A/C Light Blinking Troubleshooting Guide

yes, clutch engages about 3 seconds, then off and flashing. ive replaced compresspr sensor, compressor with clutch, clutch relay amd amplifier with no change. i also have the new toyota amplifier i would like to sell as it has no affect on the flashing light no ac problem on mine, and i assumed cannot be returned.

 

Sounds like low refridgerant

 

So you need to verify the wiring integrity of the Lock Sensor circuit between the sensor and A/C Amplifier as well as verify that the wire isn't shorted to ground.

Low refrigerant will not cause the A/C light to flash on 2nd gens, it is an issue with the Compressor Lock Sensor/Circuit.

 

I've been going through this for coming up on 3 summers. I may just get the $ and go to my Trusted Indy Mechanic. I've replaced the pickup sensor, the computer under the dash, relay, and the AC will sometimes run when it is very hot and the engine is hot so I know the clutch and Freon is good because I've measured it when running. I'm just completely stumped. I miss my 1980 carolla that didn't have anything but an engage compressor button

 

LOL, I still haven't fixed mine. I use the air all the time. I tried the relay and check the pressure levels. Blinking light came back on twice in first 3 months after the new relay, but not in last 3 months. I turn off and back on and works perfect. I assume it will eventually go, but will try the Compressor pickup sensor if it comes back. Or try to just tighten it as suggested

 

I have a 2013 Tacoma 4.0L that has the A/C light flashing, no A/C and I could use some help. FYI, this may be self-inflicted as I added an Electric Fan and around that time or shortly after is when the issue started.

A little back story. I had a new Flex-A-Lite 2nd Gen Tacoma fan setup laying around that I picked up at an online auction for $40 before I had my Tacoma. I decided since I had it I, might as well try it with the main purpose to increase the A/C performance at idle and slower speeds. The original setup used a positive trigger for the fan when the A/C was turned on. This setup worked ok except than the electric fan cycled off and on with the compressor which was not ideal.

Based on the advice in the later posts in the thread below I added an electric fan controller that would run off a negative trigger and tapped the ACID wire going between the HVAC control panel under the radio and the A/C amplifier above the glove box.

https://www.tacomaworld.com/threads/electric-fan-a-c-fan-trigger.564324/page-2#post-18819014

This setup worked great to trigger the electric fan with the A/C however this is when the A/C light started flashing. I do not remember if it was immediately after tapping the ACID wire. If it wasn’t it was soon after.

Now that we are in A/C season I need to try and figure this out. First let me say that I have no issue removing the electric fan and going back to the original setup if that’s what it takes. Here is what I have tried.

Un-tapping the ACID wire going to the A/C amplifier still yields the same results. This essentially puts everything back to the way that it was without the electric fan setup.

When turning on the A/C before the light start flashing the compressor never kicks on and the clutch doesn’t move

I have swapped the MG CLT Relay with no change.

The compressor will run and the A/C blows cold with the MG CLT Relay bypassed with a jumper. This tells me that the compressor, clutch, refrigerant, etc. are all good. Local shop also confirmed this. It appears that the issue is in the trigger signal for this relay. Is this a good assumption?

I took the truck to a local shop because I did not have time to mess with this originally and they replaced the Compressor Pickup Sensor and the A/C Amplifier with no change to the issue.

I am at a loss on what to do next. Is there a chance that tapping the ACID wire somehow blows something in the AC/ Amplifier? It seems a few people have used this method and have not reported A/C issues after.

What am I missing?

 

I would not recommend tapping anything into that circuit, the driver isn't meant to handle any current. It's only designed to be able to turn on the LED.

Do you have a test light to do some checks?

 

Yes I have a test light. Any idea what i can test coming out of the A/C Amplifier?

 

Use a needle or other suitable tool to backprobe Pin 23 (Green) at the A/C Amplifier, test light from battery Positive should light on that wire when the A/C is turned on with the engine running until the light starts flashing and it disables it.

That is your MG CLT Relay control wire (ground side switched).

 

I should be able to do that at the amplifier and the relay which would confirm if there is a break in that wire? If it doesn't light at the amplifier it means the amplifier is bad?

 

Correct, the A/C Amplifier should ground that wire to turn the relay on when A/C is selected until it times out and flashes the light.

 

So I Ohmed out the ACID wire that I tapped (Hvac control panel to A/C amplifier) and the green wire from the A/C Amplifier to the relay just for the heck of it and both teated good.

The original A/C amplifier does not light up the test light when hooked to positive battery and the back side of green wire 23 going to the relay with the engine on and A/C on.

The new A/C amplifier however does light up as you described it should till the control panel light starts flashing.

But with the new amplifier the I still get the flashing control panel A/C light and no A/C

To me this means the original amplifier is bad but there is also something else still wrong or bad.

 

Does the compressor come on briefly before the light starts flashing with the new amplifier though?

 

It does not. The engine RPM change slightly but the clutch never engages.

Also with the relay out and the test light I get the same at the relay as the amplifier.

 

So we're still dealing with a control side issue.
Have you checked the control pins at the MGCLT relay? One should have power with the key on and the other should be grounded by the A/C Amplifier when A/C is selected.

 

One side does have power

Yes both sides of the relay have one hot wire when the truck is running and the control side goes to ground when the A/C button first turns on. Both ends of the green wire pin 23 on the A/C amplifier are doing the same thing.

 

And if you jump pins 3 and 5 (larger pins) of the relay the compressor turns on?

 

Yes with the relay removed and a jumper between 3 and 5 the compressor turns on and A/C blows cold.

 

So it would seem you have a bad relay, you seem to have everything you need there.

 

I have swapped it with a few others and they all act the same. One of them was the horn and the horn worked with the A/C relay installed. Unless I'm missing something that should rule out the relay being the issue I would think.