The Honda Civic is among Honda’s best-selling hatchback and sedan cars.
It is consistently among the most popular and best-selling models in all major markets around the world.
Known for its good looks, sporty handling, and a great list of trim options, the Civic is firmly planted in hearts and minds as one of Honda’s great creations.
This article answers the question “Why Honda Civic Heater Only Works While Driving?”…
Why Honda Civic Heater Only Works While Driving?
There are several possible causes that can lead to your Honda Civic heater not working when you come to a stop. These reasons generally relate to engine coolant, heater control valve, vacuum hoses, and the thermostat. If any of these have a problem, it can cause this particular heating issue.
When you’re driving, heat will always be generated because the coolant will naturally get hotter and therefore the heater will have hot air being generated from the engine core.
If the problem lies with your engine coolant, then it’s either that your coolant level is too low.
If your coolant levels have dropped, then it indicates that you might have a leak somewhere in the system.
You shouldn’t lose coolant just like that.
Take the car for a professional to take a look at. The diagnosis and repair of a coolant leak shouldn’t cost more than $45-60 plus taxes and additional fees.
Once the leak is fixed, then a mechanic may have to flush the coolant replace it.
If you have the mechanic do this, it will likely cost around $80.
If all system components are in good order, however, flushing the coolant and replacing it with fresh pre-diluted coolant is a fairly simple task that you could attempt yourself to save money.
The best kind of coolant to use would be genuine Honda antifreeze since the formula in that coolant is designed to prevent corrosion and work especially well in the specific Honda engine design.
Genuine Honda antifreeze is about $26 for a gallon.
Alternative brands include Prestone, Zerex Asian Vehicle, and Valvoline. Prices for a gallon of these coolants are similar to that of the genuine Honda coolant.
Heater Control Valve
When your engine reaches its optimum operating temperature, the heater control valve is supposed to open up.
If it fails to do this, it can create the issue of no heat being generated when the car is idling.
If you have to have the heater control valve replaced, then this is likely to cost you between $131 and $149 including labor costs.
Both the heater control valve and the heater core are very tricky to work on, so we don’t recommend anyone attempting DIY jobs on these.
Problems with your heater control valve failing to open can be caused by leaks in the vacuum hoses that connect to it. Inspect these hoses and look for any signs of leakage.
You probably would be able to smell coolant under the hood if these hoses are leaking. It’s typically quite a sweet smell.
To replace the vacuum hoses (heater hoses) will cost you in the region of $120 to $148 including labor costs.
Should they turn out to be leaking, you’ll need to fix them even if these aren’t the only reason behind your heater not working properly.
Another cause of the problem can be a faulty thermostat.
If the thermostat fails to close, which it can do when the coolant temperature is too low, then what happens is the engine will take much longer to warm the coolant.
Even worse, the car’s computer will believe that the engine is consistently cold, which will prompt much greater fuel usage.
If you need to replace a thermostat in your Honda Civic, the estimated job costs are between $164 and $190.
Blown Head Gasket
If you have checked all of the above things and still the problem persists, then there is one more thing you can try: checking to see if you have a blown head gasket.
Some mechanics have found that after checking all the usual steps, the heater is still only blowing hot air when moving.
It’s quite frustrating, but there’s perhaps something they missed.
If they were to open up the radiator cap and take a closer look inside, they might find something quite unusual and alarming: exhaust fumes.
If you shine a light over the radiator you might see the fumes down in the radiator, but you can double-check by squeezing the upper radiator hose.
If there is exhaust in there, it will come out when you squeeze.
Upon seeing the smokey fumes come out of the radiator, there’s no reason to panic, but you should know that the most likely cause of your trouble is a blown head gasket.
Unfortunately, a new head gasket for a Honda Civic is an expensive job, with a total price for a replacement costing between $1,216 and $1,471. Nearly all of that is labor costs.
How To Correctly Diagnose The Problem?
The best way to diagnose this problem is to go through the above checks in the same order as we have presented them. These parts are largely interconnected.
The most likely culprit is the coolant levels and a possible coolant leak.
After that, you can check the heat controller valve, followed by the vacuum hoses that are connected to it.
Finally, if all the other factors look fine, you come to the thermostat, which by process of elimination should turn out to be where the problem is.
As you check through the list, you can eliminate possible causes until you reach the one you need.
As we mentioned, if you check all the way to the thermostat but find the problem still isn’t solved, then it could be a blown head gasket.
You’ll need the opinion of a good mechanic to be sure about that.
What Civic Years Are More Likely To Have This Problem?
It seems that the most affected model years for this kind of heater problem were 2006 to 2012.
That’s not to say that no other Civics could be affected by this problem, but these model years, in particular, emerged as a common issue.
The problem is most pronounced in all Civic models from 2006 to 2012, but if it happens in a later model then the causes of it are much the same.
Many Honda owners have complained about this issue even in vehicles from the 2015 model year onwards.
They complain that Honda has not reacted quickly enough to solve this known issue.
Mechanics seem to agree with them that’s it’s a real and common issue with the Honda Civic.
Is The Problem In Both Automatic And Manual Transmission Civics?
Yes, it is. This problem doesn’t seem to affect manual transmissions more than automatic transmission Civics.
The heater problems are not connected to the transmission, and so both styles of the drivetrain were liable to experience this kind of problem.
Do The Weather Conditions Trigger This Problem?
One way that weather can indeed trigger some of the conditions above is when it’s especially cold outside.
Cold weather can cause vehicle fluids to thicken, including antifreeze/coolant.
The thicker your fluids are, from engine oil to coolant and transmission fluid, the harder it is for it to move freely about where it needs to go.
If you then have the same heater problem while idling, then it becomes even harder for those fluids to warm up as they should unless you actually start moving at speed.