Heater intermittently not working

MEGMAP

MEMBER
2008 MERCURY MILAN
4 CYL
2WD
AUTOMATIC
70,000 MILES

When I start my car, the display for my heating/cooling 2ill light up, go dark, light up, etc. If I try to turn it on before driving, it won't work. Sometimes it will intermittently blow ice cold air for 10 seconds then shut off and repeat this pattern. I can push and hold the "off" button and sometimes this will help. Usually, after about 10 minutes of driving, I can turn the heat on. Although sometimes, it will still kick off again. I am clueless as to the source of this issue. Any ideas? Thanks!

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,269 POSTS

Hi,

If the light is going on and off, it sounds like it could be a power supply to the control module. Let's start by checking a couple of simple things.

There are a few fuses that may not have a good connection that provides power to the circuit. Also, there is a blower motor relay that can be going bad.

First, locate the relay in the battery junction box. If there is another relay with the same part number, switch them to see if there is any change. While there, also confirm fuse 4 is tight and not corroded. See pic 3 for locations.

If there isn't a relay with the same part number, here is a link explaining how to test one:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Next, I need you to check fuses in the vehicle. Under the dash is the smart junction box. Locate it and check the conditions of fuses 13, 23, and 27. See pic 4.

Let me know what you find.

Take care,

Joe

See pics below.

Images (Click to make bigger)