2007 FJ Cruiser-AC Blows Hot Air AFTER Engine Coolant Service

Toyota FJ Cruiser Base Model 2 wheel drive
V6 (241Ci) 4.0L (1GR-FE), MFI
Mileage: 100,800

Hello All:

Can the engine coolant system/fluid directly or indirectly affect AC performance? Or, can an engine coolant system service affect (good or bad) AC performance?


3 weeks ago did some 100,000 mile maintenance on my FJ: Engine Coolant system service/fluid flush, Transmission Fluid Flush & replaced front/back shocks. After I got it back, my AC only blows cold air at night (60 degrees outside). And even at night after it’s been running a bit or on the freeway, it’s no where near as cold as it was before the service. During the day it’s worse (70 degrees outside). I can just barely feel cold air if I put my hand right next to vent & put the vents setting to blow only up top. Before the services I mentioned above, AC was blowing cold no matter how hot it was outside. It would even blow cold when idling, but blows very warm now when idling.

I didn’t notice this problem till about 2 weeks later. After I got it back, had a cold spell outside & wasn’t using the AC. But had a couple warm days in a row this week, used the AC, & then realized the issue. However, it was very warm in the days leading up to the service so I had used the AC right before I took it in. (Live in So Cal by beach & in winter it can be 80 deg one day & 65 the next).

When realized issue, called repair shop right away who did service. Was told the engine coolant service/fluid flush-replace has nothing directly or indirectly to do with the AC… that it was just a funny coincidence. So they want to charge me again ($152) to check AC/recharge it & add “freon” if it’s low. And more $$ if there’s a bigger issue (leak, etc).

My Question(s):

Is the repair shop being truthful that the AC problem is “purely coincidental” & has nothing to do with the engine coolant system and service they did?

He also told me the “freon” for the AC is a separate fluid than the coolant for the engine. Is that correct?

During the engine coolant service, could/should it have been discovered that the AC system had leaks?

If AC “freon” is leaking, would there be a puddle under the FJ after it sat for a while?

If I dont turn on AC, how long can I wait to get it fixed? I don’t have the money for repairs, so might be about a month before I can.

Things I’ve Tried:
Some experiments on the AC as described above (when it’s blowing all hot air, temp of day, changing vent settings, running the car on fwy, etc.) Nothing I try causes AC to blow at the cold temp like it did before service.

Last thing I’m going to try is changing the cabin air filter… it’s due. I haven’t tried that yet before posting because don’t have the funds to buy one right now (was also going to try to change it myself). But if it was the cabin filter, I logically would have had this problem before the service(s).

***below is the engine coolant service portion of the repair ticket @ service was completed:
FJC Engine Coolant Repair

Thank you all in advance!

FYI: I have no automotive repair experience - so am seeking advice on whether repair shop was truthful & then I can decide whether or not to take it back to them. I have only taken it in to them once before for spark plug replacement & had no problems.




They probably should have check the AC for functionality but would have to charge extra for checking for leaks.

No. Freon evaporates as it leaks

If it’s leaking and outside air gets in the system, it will contaminate components. If it is fully charged and the problem lies elsewhere it can wait. From my prospective the shop is OK.

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TC: Thanks so much for the reply & answering my questions. Sounds like the mechanic wasn’t a partner of Dewey, Cheetham & Howe!
I’m glad I found out I can’t wait too long to get it fixed, was going to wait till end of winter. I can at least get it recharged/checked for leaks/flushed & filled now (& their quote was very reasonable for all that) & if bigger problems are found, I can wait to fix those. Sounds like charging it will buy me some time. I guess she’s gettin’ old & have been very lucky that up till now.

If I were to check the level of AC antifreeze/coolant/water (I don’t know correct term) is it in a different container under the hood than the engine coolant? Since they are 2 separate things I’m assuming they are in separate bottles/containers? Maybe a good idea to check if my AC one is low.

Will check back in with update after getting it re-charged

I recommend that you find a friend or co-worker to show you some basic under-hood familiarity. Some fluids are easy to check, and at the age of your vehicle, you definitely want to know simple coolant and oil check routines.

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The A/C uses Freon (actually your system uses R134a, Freon is technically R12 an older refrigerant gas that was very nasty to the ozone layer when released into the atmosphere), which can only be checked by hooking up a gauge. This is something I would recommend you have taken care of by your mechanic.


Think of the refrigerator in your house it does the same thing in reverse from the AC in your car in that it keeps the cold inside in other words both need special equipment and know how to diagnose and fix trust your mechanic on this one this is not a problem to DIY.

Is the indicator light on the A/C button on steady or is it blinking?

Hello - Yeah I thought the freon was just a liquid that you can throw in & top off. I didn’t realize it existed in a gaseous state.

Nevada- The AC light is not blinking.

Today I let it idle for about 1 min with AC on max, trying to find the AC fan (couldn’t find it). But then after about 90 sec, pretty cold air was coming out of the middle and passenger side vents… but super warm on driver. WTH! I looked real quick online & bc I don’t have dual zone AC, it’s probably not the drivers side temp door actuator/servo motor. It’s still a low freon/needs recharging issue. Also my cabin air filter was very dirty. So yes I am taking it to mechanic, a professional needs to fix!

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There’s no direct connection b/t the engine’s cooling system, and the AC system, but both systems use the same engine compartment cooling fans. If those aren’t working the AC system won’t work either. The A/C doesn’t directly make the air cool; instead it moves heat from the passenger compartment to the engine compartment, where it is dissipated into the ambient air w/the engine compartment fans. If those fans aren’t working, the AC system won’t work either. Those fans are even more important, as they prevent the engine from overheating during long idles, like stuck in a traffic jam, waiting in line at Burger King, etc. Suggest to monitor the engine coolant temperature carefully until this problem is solved.