A/C Light Blinking Troubleshooting Guide

You have to be missing something then, are you using a LED or incandescent test light?

 

Incandescent

 

Then you should be able to trigger the relay by connecting it to ground and touching the control wire at the A/C Amplifier.

 

I'm not sure if this is what you meant but with everything hooked up and backpinning the control wire to ground it did not turn the compressor on like jumping the relay at the relay did.

I have to go out of town. For a few days so this is my best chance to have someone look at it. I have removed the electric fan and am likely going to drop it off at the local Toyota dealership tonight. I appreciate all your help. I'm just not getting anywhere on my own unfortunately.

 

Well if the relay is good, everything is good on the load side, the A/C Amplifier is grounding the wire, and your on the right wire you have to have an open in the wire somewhere between the A/C Amplifier and the control side of the relay. Pretty simple logic, You can split the circuit in half by checking it at Connector IA1 Pin 31 (Green) behind the left kick panel.

 

Yesterday I Ohmed out that wire from the amplifier to the relay and it's solid.

 

But did you load check it? Ohm test is fine for checking some stuff but it can get you into trouble checking wire integrity, a single strand of wire will show a good ohm reading (or voltage reading if your checking voltage) but it's not gona carry any current once you put a load on it.

Very good example in this video, circuit shows good voltage but won't carry any current.

https://youtu.be/LGts5gWsLOc

 

I didnt get a chance to test this with load but I did learn something interesting. All of my testing has been with the truck at idle. I went for a drive and the A/C light stayed solid and I had cold air coming out of the vents. But at a stop sign it started flashing again. What I found was if I kept the RPM above 1500 the system was happy. As soon as I dropped below 1500 rpm it would start flashing. I'm guessing I now have a compressor or clutch issue.

 

^
Wait you said the clutch wasn't coming on at all with the relay plugged in, now it is?

 

That seems to be correct. At just idle it never came on or moved. I had it marked with a paint marker.

 

Something fishy is going on then, I think we need to re-visit this.

You said the idle changed which tells me the ECM saw the A/C request from the A/C Amplifier so that means it commanded the clutch on but the clutch didn't turn on.
Now it turns on but doesn't stay on under 1500RPMs?

 

Well I think it's coming on. With the engine RPM above 1500 the light doesn't flash and it seemed like the AC was on. I guess I don't know for sure because I was driving and it is in the high 40's here today so I guess it could have just felt like the air was on. So I guess there is a chance that the compressor was not running. Why would the AC light stay solid above 1500 RPM if the compressor was not running?

 

That I can't tell you, all the testing I've done on mine to get know good data has been at idle.
Can you duplicate it sitting still and see if the compressor is on?

Maybe an experiment is in order when I have time

 

Unfortunately it's at the dealership now so I can't do any more troubleshooting.

 

Well good luck, hopefully you win the tech lottery and get one that knows how to diagnose it instead of throw parts at it.

 

Well it's fixed. Wrong relay was in the magnetic clutch relay position. The dealership swapped the horn and clutch relays and all works as it should. It appears the issue all along was the amplifier but in troubleshooting the other shop I took it to swapped relays I guess. Why the light didn't flash over 1500 rpm still confuses me but I have cold AC again and it didn't cost me too much at the dealership. Im still unsure if the electric fan trigger was what caused the amplifier to blow or not. I liked having the electric fan as it was quieter and the AC worked great at idle. I may try it again at some point if I can find a different trigger.

 

Id use the wire going to the clutch as a trigger, that's how the factory condenser fan is wired on the Mexico models and no risk to blowing up modules. Worst case you pop a fuse.
Easy to access in the underhood fuse box at Connector EA1 Pin 3 (Violet).

 

I think if I was doing an additional fan like the Mexico models have with the mechanical fan still in place that would be ok. With only an electric fan when the compressor cycles off the fan goes off unless the vehicle is calling for cooling. I have read that's not good for the ac system to not have air moving across the evaporator while the ac is on and the compressor is off during its cycles. Maybe it's not an issue as most times you will be driving so air is still moving.

 

Many vehicles with electric fans only run them when the compressor is actually on, some don't even turn them on until the pressure goes above a certain threshold and/or the coolant temp goes above a certain temp.
As long as they come on with the compressor your fine.

 

Good to know