Heater wont work

Tiny
TOMMYBOYD-
  • MEMBER
  • 1998 MERCURY SABLE
  • 3.0L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 180,000 MILES
Heater doesn't work, blows cold air
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Friday, November 20th, 2015 AT 12:07 PM

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Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check to see if hoses are hot when car is warm then if they are then see if both of the doors in pic are working or not those are for temp.both hoses should be hot when engine warm if not the heater may be plugged and you can try backflushing it otherwise it may be a vacuum leak or hose off.

This guide can help

https://www.2carpros.com/articles/car-heater-not-working

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Friday, November 20th, 2015 AT 1:10 PM
Tiny
CURTISINBOONE
  • MEMBER
  • 2 POSTS
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 155,000 MILES
Hi, I have 1998 Mercury Sable and the heat quit working. I got the heater core replaced and worked for a couple days, took it back and got the thermostat replaced and that worked for a while, so my dumb luck took to the same place again and they said the heater core was clogged again and needed flushed so they did that. They called me back said that didn't work must be something with the head gasket and that wasn't working any better. Well I went and picked it up and it's running far worse. Now it runs hot when I'm driving it and my coolent tank was bubbling when I shut the car off and smoke was coming out from under the hood, I'm guessing thats just from the overflow I hope. When I took it to them it was only running hot when in idle for like 20 min or so other wise would go to cold then back to normal and a little heat would come out when driving or have foot on gas when in park, now no heat comes out. Did they mess up my car by flushing it?
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
New heater core couple of days later got clogged up find this very interesting-did they check the heater control valve? Could also be airlock

Get it block and pressure tested
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
CURTISINBOONE
  • MEMBER
  • 2 POSTS
I should add some things, I didn't take my car back to get looked at till a couple of months after I got the heater core replaced but never really worked right almost right after I got it replaced, I waited because my wife's took a little while before started to work and get real hot. That's when they replaced the thermostat and didn't work a month later. Yesterday is when they flushed it and now works worse now then when I started and now $700 down the drain.
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
BRINKLEY
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 85,000 MILES
Heater stopped working. Blows out warm air after motor warms up, but then turns cold. No leaking, no dust discharge. Air conditioning works fine. Blower working fine. If it was the heater core, wouldn't it be leaking or blowing dust?
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
No, the heater core does not necessarily have to leak to be faulty. The radiator can be full and you could still have no heat due to faulty heater core. I would suggest removing and testing the thermostat though, it's much simpler to access and cheaper to purchase.
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
JOYCE V
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 192,000 MILES
1998 Mercury Sable - no heat. Temperature gauge goes up to about 1/3 (never to 1/2 which it always used to) and then floats slowly between 1/3 and 1/4. I have changed the thermostat, temperature control module & sensor. One mechanic said there was a screw in crooked in the heater case that was causing the blend door not to open and close properly. He supposedly put some kinda of plastic glue on the case and changed the blend door. I had some heat when I left his shop but later that day had none. He now will not return my phone calls after I paid him $350. If I switch from cold to hot, the air gets a little warmer and I can hear a pop like the door is switching over.

Another mechanic said the coolant fans are kicking on when they shouldn't be. Right after starting car if I turn heater to the vents and floor the coolant fan kicks on before the car warms up. He said they should only kick on when on defrost if on the heat side. It's very cold right now so we took the fuse out of the coolant fans so they wouldn't kick on but still no heat.

The heater hoses are hot coming from the heater core and the core was changed just two years ago.

I noticed the other day that my gas guage was also floating between 3/4 & 1/2. Could all of this be due to some electrical problem?

I sometimes smell antifreeze but there has been some spilled on the overflow tank. I don't have white smoke coming from the tail pipe. I had the oil changed and they said it looked okay. I was concerned about a head gasket problem. The second mechanic started the vehicle without the overflow cap on (my suggestion to check for bubbles) and it did push coolant out the top (I thought maybe this was because it had been filled completely to the top). This mechanic didn't act like it shouldn't so I'm not sure either way.

I've now spent $500 and still have no heat. Please help!
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Wednesday, November 13th, 2019 AT 5:20 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,005 POSTS
Based on your description, it sounds like the engine isn't getting hot enough to heat the vehicle. Try this. Start the engine, let it warm up with the heater on high. Feel both heater core hoses. Both should be hot. If they are, recheck the blend door. If only one is hot, flush the heater core.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
HARLEYMAN2
  • MEMBER
  • 2 POSTS
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 160,250 MILES
Have no heat, coolent is good, temp gauge is where it should be, turn knob to high and nothing, wasn't a big deal in the summer, the AC works fine, just no heat. I got some radiator flush, maybe a clogged heater core? Can you tell me how to get at the heater core?
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
CHECK HEATER CORE hoses by firewall both hoses should be hot if not heater core need to be flushed
best if isolate heater core and flush
if both hoses hot and no heat suspect blend door and or blend door actuator remove radio and check
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
TMONEY9887
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 78,000 MILES
Was recently driving with the heat on. And noticed only cold air will come out. The next time I started my car, I let it warm up for about 10 minutes, got in and turned the heat on. The heat worked for maybe 30 seconds. Then it got cold again. I was driving to work and also noticed that the temperature gauge was all over the place. Going up to almost the red line the going back down to halfway. Very quickly. Seems odd knowing it is likely impossible for it to go from hot to cold and hot again that fast. I dont know much about cars and ANY help would be so greatly appreciated. Thanks in advance
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Taurus and Sable flush.
Thank you for the donation, and good description of your situation, very refreshing. You have a heater core plugging up.

