throwing a part at the sonata.

[JustinH]

Hey Guys,

Have this 2011 Sonata, here is the deal.

The AC works most of the time, but sometimes it will blow warm for an entire trip. Then I start it up and it works fine the next trip.

Took my wife to the movies last night, it was about 99 degrees outside and it was warm the entire 20 minute trip.

I thought it may be condenser fan, but this model appears to have one fan ,and its coming on fine. Car not overheating.

Before that it has been working fine, except one friday coming home from work it didn't run most of the trip (30 minutes, mostly highway).

I'm an IT guy not a mechanic, and I have done ok just throwing parts at this car before.

I purchased an OEM evaporator temp switch sensor for about $20 on ebay, should be here by Tuesday.

It seems to be easily replaced in the passenger footboard.

I also cleaned the front of the condensor with simple green and water, it was not too bad to start with, so I don't think that is the problem.

Put my hand on the high and low side, one is hot one is cold.

Cabin filter is new and clean.

Any other thoughts?

Thanks,

JH

 

[mk378]

If the low side is consistently cold, the refrigeration system is working and the evaporator is making cold air. Likely there is a blend door issue so the heater core is fighting the A/C.

 

[Kira]

same

 

[JustinH]

I was thinking blend door also, but this does not seem to be a common failure with the sonata. The common failure for warm/cold/warm/cold is this sensor.

I don't have a manifold set, we just moved into a new house and all my tools are in Austin in storage, so I barely have a screwdriver.

 

[Jethro_Bob]

I had a similar issue with my s10, try swapping the ac relay with the horn relay, if the issue disappears for good, replace the weak relay.

 

[thescreensavers]

Originally Posted by JustinH
I was thinking blend door also, but this does not seem to be a common failure with the sonata. The common failure for warm/cold/warm/cold is this sensor.

I don't have a manifold set, we just moved into a new house and all my tools are in Austin in storage, so I barely have a screwdriver.


FYI, Oreillys rents out the manifold set.

Check the pressures when its not blowing cold. If the pressures are good then you know its likely a blend door issue.

Also if you can find a service manual for your car that would help alot, as it usually lists the troubleshooting steps the dealer would do.

 

[mk378]

Like any intermittent problem, you do have to wait until it is not working then check. But it is real simple to pull over leaving the engine and A/C on and open the hood to feel the suction line. Don't bother feeling the high side line it is always going to be hot, often enough to burn you.

Also while you are in there observe if the compressor is engaged (front plate on the pulley is spinning) and if the condenser fan is running.

 

[eljefino]

This is apparently also an issue with ford fusions. Dumb that a temp sensor is the most fragile part of this system.

 

[HemiBenny]

A problem that we have found in some Hyundai's that cause either intermittent cool air or just flat out warm air is a failing exspansion valve. On your Sonata, it's located right on the firewall, just follow the lines right to it.

 

[Nick1994]

Originally Posted by Jethro_Bob
I had a similar issue with my s10, try swapping the ac relay with the horn relay, if the issue disappears for good, replace the weak relay.

+1

 

[Oro_O]

Originally Posted by Nick1994
Originally Posted by Jethro_Bob
I had a similar issue with my s10, try swapping the ac relay with the horn relay, if the issue disappears for good, replace the weak relay.

+1


+2 - Slightly older Lexuses had this problem and this was the way to diagnose it. An updated relay was eventually spec'd for them.

 

[JustinH]

Just a follow up to this thread. I found a guy on yelp with a local shop/used car dealer.

Real nice guy had a snap-on ac machine. Put dye in the system and the low side port valve was leaking. Pulled out all the refrigerant out of the system, the machine cleaned it, and added the exact amount with the correct oil.

He replaced both schraeder valves for me as well, $120 cash.

Very fair deal ac is cold again, good because it was 102 degrees all week.

Sat and talked to the guy, he explained that refilling from cans is a good way to get air in the system, and its hard to get the right charge unless you have a machine.

 

[JTK]

Was the system low on refrigerant?