A/C Light Blinking Troubleshooting Guide

Hey everyone, so like quite a few of you I've seen on the forums one day my a/c light started blinking on my 2007 Tacoma for no apparent reason. I figured I would share some of the information I learned troubleshooting. I'll start off by saying I'm no expert at all, but I'll try to help out people like me that didn't want to shell out the money at the dealership. What was happening with my truck was I would turn on the a/c, the compressor would kick in and cold air would just start to blow before the light started blinking. The magnetic clutch would kick out right when the light started blinking and then it would just blow warm air. So here's a rundown of everything I checked, and what ended up being wrong.

-For starters, the light blinking means that the a/c amplifier (computer control for the a/c) has detected a discrepancy between engine rpm, and compressor rpm. This can be for a large amount of reasons.

1.Compressor- If it has completely or partially seized up and the belt is just slipping over the pulley, the system has worked just as designed and is keeping you from the shredding the belt.

2.Magnetic clutch relay- This is what you would ideally want the problem to be. I've heard about lots of people having this problem, and it's super cheap. Here's a good video about diagnosing relay's https://www.youtube.com/watch?v=_gIZ0weS7iU

3.Grounds on the compressor- I've heard of the ground on the compressor coming lose and causing problems.

4.Pressures- It's always a good idea to have the pressures checked when diagnosing a/c. I had a friend with gauges do it, sorry I can't be of more help here. Also check the pressure switch on the a/c to rule it out.

5.Confirm the magnetic clutch is actually working- For me the compressor would kick in just fine for about 5 seconds so I could pretty well rule this out. You can have someone hit the a/c button while you are watching the compressor to see if this is operating correctly.

6.Compressor pickup sensor (part number 88346-04010)- Here is what ended up being my problem. There is very little info about this out there, so I'll give a pretty good run down. What this part does is detect how fast the compressor is spinning and reports that information to the a/c amplifier.

Here's what it actually looks like-


And here's the view on the compressor-


The plug is quite hard the get off, the best way I found is to come from this angle, and lift the inside tab up with a long flat head screwdriver.


Now once you've got it out, the nice thing is that you can actually test it.
Here's Toyota's method-


Be super careful when testing to not short the terminals with battery voltage. When I tested mine I got .145 volts, so if you get a very low voltage like this I would be very suspicious of this part.

-7. A/C amplifier. This would be what I would look at if all else fails. Once you have the part, it's very easy to test, just take off the glove box look straight up and unplug the old one and try the new one. The thing is, it is over a hundred dollars and basically a shot in the dark. I took this shot, so I was out the money. (If anyone wants to buy a basically brand new one for an 07 let me know) If you do go this route, be careful as they switched the part mid generation so that is something to look out for.

That is about all I can think of for now, so hopefully this information helps someone! If anyone has any corrections or something to add to the list let me know!

 

Good post!

 

Thank you!

 

I was just gonna deal with this problem by driving the rest of the summer with my windows down. Thanks for posting!

 

Thanks for taking the time.

 

@JCH When your light started flashing, did the blower continue to work? My situation sounds similar to yours: Ill hit the button, itll be solid for 5-10 seconds and then itll start blinking. while this happens the blower works on all settings its just not cooled. to me it sounds like a recharge is needed, but IDK if the truck would know that or not (i.e: send the code to flash the light)

 

Great write up man! I recently dealt with this issue on mine. After countless diagnostics and replacing of parts it ended up being I had a bad compressor that I originally replaced back in September. It was a reman or "rebuilt" one. Which I learned the hard way. NEVER buy a remanned compressor!! NEVER!! Needless to say I got a real good idea on how my a/c system works now. Oh and have a functioning a/c!

 

The blinking light means that the detected RPM of the clutch does not correspond to the engine RPM. Usually low coolant pressure will not energize the clutch at all.

 

Yep the blower worked just fine. I had almost the exact same problem. What would happen was i would hit the button, and you would hear the rpm dip when the compressor kicked in, and then a few seconds later the light would blink and the magnetic clutch kicked out. From then on like you I had air, it just wasn't cooled.

 

Nice write up. Thanks for taking the time to put this together.

 

I'll start my troubleshooting at this step. Life has gotten in the way of me actually having the tome to deal with this, Thanks!

 

This happened to me the other day. Very hot out, A/C on max. Left engine idle, for about 10 mins or so; return to truck A/C light was blinking, blowing hot air.

Turned off A/C, then back on and it blew cold air.

 

Do you still have the A/C amplifier? I need one

 

Thank you OP for posting this thread, I need to check this part out .

 

So, the engine rpm and compressor rpm are supposed to match? Before it didn’t work, there was a whining noise coming from the engine when the rpm’s increased. I wonder if that was the bearing going bad...

 

You might have saved me a lot of money. I'm in the same boat as you were. AC runs for 5-15 seconds, cold air starts coming, then kicks off and light blinks. Took it to toyota, they made sure pressure was correct and diagnosed it needs compressor replaced. But seeing this thread changes my mind on that. Plus they want 1600 for what should probably be about 700 at a local shop.

 

A local Toyota dealer mistakenly replaced a perfectly good a/c compressor(warranty work) on my 2015 Tacoma PreRunner 4.0L last summer. That said, the compressor swap out was $559.93.

Compressor $311.53 - part #88320-04060
Labor....…... $248.40

…………..……...$559.93

Is the compressor all they want to replace?

 

I think it was compressor, condenser, expansion chamber(?), then refill. Said it would be 5 hrs labor. I was amazed at the 1600 quote.

 

I have a 2013 with 85k miles and just started getting the AC blinking light. It started 3 days ago, sitting in the truck and noticed the air getting warmer, then noticed the light flashing. I turned if off and immediately back on. All was well until this morning's commute to work. Noticed the air getting warmer and the light blinking. Both times a simple push of the button made it work again. The belt is not squealing and it's been maintained by Toyota it's whole life. Do you think getting a new relay is a good place to start? It seems once the truck and AC have been running a while is when it happens.

 

Save yourself some hassle, i went through this issue and item 6.Compressor pickup sensor (part number 88346-04010) fixed my problem. i would do this first.