2010 Hyundai Sante Fe - erratic engine rpms when A/C on?


  #1  
Old 03-22-15, 06:44 AM
J
Member
Thread Starter
Join Date: Oct 2014
Location: US of A
Posts: 62
Received 0 Votes on 0 Posts
2010 Hyundai Sante Fe - erratic engine rpms when A/C on?

Hi Everyone. Having some strange stuff go on with my wife's car. Here's the details:

Year: 2010
Car: Hyundai Sante Fe
Mileage: ~61.5k

Symptoms:
  • While driving down the highway with the A/C on, I notice what felt like a loss of power - not entirely - but almost like a hickup. Almost as if someone had lightly tapped the brakes.
  • Made it home, and tested the car in park. Took the RPM's up to 3000. Every so often you would here a strange sound and the RPMs would drop to about 2500 and then rebound to 3k.
  • Turned the A/C off, and the sound & RPM drop goes away. Turned the A/C on and the sound and RPM drop came back. Tested this multiple times so I'm pretty confident it has something to do with A/C
  • The car had the A/C head unit replaced on it before.
  • Tested all the normal items - checked the oil, cleaned the air filter, etc - all were normal. I also have a code reader, and there were no trouble codes being thrown by th CPU.

Of course...since we aren't the original owners of the car, Hyundai saw it fit to screw us over and drop their 10y/100k mile warranty to 5yr/60k miles -which incidentally - the car of COURSE just elapsed.

While under warranty however, the dealer went in and replaced the AC 'head' unit as the fans and controls seemed to act erratically. At that time the A/C head unit was replaced and the dealer told us we were lucky because it is a $4k repair.

I'm PRAYING it's just a busted head unit again, because that 'should' be fixed cost free by the dealership (since it was done within the last year or so and 10k miles). Could it be something else? What is the basic function of the head unit? Does the head unit have the A/C compressor on it, and could that compressor locking up be causing the erratic engine RPMs? I plan on taking it to the dealer, but want to be prepared.

Thanks for any help guys. I'm just really worried I'm going to get stuck with a ridiculous repair bill which will inevitably screw up our search for a new home. We just had kiddo #2, and our house is bursting at the seams, so I'm hoping this repair will either be covered or a simple fix
 
  #2  
Old 03-22-15, 11:32 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,166
Received 1,525 Votes on 1,408 Posts
While under warranty however, the dealer went in and replaced the AC 'head' unit as the fans and controls seemed to act erratically.
That sounds like the dealer changed the climate control computer or controller since it affected the fans. That is not a $4K job.

Maybe you aren't describing the repair correctly. Do you know exactly what was replaced ?

There is a head on the A/C compressor but it's not normally replaced. They would just change out the entire compressor. It is normal to feel the A/C compressor come on when driving or sitting still but what you are describing sounds a little more pronounced.

It could possibly be a failing A/C compressor.
 
  #3  
Old 03-22-15, 01:33 PM
ukrbyk's Avatar
Member
Join Date: Mar 2010
Location: USA/ Pacific NW
Posts: 3,652
Received 16 Votes on 13 Posts
My 1st suspicion will be over charged AC resulting in extra whoomp required from compressor to spin it.
Lik PJ, I have no idea what is "AC head unit". Never heard of it. AC is rather a very simple system, you know. Radiator, compressor, heat exchange radiator, lines, handful more parts. Head unit??
Anyhow. AC comp does take quite some power away from engine. ECU compensates with higher RPMs every time AC comp engages.
Prayer be heard, but if everything on AC side is OK, then it's your engine losing its power, resulting on rather abrup response to AC effort, compensated by ECU.
 
  #4  
Old 03-23-15, 08:48 AM
J
Member
Thread Starter
Join Date: Oct 2014
Location: US of A
Posts: 62
Received 0 Votes on 0 Posts
Hi Guys,

I got more information on what the dealer fixed the last time with regards to the AC unit.

The guy at the dealership said they fixed the "Control Head" for the AC. I'm researching what the control head does right now, but I'm assuming that's referring to the AC's computer rather than the car's computer?
 
  #5  
Old 03-23-15, 09:42 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,166
Received 1,525 Votes on 1,408 Posts
The control head for the A/C is the climate control system inside the car. Typically the actual control head would be the part in the dash where you controlled temps. That would connect to some type of control box that would control things.

The problem you're having now isn't related to that.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: