2010 GS350. AC air didn't seem quite so cold this year. Freon was pretty much at correct level. Mechanic friend noticed both of the 2 cooling fans were operating at very low speeds....if at all. Inserted some "test" style relays that basically can bypass the fan control module and turn fans on to high speed. Without fans running at steady speed the AC compressor will not stay engaged continously.

So, we are thinking that the AC fan control module is finished (it was very warm when we took it off). Thinking to order new module from RockAuto @ approx $155.

Any opinions on our thoughts? Please feel free to offer thoughts/opinions/advicef anyone thinks we are way off base or has recommendations.

Thanks for any thoughts.

 

When was the last time you replaced your cabin filter? If it was awhile, go ahead and replace it. Mine was clogged, and when I installed a denso brand it was like night and day for my ac. The air blew stronger out of the vents so it cooled the car a lot quicker.

Next I would inspect the condensor and the radiator fins. Both maybe clogged with dirt and debri, you can easily put a high pressure water hose directly on both and flush out the clogged fins. If you can remove the top mounts of the radiator im pretty sure you will find a layer of caked up debri like what I found when I removed my radiator.

I wouldnt replace the fan relay, as im pretty sure the fan speed is regulated depending on how hot your car gets. Full blast on the fans only gets kicked on if your car really over heats.

 

Thanks for the reply. I will try to offer more info, best I can (I'm not a mechanic).

I have not replaced the cabin air filter in a long time.....if ever. It does look a little dirty so I will replace very soon. Although, I don't think this is really the issue as I can see that this might slightly restict some air flow into the cabin or maybe cause a bad odor but I doubt that it would be enough restriction to prevent cooling fans from operating to draw air across condensing unit.

The scenario:

It was an 85 degree day when I drove it over to mechanics house and we then left the engine run for quite some time, AC on full blast, fan speed switch on MAX. Both fans operated intermittently and only for a few seconds at a time.

We are thinking the compressor is not engaging due to the fans not operating correctly.....in other words the output signal from fan module is not making it to the fan relays..or at least intermittently. We think this due to the fact that while the car is idling and hot and A/C on full blast, both fans operate for just a short time and cycle on/off.

When the fan control module was bypassed (applied power with his testing tool/probe directly to the wire that was leaving the module and going to the fan/relay), both fans would operate at a higher speed and the A/C compressor would engage. But, the fans would then stop abruptly in just a couple of seconds due to the fuse/circuit-breaker in his test probe popping...thus stopping the signal from continuing on to the fan relays.

So, we are thinking that this control signal coming from the module to the fan relays is not working properly.

Btw, the freon was almost at it's correct level (checked with gauges).

This all started due to it seemed like the A/C wasn't blowing as cold as it has past summers. I wish I could remember if I ever heard the compressor cycling on/off (this year) or not during normal driving. The only thng I ever really hear is the injectors or whatever that makes the loud "tick" that sounds like lifters.

Any thoughts? Anybody?

Thanks again.

So, now there is absoutely no cold air blowing out at all and the compressor is not engaging at all. That's why we are going down this path of the A/C fan control module being defective. Problem is...I don't really see anyone posting any issues of fan control module problems.

 

Forgot to mention that we did quick check of the radiator and condensor "fins" by shining flashlight thru and there didnt appear to be any blockage to note. I think I'll try using a sprayer through them to help make sure.

 

Try spraying the radiator and condenser from front/back and replace the cabin filter with a denso or oem. Its cheap good maintenance, if it works great if it doesnt atleast you will have clean air coming inside.

 

I replaced the cabin filter. Today I will try spraying the radiator and condensor fins with a hose to hopefully remove any excess debris..

I will be dropping it off later this week at a local auto repair shop that has a great reputation for troubleshooting cars. $85/hr. but I guess that's where I am at with this situation.

I'll post any results, in case it helps someone else out with a similar issue.

ibidu1, thanks for the feedback. Anyone else....please feel free to chime in. Thanks.