Remove the heater core hoses at the firewall. Be easy with it, you do not want to rupture the core taking the hoses off. You may want to just cut the hoses flush at the nipple of the heater core, remove the clamps and make a cut on the hose so you can peel the cutoff hose that is still there.

Get two pieces of 5/8" heater hoses that are about 10-12 inches long each. Slide them onto the heater core nipples, no need to clamp.

Take a garden hose and with moderate pressure spray the heater core in one direction and then into the other hose to start to get some of the loose sediment. IT will like really brown/red/orange kind of color. When water runs clean, pull off the lower hose and let it drain and reattach. Buy a bottle of coolant flush chemical and pour it into the higher hose. Both hoses should be pointing up. One 12 oz bottle should fill the core. Let it set 3 hours. Backflush the heater core like you just did and reattach the original hoses and clamps again only if the coolant is clean.

IF the antifreeze looks dirty that is in the reservoir, then you should connect the two heater hoses so they by pass the heater core and flush the system thoroughly.

Once the entire system was flushed properly, and then reattach the heater hose to the core and top off the system. Recheck the level next time the car has cooled to ambient temperature.

Take a garden hose and with moderate pressure spray the heater core in one direction and then into the other hose to start to get some of the loose sediment. IT will like really brown/red/orange kind of color. When water runs clean, pull off the lower hose and let it drain and reattach. Buy a bottle of coolant flush chemical and pour it into the higher hose. Both hoses should be pointing up. One 12 oz bottle should fill the core. Let it set 3 hours. Backflush the heater core like you just did and reattach the original hoses and clamps again only if the coolant is clean.

IF the antifreeze looks dirty that is in the reservior, then you should connect the two heater hoses so they by pass the heater core and flush the system thoughly.

Once the entire system was flushed properly, then reattach the heater hose to the core and top off the system. Recheck the level next time the car has cooled to ambient temperature.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
BRANDI FABIANO
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 120,000 MILES
What can I do to fix or find the problem? Please help, thank you, cold in alaska the car puts out moderate but not hot heat only when you are driving, the faster you drive the hotter the heat but no heat when idling or going slower (35mph). Does not over heat. Have flushed radiator and heater core and replaced thermostat
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
DRCRANKNWRENCH
  • MECHANIC
  • 3,380 POSTS
When the car is at idle it runs cooler because the number of combustion's compared to number while driving is significantly different. If you held the idle at 4000 RPM at idle it would get hot like you were driving. However the lack of a load on the motor would destroy it.

You would think the airflow from the car moving would cool it off but the flow is actually not as great from movement as you would think. This is because it is not good for fuel economy to let a lot of air flow made from the car moving into the engine bay or even under the car.

The fan is more than adequate and you might see that car makers have shy ed away from large open front grilles that are open and let air into the engine bay. It creates drag on the car as it gets trapped in the engine bay and creates a lot of drag. It used to be for performance to let cool air into intake but it has been found that the air drag far exceeds any Horsepower gains. With that said the fan is essentially the source of air for cooling the engine and there are a lot of hot explosions going on in the cylinders which make the temperature slightly higher. Even 5 degrees hotter than at idle will make the heater feel very different. Todays A/C systems are only required to make the car 20 degrees Fahrenheit cooler than outside and when it is 100F it can be hot in car.

Heaters are more efficient and the heater actually aids to cool the engine. A heater uses a part called a heater core that looks just like a small radiator which has coolant running through it which is recirculated by a valve. The valve opens more to allow more coolant flow and therefore the temperature of the heater is higher. So, one things to check is that the heater valve is opening all the way. It is located on the intake hose of the heater core near the firewall. There are two hoses that run to and from the engine and to the firewall near the center.

They are close together, one right on top of the other. You will see the valve on one of the lines at the firewall. Most are cable actuated. Check to make sure the cable is securely fastened to the bracket which holds it in place. It is actually clamping the cable case so that the inner cable can move without the outer cable sheath moving so the cable can move the valve arm as far as possible.

Sometimes they get loose and any movement will keep them from opening the valve all the way thus not allowing as much coolant as possible to run into the heater core. Also check that the valve is moving all the way. Turn the heat off and note the position of the valve arm and then turn the heat all the way up and it should be 90 degrees from the prior position which is full open.

You might want to see if you can get a higher temperature thermostat for the car. The stock thermostat starts to open at 193-200 Degrees Fahrenheit and is fully open at 224 Degrees Fahrenheit. Thermostats will have the fully open temperature stated when they are sold. So, you might try to find a special cold temperature thermostat that is fully open at 230 Degrees Fahrenheit.

