Odd behavior in HVAC system.

[flip]

Based on the description this is a function baked into the system. If you run on recirc for a certain period of time, it will automatically switch the blend door to outside air. I think they incorporated this after the explorer issue with exhaust getting pulled in through some hatch vents and continually recirculating high CO in the cabins. The fix was replacing the vents, exhaust tip redesign and software update to the HVAC module that forced it out of recirc after a set time.

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[Deleted member 3063]

This truck is turning out to be a peice of shit. Im starting to feel dumb for staying on board with my order.

you would be correct on the latter.

 

[da_jokker]

I wonder if, since you're on the lowest fan speed, it's sensing the evaporator start to freeze up so it's increasing airflow to prevent that from happening.

I thought that is controlled with the AC clutch. When the evap gets too cold, the AC clutch disengages for a few. Increasing and decreasing a fan to try and compensate seems like a stupid engineering design.

Of course that doesn't mean ford didn't do it

 

[evilletruck]

Yes have had this happen on several occasions, and its not when its set on auto or anything it just randomly happens.

 

[Southern Girl]

I thought my level 1 fan was about a 3 the other day. It was weird. I assumed it was because I had it set on Snow Miser temp and it was sunny, hot and humid that day?

 

[ffdemoss]

This?

Note:Recirculated air may turn off automatically, or prevent you from switching on in all air flow modes except MAX A/C to reduce the risk of fogging. Recirculation may also turn on and off automatically in various air distribution control combinations to improve heating or cooling efficiency.

 

[kurkowski41]

I thought that is controlled with the AC clutch. When the evap gets too cold, the AC clutch disengages for a few. Increasing and decreasing a fan to try and compensate seems like a stupid engineering design.

Of course that doesn't mean ford didn't do it

I know that system pressures are controlled by disengaging the clutch, but I don't know of a vehicle that regulates the temp of the evaporator that way. I've been around vehicles that the AC works well enough to freeze the evaporator, and the way to prevent it is more fan speed, because there's no way to control the compressor clutch. I just wondered if this one does it automatically. Seems to me like you always want the evaporator as cold as you can get it

 

[da_jokker]

I know that system pressures are controlled by disengaging the clutch, but I don't know of a vehicle that regulates the temp of the evaporator that way. I've been around vehicles that the AC works well enough to freeze the evaporator, and the way to prevent it is more fan speed, because there's no way to control the compressor clutch. I just wondered if this one does it automatically. Seems to me like you always want the evaporator as cold as you can get it

Interesting. When I got my Jeep XJ, the AC didn't work. Compressor wouldn't turn on. Put it in the shop to diagnose and turned put the temp sensor on the evaporator went out. To they replaced it, and the compressor clutch started working again.

During that process, they explained that without the sensor, the system couldn't tell how cold the evap was and if it freezes, it can damage the system (pressure buildup).. so the sensor is set to a certain temp, and when the thing gets too cold, it turns off the clutch for just a bit.

But that was of course and old system and a Jeep.

 

[ffdemoss]

I know that system pressures are controlled by disengaging the clutch, but I don't know of a vehicle that regulates the temp of the evaporator that way. I've been around vehicles that the AC works well enough to freeze the evaporator, and the way to prevent it is more fan speed, because there's no way to control the compressor clutch. I just wondered if this one does it automatically. Seems to me like you always want the evaporator as cold as you can get it

Some Fords, and maybe others, use a variable displacement compressor to regulate pressures, flow and help fuel economy.

 

[Turbo74]

Mine did this exact same thing on a road trip. Only during that long trip and probably 5 or 6 times in 5hrs. I wondered what was going on lok

 

[ColonelAngus]

Pay attention as to if it correlates to your throttle. I had a weird issue like that (not a Bronco) and turned out to be a leaky vacuum line that operated the hvac doors. On throttle would lose to much vacuum and the door would open, off throttle there was enough vacuum to overcome the crack in the line.

With the Bronco its electric motors/servos/actuators, so it won't be a vac issue. Does the bronco in question have manual or acc?

 

[NotApplicable]

I think I’ve noticed the weird thing where the air surges to a higher speed randomly, like when taking some turns and whatnot. It didn’t necessarily concern me, but it has been noticeable…

 

[SamG]

Just received my bronco today, had a 6 Hour Dr., and it did the exact thing you were describing. No diagnosis but I thought I would just chip in. Seems to be a feature not a bug LOL

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