aghee

Hi everyone, So for starters I have searched and could not find any info on the problem I am having with my A/C and I am looking for advice or a solution if someone has had a similar problem. I have a 2008 GL450 with 70k miles. A/C has never required service. Yesterday, with the a/c set on 68 degrees, front zones synced and rear zone off, the a/c would work fine for about five minutes and then get hot like the heat was on for five minutes and then go back to being cold again. This happened several times over the course of a half hour drive. Went out again last night and had the same issue after first ten minutes of driving, so I lowered climate control temp to 64 degrees and the problem did not recur. Also, this is not a case of only one side being hot and other side remains cold. Both sides are blowing hot in my case when they should be cold. Anyone who has had a similar situation and resolved it or anyone with advice to diagnose would be appreciated. Thanks, John

aghee

I wanted to post an update on my issue as I can now provide more detail. If my climate control is set to AUTO, it will work fine and cool the car for about 25-30 minutes and then the air temp will just rise to hot and the fan speed will increase all on its own (I am not touching the temp control at all). The temp will then fluctuate from hot to cold, but only when in AUTO. If I switch the a/c to manual and just set the temp and fan speed manually, there is no issue and the a/c works fine. I have several guesses as to what this might be but am hoping that someone here can provide some additional insight. Any help would be appreciated.
Thanks,
John

joshd2012

That sounds like a thermostat issue with the climate control. I can't recall exactly where, but it is located near the climate controls and is pictured in your manual. Is it blocked? If not, that likely needs to be replaced.