now. After all of the list above; here's my suggestion. If you're D.I.Y.'ing this, get yourself a real gaugeset; and i'm not talking about that stupid freon can with the built in gauge; that only tells 1/8 of the story. I'm talking a REAL FREON GaugeSet. One that allows you to read Low and High.
Step 1 Start COLD: (ENGINE OFF)
Read your pressures with everything cold before you even start the engine for the day. For yours, the system inactive, cold, pressure should read roughly 95 PSI on both sides with everything turned off and the system cold. If the pressures are different; go no further and seek professional advice.
Step 2: Check Fan Clutch: (ENGINE OFF)
Your Fan Clutch should have no play fore-and-aft, but as it's "cold" it should spin somewhat freely, but not like it's not attached. A correct fan clutch should spin free for a half to a full rotation after being spun by hand, and then slow down almost immediately like someone put the brakes on it. If it spins more than five full rotations after spinning it by hand; replace the fan clutch with a NEW ONE. Don't cheap out here; you'll thank me later. Also, don't think that just because the truck's not running hot that you can get away with skipping this step. The condenser puts out nearly the same number of BTU's that the radiator gives off; this part working properly is ESSENTIAL for the A/C to work.
Step 3: Check Condenser Fins for Blockages: (ENGINE OFF)
I cannot tell you how many times I find pine-needles and acorns on the core support right in front of the A/C condenser here in Atlanta. I've pulled straw, plastic bags, bird feathers, road rocks/gravel, Gary Busey, pages from the real yellow pages; all out from A/C condensers that weren't flowing properly. I tell ya, pulling Gary Busey out of an A/C condenser was a tough one, lemme tell ya; but I managed.... Point is, it's gotta be clean, and it's gotta flow air. It just has to. If it doesn't, everything else you try will be in vain.
Step 4: Check High/Low Pressure Differential: (ENGINE ON)
Start engine, and let it idle, and turn A/C to MAX, FULL BLOWER MOTOR. Throughout this test we are testing at idle speed. Watch the pressures change as the compressor kicks on. The low side should drop to its lowest point slowly. If the compressor kicks off before the low side drops below 40, check your idle speed to see if it's high enough; your truck should idle at 750-850 (if memory serves me right), and it shouldn't drop more than 100 RPM when the compressor engages. If it's working properly, it'll drop to 30 PSI and hover around 30-40 and stay there the entire time the compressor is on. Also watch the high side, it should only rise to 220 or so, and that should happen the same time it drops on the low side to 30. If the low side drops to 30 and the high side continues to climb, that means that the condenser is not able to release heat quickly enough; (this is why we checked the fan clutch earlier and cleaned the fins). Make sure the compressor turns off on its own if the high side rises above the cut off (I think it's like 310-320 PSI on the high side on yours if I remember right). If the low side drops below 18 and the compressor doesn't cut off, STOP THE ENGINE IMMEDIATELY, and find out WHY. If the high side rises above 330 PSI on the high side at any point, STOP THE ENGINE IMMEDIATELY, and find out WHY.
If after performing this test you have a low side of 30 and a high side of roughly 220-250 sustained, you should have cold air coming out of the vents after a minute or two; if it doesn't your problem is in the dash; ergo, blend door issue or the fins of the evap core has dirt/dust/Joe Pesci in it. Side note: If Joe Pesci is in your F150's evap core, seek professional help immediately.
If everything I've written above has scared you; then well, maybe it's best you let an A/C guy or your trusted mechanic to handle this for you; you can do it, don't get me wrong, but it's a complex system with a steep learning curve; it's not for everybody, and it's a thinking man's game; and there's no shame in letting someone else work on it that has the answer already. If on the other hand, you have a thinking man's mentality, or are inquisitive and/or careful/resourceful, or are Gary Busey (or any combination thereof); you may be able to do this, and can tackle it if you have the proper tools.
Good luck.
A/C is a belt driven pump that pumps against a bottle neck. In order for the system to work; you have to have-
1) Air passing through the condenser (check your fan clutch, make sure it can push enough air through it)
2) Air passing through the evaporator (your blower motor needs full capacity here and your blend doors need to work)
3) Freon pressure high enough on the low side that it doesn't freeze the compressor's PAG oil. (should be 40 PSI with the compressor spinning and the blower motor on high and blend doors on fresh)
4) Freon pressure low enough on the high side that it doesn't blow the system to shreds (should be around 200-220PSI; NO HIGHER THAN 270; with the compressor spinning and the fan clutch spinning. (Note: at idle, the fan clutch should spin the radiator fan at the same speed as the belt pulley it is attached to +/- 50RPM; if it's any lower than that, install new one)
5) A really good alternator and a fully charged battery- A/C system in your truck under normal circumstances should pull 27 AMPS all by itself.
6) The Water content of your Freon needs to be lower than 5% otherwise it will freeze on the low side of your system and cause blockages; this is why shops vacuum down systems for half an hour before recharging them.
