LMA1973

I just need some info in general on how the AC system works on the 1999 ML430.
I ask because mine is blowing hot air and i am beginning a diagnosis.
First, the two large fans at the front of the vehicle. Is one suppose to come on as soon as i turn on the AC because its not. If so, then there is the start of my problem.
I have checked fuse #44 and all is well there. Next stop will be checking the system itself for freon and pressure etc.

boardboy330

Good question...but you also drive an 11 year old vehicle...could just need recharging. Mine started doing the same thing this week...

Benzo 003

The fans at the front of the car are to cool the radiator coolant...they come on when the coolant reaches a predetermined temp. They have nothing to do with the A/C.

sosh

They also come on when the A/C is turned on.

boardboy330

My fans kicked on and off just now while the AC was on and I was recharging it. They would come on...stay for a little while...then cut off...over and over during the 20 minutes I was under the hood.

LMA1973

Thanks for the responses!! I have another question.

I think i found the low pressure port for the AC (passenger side firewall near battery). Where is the high pressure port? I found a recharging kit that checks the pressure of both the lo and hi side simultaneously, so i need to find the low port.

janitorc7

just had the same problem. Have a shop check your Air Conditioning controller. That would be literally the switches that you engage under your radio

LMA1973

I need to follow up. Took it to the shop-got an evac, leak chec k then recharge. AC and the two front electric fans now work perfectly.

sosh

Thats great, you did the right thing. Did they find a leak?? You will be cool this summer while the rest of the DIYers are sweating holding their cans of R134 from Autozone attempting to get theirs to work!!

boardboy330

Sosh has a hard on for me...so cute.

OP...glad what we suggested worked. Enjoy the cool air