A/C light flashing

When the system blinks it usually means you are low on charge. but to be sure here is a guide to help walk you through the service:

https://www.2carpros.com/articles/air-conditioner-how-to-add-freon

Please run down this guide and report back.

Cheers, Ken

That's not right did you have it connected to the low side? Can you upload a picture of the port used? The system is overcharged? Check out this guide.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Please run down this guide and report back.

Thanks FLOBS for the addition to this post as that is good info.

You are correct that a flashing light does not directly mean that the system is low on charge. Meaning if the light is flashing then you need to add freon and that is the only solution.

However, Ken said it "usually" means it is low on charge and this is accurate.

The flashing light means that the HVAC control module has shut off the compressor because it is seeing an issue that could damage the compressor if it continues to run. This includes high and low system pressures or any of the issues that you mentioned as well.

On this site, the most common cause of A/C issues is by far incorrect charged systems. This mostly started when the "DIY fill cans" became popular. The reason is, when people have an A/C issue, they get a can and fill their system assuming that it is low and then they overcharge it.

So we have found that we need to start with checking the charge of the system just to make sure that is correct before we get down the road on something else.

This vehicle has a dual pressure sensor so if the system is low or high it will tell the HVAC module and it will cut the compressor. However, it will flash the AC light if the charge is low enough that the switch cut it off.

In this case, the member informed us that as soon as they put the gauge on it went straight to the red, which means it was overcharged and most likely tripped the high pressure switch and the module cut the compressor. At this point, it will flash the A/C light telling you that it cut the compressor due to an issue.

While we don't know the result as they never came back, it is pretty safe with that info to know he probably corrected the pressures and it corrected the issue.

You are correct that this can also be due to an electrical issue or sensor issue but there is not one correction for this flashing light.

Because of that, it is advisable for anyone who has a flashing light or other A/C performance issue to start with checking pressures. This is just a basic system check that can often put us on the right path if the pressure is correct or not. No different then telling someone to check their oil level when the oil light comes on.

Let us know if there are issues we can help you with in the future. Thanks

Just to start, have you confirmed your pressure is correct? Or at least jump the compressor with 12 volts and see if it comes on and blows cold. That would be a good indicator that this is okay. If it is and this is happening then you are on the right path that this is most likely something to do with the amplifier or the amp itself.

So based on that, we are going to have to check the voltages at the AC amplifier with the AC on. Basically we need to see what voltage is there and then that will tell us what direction to go. It is much more effective then just inspecting the wiring or checking different circuits looking for an issue.

We need specific voltage at the AC amp in order for it to work so let's see what we don't have and go from there.

Okay. So when you are testing pin 12 to pin 8 for voltage, you are doing what is called a voltage drop across whatever component is on this circuit.

So you are finding that the Evap pressure sensor actually uses.58 volts to operate but you are not finding out what the sensor is telling the AC amp. To find out what the sensor is telling the module you need to check pin 8 to ground.

The way that circuit works is the pin 12 is a signal circuit which should be 5 volts. Then this 5 volts passes through the evap sensor and returns to the AC amp where it tells it what the temp sensor is reading. This will be on a scale from.5 volts to 4.5 volts due to the sensor requiring a small amount of voltage to operate (which is the.58 volts that you are finding with the voltage drop test).

So we need to see what the volt is from the sensor using this test and we can go from there. The same pin 10. You are getting 0 volts because this signal circuit is not connected to the clutch so it is basically an open circuit.

The problem is, these wiring diagrams are not exact to your truck. We don't have one for this specific vehicle so this is going to continue to be confusing until we get one for your vehicle.

Thank you for the update. Based on that, I think you are right on it.

Please let us know how this turns out.

Thanks again.

That is great! I am sure this info will help others. I totally understand but you did an excellent job in sticking with this and saved yourself a ton of money in having a shop figure this out.

Thanks for sticking with us and keep us updated with what you found.

Please come back in the future.

Hi,

I'm sorry, but the person never replied with that information. This model isn't offered in the US, so I have no pics of fuse boxes.

After reading through everything, the fuse box in question will hold the relays for the A/C compressor clutch and the condenser fan motor. Are you able to locate those things?

Let me know.

Joe