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Trouble with heat in my car, doesn't kick on at idle

24K views 8 replies 8 participants last post by  Steve@Tasca 
#1 ·
First off the car is 2006 ST. I bought it used a few months ago, and it has 40k on it.

As many of you know it is cold up here in the northern states.
So I noticed this a few weeks ago but it didn't start to bother me until lately when the mornings have been below freezing.

I'll warm my car up in the morning. When I get in to go, the engine will be up to temp. but there is not heat coming from the vents/defroster. It will take a long time before heat eventually starts to come out. However it does not produce any heat while the car is at idle or under 2000 rpms.

Is this a thermostat issue, or some kind of sensor?

When I'm driving on the freeway it doesn't bother me cause it's nice and warm, but a lot of my driving is stop and go and the car never warms up much.

Help me out, I'm cold!!!

Thanks
 
#2 ·
Does the blower motor in the car work? Meaning, if you start the car and turn on the fan, do you hear the fan blowing?

If not, then either the blower motor is bad or the resistor is bad. The blower motor and the resistor are both located inside the car, passenger side, under the dash.

The blower motor bolts in from the bottom of the heater/air-conditioning box (it's black). There should be a panel that would be covering the box under the dash. You would have to remove it to access either the blower motor or resistor.

The resistor is located (as my memory fails) to the left of where the blower motor bolts into the box.

What it sounds like is that the blower motor doesn't work and that when you get moving on the highway, the air is naturally forced into the box and pushes some of the hot air into the passenger compartment and thus you don't freeze to death while driving the car. Not a fun experience, as you already have experienced.

I say to check both or have someone check it for you. It's also possible that you have a blown fuse and or a bad fan control switch.

The easiest thing to do is to remove the blower motor and bench test it. The resistor should be tested via an ohm meter. A fuse is a no brainer, but warrants the question "why did it blow". If the fuse is blown, replace it with one of the same amperage -- NEVER replace a fuse with one that is of a higher amperage. If it's the fan control switch on the dash, you would test it via an ohm meter. Also, and hopefully, it's not a broken wire. Tracing down broken wires/terminals sucks.

Hope this helps and good luck!
 
#3 ·
No, no, the blower motor works perfectly fine. It justs blows cold air out when the car is at idle. When the car is driving 1500+rpms the heat works, but not till I've been driving for like 10-15 minutes.

Last night I was waiting at a friends house with the car idling and the heat wasn't on, and I noticed some steam coming from under the hood. I shut the car off and could hear bubbling coming from the engine bay, specifically the coolant overflow box.

Does this help any?
 
#4 ·
So I came on here to post about this exact same problem that my car (00 zts) just started experiencing. I was going to post in the team tech thread but I'll see if I can get any posts here.

Blows cold air at idle. When I'm driving it is nice and warm, but when I come to a stop at a stop light, it's warm for about 15-20 seconds but then it starts blowing cold air. It is still blowing air through the vents, but it is as cold as the outside air. Once I start driving again it warms right back up.

Ideas?
 
#5 ·
umm, check your coolant. i had a prob with my truck, same symptoms, it was low on coolant. if that ain't it it sounds like a thermostat isn't working properly. cheap to fix
 
#6 ·
i have the same problem with a 93 mercury cougar xr-7 we just replaced the water pump and themostat and filled the coolant yes the blower works so what else could it be? it read hot and kicks on for a few seconds then blows cold again. plus my car also does when it comes to a complete stop and i go to go again and it wont start until i hit the gas but then it runs fine after a few.
 
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