Look around the internet and try to stick with a reputable company like STANT thermostats. One thing you will note that freight trucks do is to have a radiator blanket over the front that can be opened or closed more or less to adjust for temperature. This is generally not only for running on highway temperature, but they spend the night in their cabs sleeping with heat coming from the engine idling and the regular heater system supplying heat.

So they can make the radiator opening smaller to make it a little warmer for the heater. The cooling fan does not come on at the same temperature as the thermostat, it comes on when the temperature gets a little hotter. So, covering the radiator can help keep it warmer at idle yet not overheat the motor at driving or highway speed. Again aerodynamics is not a concern so airflow will be different from your car. If space allows, you might try a piece of cardboard to cover some for the radiator and let it idle to see if it warms it up some and then drive it to make sure it does not overheat.

If you don't have a temperature gauge, this is somewhat risky, but the overheat light on the dash will come on and you must immediately pull over and turn the car off and be able to remove the cardboard. If you try this the car actually gets hotter when the is turned off. So, it is possible the radiator cap might release pressure and hot steam will come at at high pressure. So wait a few minutes before you open hood to remove cardboard.

You might also try just replacing the thermostat and if you have not changed the ani-freeze in the last 2 years change it as well. In most temperatures the ratio of water to anti freeze is 50/50. But, you will see on anti-freeze containers that the manufacturer suggests a ratio with much more anti-freeze than water. This protects the motor to colder temperatures.

Anti-freeze doest cool off a motor as well as water and having new fluid may help as anti-freeze becomes more like water over time in its anti-freeze and heat dissipation qualities. The greater amount of anti-freeze will also help to warm it up some.
Another thing you can do which is probably the best option is to change the fam temperature switch. You can get higher temp switches or you can get adjustable relay fan switches all in one that will override the whole system.

They are available at most auto parts stores and are not hard to install. They have a sensor that can be pushed into the fins of the radiator, DO NOT DO THIS. Simply attached the sensor with calbe ties or other means near the upper radiator hose at the radiator. Pushing it into the fins can cause damage. You can just turn the turn on fan temperature the a lower setting to accommodate for not following the manufacturer direction. This is just my opinion not to shove the sensor in between the fins when the near same can be achieved via aforementioned. The realy will have an adjustable rheostat that you can play with as far as when the fans come on. You could sit with the car at idle and turn the fans on just after heater gets how. They are generally not a huge range of adjustment and are within most engine specifications as to not allow a motor to overheat. So, this may be the way to go.
I recommend changing the anti-freeze first and maybe even use a higher than recommended ratio of anti-freeze too heat up the system just a little which may be enough. A new thermostat can be replaced at this time since the coolant is out.
Sometimes car manufacturers use different temperature thermostats depending on where the car is going to be sold. So, you mgiht try asking a dealership in Canada what the thermostat temperature is. It could very well be hotter and since it is made by manufacturer designed for your car is always the best.

So, you don't necessarily have an issue. If you did the temperature of the coolant would drop rather drastically at idle being that it is so cold. If the car was purchased in more southerly state the thermostat may very well be cooler. Finally changin the anti freeze and raito will help and is safe to do. Antifreeze is actually very good at lubricating and I had a car tht I ran in the state of Maryland with pure anti-freeze and no water and it never overheated. So, it is required for maintenance and has low risk factor.

I also had an Altima in Maryland tht would do the same thing your car is doing in temperatures above what your car sees. So I don't think you have an issue. You may have a slow to close thermostat that when replaced may help and the other items I mentioned. Use the cardboard over the radiator as a last resort as it is risky to an extent. You only need a few degrees to get the heater to feel warmer. Doing the maintenance checks and services may add up to what you need and are necessary anyway.
Good luck and I hope this information helps you to get a little warmer.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
THEDEEP
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 135,000 MILES
Heating problems when idling heater blows out warm air with normal temp but when driven temp dropes nad heater blow out cold air vehicle is a 1998 mercury sable
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
DRCRANKNWRENCH
  • MECHANIC
  • 3,380 POSTS
I would start with a thermostat and service to the anti-freeze if it has not been flushed and filled within the last 2 years or 30,000 miles.

Let me know how that goes or if you have any other questions.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
MARTIO
  • MEMBER
  • 3 POSTS
  • 1998 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 76,000 MILES
1998 Mercury Sable, Heater Blows Cold Air. Why?
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
If both heater hoses comming from the heater core are hot, the blend door is NOT moving, if the inlet hose is hot but outlet is cold, the heater core needs flushing, or replacement. If both hoses are cold, check antifreeze level and thermostat, also rarley but known to happen is the impeller blades on the water pump disolve over time and may not be pumping enough.
Heater cores on these are famous for clogging, go to a radiator shop and have is blown out.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
HARDCOVER
  • MEMBER
  • 1 POST
  • 1998 MERCURY SABLE
  • 200,000 MILES
Ive replaced thermostat. Heater doesn't work and car still overheats even with heat/air conditioning turned off.
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
When its hot is bth hoses to your heater core and radiator getting really hot?
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Wednesday, November 13th, 2019 AT 5:21 PM (Merged)

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