Heater rear defrost light flashes on start up and rear heater clicks

After putting in two new actuators the clicking stopped and everything worked for a couple of weeks then it started clicking again . thanks for your advise.

Hi Dan,

I need to get a clear idea of exactly what we are talking about. When you say actuators, are you referring to the air flow or temperature actuators? When you say defroster, it is the rear window defogger grid? If it is all related to the grid unit, have you checked the relay? (See picture 1).

Next, I need you to pay attention to the flashing. Is it a specific number of flashes each time? One last thing, do you have access to a scan tool that can read HVAC codes?

Let me know.

Joe

Thanks for your advise. Will the relay make this click like it does? I don't have access to a scan tool for HVAC. Yes, its the two actuators you mentioned that I changed. I haven't counted the flashes but it flashes quite a bit before the heater in the front comes on.

If we had a scan tool, it would most likely indicate where the problem is coming from. Without it, we have to try different things.

The first thing is the relay I mentioned. Lets check that. If there is another relay with the same part number, switch them to see if it changes. If there isn't, here is a link explaining how to test a relay:

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

Here are a couple links you may find helpful:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

The interesting thing is that it worked properly for a couple weeks. Does it eventually start working now?

Joe

The blend door at the back for top vents to bottom works but the temperature from hot to cold is stuck on heat! When i put the new actuator in they both worked properly not the temperature door isn't working because it is hot all the time but it's the clicking when i start the van that bothers me.

I checked everything before i put it back together and both doors worked fine.

I will check the relay and if that doesn't fix it i will get it scanned somewhere.

If you have any other ideas i would appreciate it. Thank you so much for your help Joe.

I have to be honest, since you are hearing a clicking and it is stuck on heat, I suspect the actuator has failed again. They are so cheaply designed. Chances are the teeth on the actuator have stripped.

Let me know what you find.

Joe

Okay, i used a Dorman and i heard they are not that good so i will use a Chrysler one next. Thank you so much for your help Joe.

Thank you for your response Joe. Yes, i replaced both actuators that you mentioned and yes it flashing light is the rear defroster light on the front control that flashes.Will the relay make it do the clicking each time the vehicle starts? I don’t have a HVAC scanner.

I have a 2014 Ram 3500 Limited and I had this happen at the same time my brothers '16 Charger had the same problem.

In my truck the mirror defrost button (i mistakenly thought this was my rear defrost button which my truck doesn't have) started blinking and didn't stop. While this was happening I couldn't change anything on my HVAC except fan speed. I couldn't even turn it off.

I took the truck to the dealership & the only remedy they could offer was flashing the ECM. I agreed & $115 dollars later it was still blinking. They then suggested that they could pull the whole dash & check the blend & recirc doors. I declined.

I pulled fuses, unhooked the battery - no fix. Same for my brother & his Challenger.

I finally changed the HVAC Control Module. OEM was $100 & the only tool required was a phillips screwdriver. The process took 10 minutes start to finish. I started the truck and the light started blinking but I held my breath. After the truck went through all its self checks, the light went off & all my controls worked. J did the same on his Challenger and his went back to normal as well. The light is the computer's way of telling you that self diagnosis has failed.

Apparently the module's memory can fill up and cause it to fail. Sometimes pulling the battery will cause the same thing.

Hi,

Thank you for that post. It's excellent. I know it will help others.

Take care and feel free to come back anytime in the future.

Joe