Failed AC amplifier?

Anyone encountered a failed AC amplifier before? I see lots of posts regarding AC, but nothing really pinpointing this component.

I have a 2017 tundra with about 60k. I had my AC clutch replaced under warranty because it was squealing away. Months later, outside of warranty the AC failed.

I found a blown fuse in the magnetic clutch circuit. I replaced and made the light stop flashing, but system still wouldn’t pick up. Freon was also low. After a recharge and leak stop it seemed to be working fine.

A couple weeks later the fuse blew again. I took it to Toyota hoping they could do something with goodwill. They suspect the ac amplifier, but don’t have a good one to test with and said electronics need to be paid for upfront. The amp is over $1000 and they haven’t made me confident it’s the issue.

Any similar experience with Tundra AC?

 

I have done 50 AC replacements in a variety of a cars and trucks (never a Tundra) but plenty of Toyotas and never heard of an AC amplifier. Clutch is electric. Only reason it would be blowing a fuse is coil in clutch is shorted or power supply to clutch is damaged. Usually if coil in clutch is bad it doesn't engage, it doesn't blow the fuse. The Toyota clutch's I changed were a 10 minute job. You didn't even have to evacuate the system. Some GM's you do. Amazing my 2001 Lexus uses a variable displacement compressor so the clutch doesnt cycle, work beautifully, but my 2021 (20 year newer Tudra uses an 1980's style clutch) that cycles....

 

I googled it, it is the brain control for you AC unit. I would ck ebay or salvage yards. There are millions of tundra's so used parts should be readily availabe

 

I have a pretty good sense of what it is. It’s sort of a logic controller for the hvac system. Inputs are a a variety of sensors and controls (pressure, temperature, etc.) and the outputs are signals to engage the compressor, operate servos for vents, etc.

The trouble is I don’t have access to tech stream or any way to interrogate it. It’s basically a black box. I don’t know if the sinking transistor for the clutch is fried or if there’s a line of logic that’s blocking it from picking up.

I’ll see what I can find for salvaged parts, but I won’t really know if it’s the fix until I’ve bought it and installed. Part of the trouble with electronics that offer no diagnostic options.

 

Mine failed on my 2014, 75k mi IIRC. Covered under my extended warranty

 

I would start with an extensive search of Tundra AC issues. Every vehicle has their weak points. The low charge level seems odd to me. Do the Tundras use a desiccant type dryer in the AC system? I had another vehicle where the desiccant bag blew up and the charge level would register as low. When charged up, the system would then allow the AC clutch to engage. When engaged with the blown up desiccant bag it was not a sound you would want to hear.

 

clutch is easy to test. Apply 12 volts to it, you will hit it click in.

 

Clutch tests fine when forced through tech stream, but won’t pickup with AC turned on in normal operating conditions. Resistance measures good on the coil. No codes.

 

I bet the AC amplifier was used in a number of different toyota models and can probably had pretty cheap on used market. not a fan a replacing parts but if cheaper than diagnostic fee why not. My lexus needed a shift solenoid, dealer wanted $500 for part. In the end said car wasn't worth repairing as they like to replace them all, no its not worth 2500 in parts plus labor I agree. I got one out of junk yard $10. Transmission shifts perfect again...

 

The Tundra uses a specific model AC amplifier (ECU basically) for each unique CAB CONFIGURATION and TRIM LEVEL. I know this from doing the "Auto-AC Climate upgrade" in my 2008 SR5 Double Cab. There have been part number changes over the years, so some of it will depend on your specific year as well, but typically you can go to a newer part as long as it matches your cab and trim.

Go to https://www.car-part.com/ (nationwide used salvage yard search) and put in the parameters of your truck, choose interchange search for the same trim, and the part you are looking for. You should be able to get them for ~1/2 or less of what the dealer wants for new.

Another helpful site is https://www.toyodiy.com/ If you have the part number of YOUR AC amplifier, you can plug it into the cross-reference here and see any other makes/models/years that use the same part. That sometimes helps you broaden your search for other options. I once did that when looking for the solar sensor to update my 2008 to have auto-on headlights. The same sensor was used in older Sienna minivans (and a lot of other vehicles) and I was able to find one at a pick-and-pull for free.

I can also help you with finding the EWD for your specific year AC system, which will show the other items that are on the same fuse that keeps blowing. In 300k miles on the truck (150k with original climate controls and another 150k with the upgraded controls), the only issue I ever had was having a damper door servo go out, which caused the Auto-AC system to keep resetting itself and (obviously) made it so it wouldn't change modes.

 

Here's the wiring diagram for 2016/2017 AC system.

 

Wow, fantastic information!!! Thanks

 

Thanks for the wiring diagram. I only had a 2015 version which I assumed was the same, but I see between that time they added a suppression diode across the coil of the clutch. Is that showing the diode is internal to the clutch?

 

Any update on the amplifier/the issue you had? I’ve got a ‘15 that had the a/c compressor replaced 15k miles ago and worked great until a few weeks ago. Now the clutch engages for about 3 seconds and blows cold then the clutch disengages again. The mechanic that replaced the compressor did some digging and said the amplifier needs to be replaced. I want to verify the amplifier is bad before I hunt one down, any input would be greatly appreciated.

 

Report if you changed AC Amplifier (AC ecu), and symtoms

Thank you

 

So I ended up finding a used amplifier and it didn’t fix the issue I had. So I then got a diagnosis from a different mechanic. Turns out the aftermarket clutch was just junk. Moral of the story, use quality parts.

 

That is interesting. I had to threaten the dealership with attorneys to get them to honor the warranty and replace the compressor that they claimed was the problem but they refused to change the clutch. I don't want to begin diagnoising it myself because by doing so may give them the opportunity to void the warranty. So after replacing the a/c compressor clutch with an OEM clutch, your compressor no longer cycles from engaged to disengaged every 8 - 10 seconds anymore??? Does it now stay on for approximately the same duration as it does when the blower is on max??? Maybe that information may be enough to convince them to complete the repair and replace the clutch like they should have in the 1st place. If not, I may have to attempt to obtain a log file from my scan tool to prove it. It's always so easy to purchase extended warranties but a nightmare if you make a claim. Thanks for your help!

 

My a/c system now functions perfectly after replacing the aftermarket compressor/clutch assembly with the factory compressor and clutch. The clutch that came with the aftermarket assembly just wouldn’t stay engaged, the compressor was actually fine. Sorry to hear you’re dealing with that kinda mess, in my experience the only good extended warranties are the ones you get through the factory. Even then though sometimes those can be problematic. Best of luck!

 

Thanks for the information. I just went to the dealership. I have an appointment to bring my truck in Monday morning and I don't think I will have any issues with them honoring my extended warranty this time because they seemed to remember me from last visit. My extended warranty is through Toyota; I think the issue was just an incompetent service person. lol I'll post the outcome next week for anyone else having the same issue as we have had. Thanks again for the info...

 

Any good news?