Honda Pilot 2019 Overheating. AC stops working

Hello. My wife has a 2019 Honda Pilot with 88,903 miles. Three months ago, she told me that the AC suddenly stopped blowing cold air, so she turned it off until she got to our house. I drove the car for a while and it blew cold air at all times. This problem disappeared until today.

Today my wife was driving the car and while she was waiting at the traffic light, the AC stopped blowing cold air and she received an alert about the engine temperature; the gauge was at maximum, but she saw no smoke.

I arrived at the place. I checked the Coolant level in the container and it was at the maximum. I looked under the vehicle and didn’t see any leaks. The serpentine belt was not broken. I started the vehicle, the AC turned on and both radiator fans came on. It took me 30 minutes to get to the place and the temperature gauge was half way down (normal).

My wife drove the vehicle to our house (5 miles) and the car did not overheat.

At this point I don’t know if it is a faulty temperature sensor, thermostat or water pump. Any other idea?

Thanks in advance.

Did you actually check the level in the radiator itself?
Once it cools down completely, I strongly suggest that you remove the radiator cap and take a look.


It is likely the car thinks it is overheating and turning off the AC to relieve the stress making it hot.

Taking the temperature of the car when it is at the normal range and again when the needle approaches hot and comparing will tell you if the car is actually getting hot or not. If not, plug in a diagnostic scanner and read the temperature from the OBD2 port. If it shows hot and the car is not hot, the sensor is a pretty good bet. If it confirms it is hot, then look elsewhere.

I’d check for a blown head gasket. Warm the car up from cold with the overflow bottle cap off. As it warms, do you see bubbles? Or get a test strip kit to test for combustion products in the coolant. Bubbles and a positive reading is confirmation of a blown head gasket or cracked block or head.


My gm did same thing. Ac shutoff and message said motor hot. You will almost certainly have codes. Turns out thermostat was stuck open. I had a code for cold motor and hot motor. I think gm likes to prod you to get service by keeping ac off. Most folks like ac.

Hi guys. Thanks for your reply’s.

So I let the car in the garage till cold. I checked the coolant level from the radiator cap and it was full. Then I turned on the car, and let it run till it got to its normal temperature. I connected my OBD2 diagnostic tool and a thermometer on one of the AC vents.

I turned on the AC. Ambient temperature was 98F / 36C. The compressor started, and a few seconds later it turned off. Vent temp was 88F / 31C. After a minute the compressor started again and shut down after 5 seconds. It continues like that on a loop…

As soon as the car reached the normal temp, the compressor turned on and stayed on. Vent temp drop to 57F / 14C. I also removed the overflow bottle cap and there were no bubbles.

My OBD2 Tool doesn’t show the engine temp (or maybe I didn’t found it in the settings). The only Temps available are CATEMP11 and CATEMP21 which both were 842F / 450C and after a 5 minutes ride went up to 1,112F / 600C, but the Temp gauge stayed at the normal temp rate (at the middle).

Another thing I noticed is that when the compressor kicks in while the car is in idle at normal temp, sometimes one fan turns on for a few secs, and sometimes both fans turns on. But I thing this is a normal thing.

*I want to clarify that there’s no check engine lights ON.

98f in January? Nice.
I replaced my $40 scan tool that was 10 yrs old with a $50 tool that has coolant temp. Old one was flaky, it read codes but would not erase them.

Puerto Rico

My guess, nothing wrong w/the AC. Focus on finding what’s causing the engine overheating symptom. Your OBD2 scan tool probably will display the coolant temperature. You may have to read its owners manual to figure out how. Search for the acronym CTS, meaning “coolant temperature sensor”. Hopefully the engine isn’t actually overheating, the computer just thinks it is. If you decide it is actually overheating, and the engine compartment fans seems to be working properly, the first test is usually a coolant system pressure test.

My 195 thermostat keeps motor at 187-190. Must have weak spring. Vent temps are warm/hotish

Search again for coolant temp on your OBD2 tool. That is one of the mandatory values.

If the AC is on, most cars run one fan every time the compressor is turning. It makes the AC work better to draw air over the condensor.

1 Like

As far as the A/C not working properly you can have a leak.

A/C Does Not Blow Cold Air and Condenser Leaks at Receiver Dryer Cap (

A/C Compressor Failure (

Hi guys; a quick update here. So I finally found the problem. It was a relay.

12VDC 120 Ω

There’s a set of 3 of these that controls a bank of fuses, all in parallel. The fuses are for RR BLOWER, ABS/VSA MTR, ABS/VSA FSR, MAIN FAN, MAIN FUSE. Also it its known that when this fail, the AC Compressor turns ON, the relays gets hot and stop working till they get cold and starts working and failing on a loop. That explains why the main fan shuts down randomly when the AC was ON.

I replaced the 3 relays that controls Fuse Bank 1 and now everything is working fine.

Thanks for the help and suggestion guys!


Good for you for sticking with it and finding the solution. Just curious which three relays you replaced? I’m seeing several relays related to that circuit. Did all three fail, or just one of them? What was the failure mode? Stuck on, stuck off? Those sorts of relays rated for 30A and under are usually pretty reliable.

  • radiator fan relay
  • fan control relay
  • a/c condenser fan relay
  • a/c compressor clutch relay
  • IG2 relay
  • PGM FI Main Relay 1