Truck AC question

My 2007 F150 AC worked fine until the TX temps went full hell. I hooked up gauges and the high/lo pressures are spot on. Vent temps stay around 60 in around town driving at 100 ambient. I've researched a bit and found some info on people adding a pusher fan to the front of the condenser to assist in cooling. My truck would be an easy install for 1 or 2 fans - there's easy access and plenty of room.

Have any of you ever tried this? What were results? thx

[Scott R]

Simple things to check too, is the pollen filter clean?

[asphaltgambler]

If you checked your pressures and they are fine, the issue is with your blend / climate control system.

Originally Posted by Scott R

Simple things to check too, is the pollen filter clean?

Don't know but there is plenty of supply from the vents

Originally Posted by asphaltgambler

If you checked your pressures and they are fine, the issue is with your blend / climate control system.

Maybe so. I bought it a couple months ago so don't know how the heater performs.

[cabmandone]

Is the condenser clean? When I had to replace one due to a leak I was amazed how much crud had built up in the condenser. Also, in high temps try running it in either max or recirc mode.

[mattdavis11]

Glen put an electric fan on his El Camino. He tied into the brake switch or something, and put a delay in line so it would only turn on when on the brakes for an extended period of time. Problem solved, IIRC. Stop lights and traffic kill a/c systems on vehicles with mechanical fan clutches.

That said, I would like to know what the pressures are. R134a pressures fluctuate, and do so quite a bit when it's this hot. It's 109 outside right now in Austin. My home unit is struggling.

[asphaltgambler]

What are the low / high side pressures?

Originally Posted by asphaltgambler

What are the low / high side pressures?

275/42 @ 90 degrees

Condenser is clean.

Thx

[mfiazzo]

Hi Mark, the low pressure should be around 30 psi at 90 degrees.

Did you purge the line before you installed it? Sounds like you may have some air in the system. Can you find a sight glass near the condenser? If you can, turn on the A/C and look at the sight glass, it should be running clear. If you see bubbles, could be low on freon or air in system.

Originally Posted by mfiazzo

Hi Mark, the low pressure should be around 30 psi at 90 degrees.

Did you purge the line before you installed it? Sounds like you may have some air in the system. Can you find a sight glass near the condenser? If you can, turn on the A/C and look at the sight glass, it should be running clear. If you see bubbles, could be low on freon or air in system.

Interesting - the website I looked at showed the low side at 45 or so. Maybe it was wrong. I did purge it - I'll have to look for a site glass. thx

[mfiazzo]

keep me posted

[onewhippedpuppy]

When I'm fighting weird A/C issues I find that it's easier to simply vacuum down the system and recharge per the manufacturer spec. That way you know it has the exact correct charge and minimizes the variables associated with an older car. You can get a decent vacuum pump at Harbor Freight for $60 and R134a refrigerant is cheap.

Otherwise check the usual stuff - clean condenser, clean evaporator (several products to foam clean the heater box), check fan clutch, make sure the compressor clutch is staying engaged, check the sight glass for bubbles if equipped.

[GH85Carrera]

Originally Posted by mattdavis11

Glen put an electric fan on his El Camino. He tied into the brake switch or something, and put a delay in line so it would only turn on when on the brakes for an extended period of time. Problem solved, IIRC. Stop lights and traffic kill a/c systems on vehicles with mechanical fan clutches.

That said, I would like to know what the pressures are. R134a pressures fluctuate, and do so quite a bit when it's this hot. It's 109 outside right now in Austin. My home unit is struggling.

Yep. It helps a LOT. I put an electric fan that only comes on when the compressor is running, and the brake pedal is pressed. It has a 5 second delay so if I have to tap the brakes a little the fan does not spool up.

Before the fan, at a long traffic light (like most of them) the AC temp went up fast. Now with that fan, it can keep blowing cold for a few minutes. I pretty much forget it is there except when I pull into my garage and shut down the car. I can hear it spooling down.

At first I had it only run if the compressor was on. The fan was noisy while driving down the highway and totally unnecessary. It is a great help.

[cabmandone]

Overcharging can cause the vent temps to be too warm. I use a digital scale and weigh the refrigerant into the system after putting the system in a vacuum. Look at your suction line while the A/C is running. Is there condensation on the suction line? If yes, you're close, if no you could be over or under charged which just requires a bit of add or subtract to figure out. Also look to see if you're getting condensation out of the drain. I have always been pretty close on charge when I get condensation forming on the suction line. I usually check vent temps while charging. If you see vent temps drop and then notice as you're adding the vent temp is rising it's a good indicator you're overcharged.

[asphaltgambler]

Make sure you check the pressures at slightly above idle - @900 / 1000 rpm for accurate reading. Your pressures are too high indicating overcharge situation. If you don't have access to a A/C recycling machine, you could bleed the low side while it's running being careful to only bleed the gas, not enough to let liquid out - so to get the pressures back down.

[1990C4S]

Isn't a 40 degree differential about normal?

I would switch to recirc and drop the inlet temperature until the car cools off.

Maybe the problem is it's 100 degrees where you live....

OK - I punted and took Matt's advice. Took it to my local shop and was diagnosed as a bad expansion valve and orifice tube. Should be chillin tomorrow... Thanks for the help

[T77911S]

Originally Posted by asphaltgambler

If you checked your pressures and they are fine, the issue is with your blend / climate control system.

right here^^^^

[mattdavis11]

I suspect they have found debris (metal slivers) on the orifice tube (no expansion valve on his truck) indicating internal compressor damage. While it is still pumping (high), it won't bring down the suction side (low) like it did before. Most shops don't know that in order to bring down the high side, you have to bring down the low side.

This heat will do a compressor in. What you might want to consider, is having the shop install a variable orifice tube to combat pressure increases caused by high ambient temperatures. They can be nearly as effective as an electric condenser fan. Then again, most shops don't know what a variable orifice tube is.

The part number for the variable (adjusting) orifice tube for your truck is EX 7000C (universal air cond). Any local parts store should be able to cross ref it and get for you. If not, I can send you one. If you need a new system, also, let me know. It wouldn't be difficult to get one for you quick, for whole lot less.