 

Sorry I must have missed your last post of where the compressor is not engaging.

When you and your mechanic friend checked the ac freon level is that the time the compressor stopped working? Im thinking maybe when you guys checked the freon level, some freon escaped and now not triggering the compressor. Because if the freon is slightly low the compressor will not trigger on.

Try this start the car and shine a light on the compressor clutch, it should cycle on and off. If it does not, you can try buying a can of freon with a gauge from an autoparts store. Start the car, install the freon attachment to the high side port. Read the gauge, If the gauge on the can is low add freon, wait for the compressor to click on.

If the freon is at the correct level and the compressor still hasnt clicked on, then there should be a plug on the compressor. You can use a test light to see if theres power coming to it, if theres power coming to it, then maybe your compressor clutch is bad. If theres no power then the next I would check the high pressure sensor. This sensor reads when high enough pressure and sends power to the compressor. That can be bad, but all these things rarely go out on our cars.

I'm betting your just low on freon!

 

So, back to my friend mechanic house to use his power washer to spray out coils. After chatting for a while, we decided to throw the guages back on to just have a look. The low pressure side was pegging (max.) but we were expecting it to be 35-45 ( apparently this can vary due to the ambient temperature and since it was 85 to 90 degrees out this evening we were looking for somewhere around 35-45 PSI on the low pressure side.

We decided to discharge a little of the freon. As the low pressure gauge started moving downward, we noticed that the compressor and fans were staying ON longer. We continued discharging until we got just below 45 psi and now both fans were were running on high speed, compressor staying engaged, and interior was blowing cool air. Continued this way for a good 30 minutes until I got home.

I guess we had too much freon in but that is puzzling to us as originally we had only added a tiny amount of freon (or so we thought?). Apparently, the AC compressor doesn't work if there is either too little or too much of Freon in the system? Makes sense but we are still baffeled as to how we added too much freon.

Im thinking to go ahead and take it in for the diagnostic tests and let them really "dial in" rhe proper amount of freon and also maybe they can give some insight as to why the smoke on startup (see other recent post in this forum).

ibidu1, looks like you were right that it was a freon issue. Thanks for all your input!

 

Your lucky your added freon didnt ruin your ac compressor, well glad you got it sorted out.

 

Yes, I agree.....at least not yet, anyway.
The past two days I've drove it home from work about a 40-minute drive 80 to 90 degrees each day in the AC was working great.

Ibidu1....thanks for all your input....for my threads and all the others!

 

I could find 12 volts by back probing my fans but they were not turning very fast? I had to use the - post on the battery for ground,Yep the fan was done for .I bought a new assembly off the eBay, i had to remove some of the plastic from the edges to make it fit on the radiator correctly but wasn't anything to hard.
DO get some weatherstrip foam 1/4 to seal the assembly to the radiator.
I got the assembly for 130.00 2 new fans a new relay switch and a new water overfill bottle,I shot my warranty because it's the wife's car and it was hot,so send in your VIN if you order one. I just checked my model, and after a phone call i got the news about the VIN, and maybe your luck will be better than mine. I did notice the condenser was getting too hot,you can put a GOOD fan in front of the radiator if that fixes the ac,you got it,As was mentioned check the air flow in the cabin, I have read the carbon coated ones are not good to use. I like the white ones.Recheck your Freon it will purge it out and some oil if your system gets too hot usually at the compressor pulley.
Turn your steering wheel all the way to the left and look inside the passenger wheel well you can see if it leaked any oil,if so it needs to be put back.
You can tap on the fan relay to check it ,if it's bad it will then run,there is a relay inside it.It is potted so can't fix it. Have fun I do !

 

Looks like all is well. Somehow, the system was overcharged with Freon. As we removed freon, the fan started to stay engaged longer and longer. Ww finally had it set to the correct freon amount (we think) and everything seems to be working well....so far anyway...and that's been a month or two now.

Thanks for everyone's input regarding this situation.