7) Operational control valves and switches. The "bottleneck" is actually referred to in Ford terms as an "Orifice Tube" OR an "Expansion Valve" depending on the model, but both do the same thing. When the Freon passes through the bottleneck, it changes temperature as it passes through, and as the temperature changes, the "valve" closes or opens depending on the predetermined/engineered amount of BTU change across it for a given amount of Freon passed within a pre-determined time frame. As this bottleneck ages, it becomes less accurate. Expansion valves become more "pass-through", which prevents pressure building on the high side, so the system "works" but never gets cold. Orifice tubes, on the other hand, get clogged, and become, well, blockages, and cause the pressure on the high side to build hilariously high and fast without reopening, causing a system that gets cold very quickly and then warm, and then cold, and then warm, and then cold. Both cases, it ruins the other parts of the system and to that end, there are VERY VERY good reasons why A/C Compressor today are sold on the strict understanding that your Compressor warranty is ONLY valid if you can prove that you also installed a new Orifice Tube/Expansion Valve; because not doing so will allow the pressure to vary so wildly that it can bust the brand-new scrolls inside.
8) Relays. You have two A/C relays. One is A/C Compressor Relay. This one is "ON" for the compressor and it sends the 12V+ signal for the compressor to engage; it gets its signal by the switch on the dash. The other is the A/C Cut-Out Relay. This one is interrupts the other circuit and it is computer controlled to turn the A/C compressor off for ANY REASON ON ITS PREDETERMINED LIST. I don't know what yours is exactly, but A/C Cut-Out tends to be- A) High Side Pressure above 400PSI; B) Low Side Pressure below 18PSI; C) Engine Coolant Temperature ABOVE 245 degrees (rad cap busts off at 257); D) Engine Speed higher than 4500 RPM for longer than 12 seconds; E) Engine Speed lower than 500 RPM for longer than 4 seconds; F) Full-Throttle for longer than 18 seconds; G) System voltage below 11.5 volts for longer than 3 minutes.
Now. After all of the list above; here's my suggestion. If you're D.I.Y.'ing this, get yourself a real gaugeset; and i'm not talking about that stupid freon can with the built in gauge; that only tells 1/8 of the story. I'm talking a REAL FREON GaugeSet. One that allows you to read Low and High.
Step 1 Start COLD: (ENGINE OFF)
Read your pressures with everything cold before you even start the engine for the day. For yours, the system inactive, cold, pressure should read roughly 95 PSI on both sides with everything turned off and the system cold. If the pressures are different; go no further and seek professional advice.
Step 2: Check Fan Clutch: (ENGINE OFF)
Your Fan Clutch should have no play fore-and-aft, but as it's "cold" it should spin somewhat freely, but not like it's not attached. A correct fan clutch should spin free for a half to a full rotation after being spun by hand, and then slow down almost immediately like someone put the brakes on it. If it spins more than five full rotations after spinning it by hand; replace the fan clutch with a NEW ONE. Don't cheap out here; you'll thank me later. Also, don't think that just because the truck's not running hot that you can get away with skipping this step. The condenser puts out nearly the same number of BTU's that the radiator gives off; this part working properly is ESSENTIAL for the A/C to work.
Step 3: Check Condenser Fins for Blockages: (ENGINE OFF)
I cannot tell you how many times I find pine-needles and acorns on the core support right in front of the A/C condenser here in Atlanta. I've pulled straw, plastic bags, bird feathers, road rocks/gravel, Gary Busey, pages from the real yellow pages; all out from A/C condensers that weren't flowing properly. I tell ya, pulling Gary Busey out of an A/C condenser was a tough one, lemme tell ya; but I managed.... Point is, it's gotta be clean, and it's gotta flow air. It just has to. If it doesn't, everything else you try will be in vain.
Step 4: Check High/Low Pressure Differential: (ENGINE ON)
Start engine, and let it idle, and turn A/C to MAX, FULL BLOWER MOTOR. Throughout this test we are testing at idle speed. Watch the pressures change as the compressor kicks on. The low side should drop to its lowest point slowly. If the compressor kicks off before the low side drops below 40, check your idle speed to see if it's high enough; your truck should idle at 750-850 (if memory serves me right), and it shouldn't drop more than 100 RPM when the compressor engages. If it's working properly, it'll drop to 30 PSI and hover around 30-40 and stay there the entire time the compressor is on. Also watch the high side, it should only rise to 220 or so, and that should happen the same time it drops on the low side to 30. If the low side drops to 30 and the high side continues to climb, that means that the condenser is not able to release heat quickly enough; (this is why we checked the fan clutch earlier and cleaned the fins). Make sure the compressor turns off on its own if the high side rises above the cut off (I think it's like 310-320 PSI on the high side on yours if I remember right). If the low side drops below 18 and the compressor doesn't cut off, STOP THE ENGINE IMMEDIATELY, and find out WHY. If the high side rises above 330 PSI on the high side at any point, STOP THE ENGINE IMMEDIATELY, and find out WHY.
If after performing this test you have a low side of 30 and a high side of roughly 220-250 sustained, you should have cold air coming out of the vents after a minute or two; if it doesn't your problem is in the dash; ergo, blend door issue or the fins of the evap core has dirt/dust/Joe Pesci in it. Side note: If Joe Pesci is in your F150's evap core, seek professional help immediately.
If everything I've written above has scared you; then well, maybe it's best you let an A/C guy or your trusted mechanic to handle this for you; you can do it, don't get me wrong, but it's a complex system with a steep learning curve; it's not for everybody, and it's a thinking man's game; and there's no shame in letting someone else work on it that has the answer already. If on the other hand, you have a thinking man's mentality, or are inquisitive and/or careful/resourceful, or are Gary Busey (or any combination thereof); you may be able to do this, and can tackle it if you have the proper tools.
Good luck.