Car AC troubleshooting

[motomania2007]

I have an F150. Around town, the AC works great. On the freeway, it is noticeably less cold air.

What does that mean?

I presume that since it has good cold air at lower speeds that it is not a refrigerant recharging issue.

What should I check first?

 

[bruceflinch]

Guessing the clutch on the compressor is not engaging at certain RPMs.?

 

[Cycle61]

Maybe something letting in outside air to the system, more prominent at higher vehicle speeds?

 

[RS250 Chester]

A quick google search suggests to adjust AC gap, I assume at the clutch. It seems a common issue with the F150.

 

[westie]

My F150 AC cracked and the coolant would seep out in a couple days. It was a bitch to fix. Shop added colored coolant to find the crack. $$. And then whatever is was to replace. $$$. I sold it right after.

 

[augustiron]

May be a blend door issue. It is a motorized flapper by the heater core that opens and closes when heat/cold/vent is selected. If it isn't operating properly, hot air can come through when you have the ac on amd drive at speed.
Also, there may be foam seals around the Heather core enclosure from the firewall that went south (my e350 had that, and a bad blend door) again letting g in hot air from the engine compartment when moving.

 

[Cycle61]

May be a blend door issue. It is a motorized flapper by the heater core that opens and closes when heat/cold/vent is selected. If it isn't operating properly, hot air can come through when you have the ac on amd drive at speed.
Also, there may be foam seals around the Heather core enclosure from the firewall that went south (my e350 had that, and a bad blend door) again letting g in hot air from the engine compartment when moving.

Maybe something letting in outside air to the system, more prominent at higher vehicle speeds?

That's what I said, but with better words.

 

[motomania2007]

Thanks! I will check the account compressor clutch and the blend door. I thought maybe the clutch issue but didn't see how it could be. I didn't even think of the blend door...

 

[TheRobSJ]

Also check the water/heater valve. When your HVAC is set to cold, this valve (which is typically under the hood inline with one of the heater hoses) closes off any flow through the heater core. If for whatever reason this valve is not fully closing properly, then your heater core with have nice hot coolant flowing into it. A partially closed valve might not allow enough flow at idle to affect things, but when RPMs are higher (such as being on the freeway), the water pump flows more coolant and might flow who go through the heater core to keep it super hot.

Welp. That’s my guess since blend door was already taken.

 

[motomania2007]

Thanks! I will check the valve too.

 

[boney]

<--- just learned a few things, and what to look for in his 2001 grand cherokee.