No power to A/C relay

Hey everyone,

New to the forum here. I just got a mechanic special 2012 Tundra SR5. The A/C does not work and gives the classic blinking light on the switch. Usually I press the switch and it never blows cold, occasionally it will work for a random length of time. I waited until it was in the right mood to not have AC at all and here's what I found:

-- The compressor spins by hand
-- If I remove the mag clutch relay and jump across the controlled terminals, the A/C works fine.
-- The mag clutch relay works correctly in a bench test
-- There is no power to the control terminals of the mag clutch relay.

Something, somwhere is not sending power to the mag clutch relay to engage the A/C compressor. Is this a common problem? If so, what is the usual cause?

Thanks in advance everyone!

 

Hi everyone,

My 2012 Tundra has a small engine shake. Enough to feel in the cab, happens from idle up to 2k RPM and maybe beyond that as well. It gets hard to tell. Has good power without shaking when driving. There are no misfire codes after half an hour of driving.

Is this the beginning of the dreaded 3UR-FE valve spring failure? I thought it only affected up to 2010, does it in fact affect 2012 tundras as well?

 

I think I’d start by checking the plugs. Depending on how many miles it’s probably due. Maybe a fuel system cleaning and the typical servicing of the mass airflow sensor and throttlebody. Good place to start at least

 

While accelerating? 30 to 40mph?? I'm getting that issue as well... but mine is an 07 at 235k

 

Maybe check your engine mounts, believe I've seen posts on here that if you like to get rowdy with your Tundie, the oem engine mounts aren't up to the task and are known to break/bend/tear. I imagine you'd feel it idle to low rpms, not when you've hit cruising speed and it wouldn't throw codes.

 

This was a Wyoming oilfield truck (or maybe a ranch truck) with plenty of cosmetic damage so I'm sure the last owner was rowdy with it at times. I'll have a look at the engine mounts.

Did the valve spring issue affect the 2012 model year tundras?

 

For whatever reason it seems to go away under load.

 

Engine shakes, but no misfire code

If you transplant a 69 Challenger hood on your truck then everything will sort itself out.




(shaker hood)

 

Maybe a low pressure switch?

 

Maybe. It mysteriously started working yesterday evening so troubleshooting is a bit off the table until I can get the problem to come back.

 

Cleaning the throttle body with a rag seemed to help. I'm going to go at it with some throttle body cleaner and see if I can get it even cleaner

 

Well, the best I can figure is that with all the things I unplugged to troubleshoot and plugged back in when I was done, one of them was a loose plug. It's worked for over an hour now.

 

Get some MAF cleaner too, do the whole shebang. Also pull the negative before you start, it will help the computer relearn the clean new air it’s able to breath.

 

Check the 10A A/C IG Fuse. The white wire coming from this fuse powers the Mag Clutch Relay.
Both pins 1,5 with the white wire will be hot all the time.

The Orange wire, Pin 2 goes to the AC Amplifier (AC ECU) under the dash behind the glove box. When you turn the AC on the the AC amp grounds the orange wire which allows the relay coil to charge up and close the internal gate. When the gate closes, it connects the 12V White Pin5 to the Red wire Pin 3 and locks in the clutch on the front of the compressor.

For troubleshooting, as long as you have 12V from the A/C IG fuse on pins 1,5 and the AC Amp grounds the orange wire, it will always lock up the clutch on the front of the compressor.

Just use a simple multimeter to check it.

If you had a loose connector, was it on the AC amp? If so this means your relay was never getting a ground signal (orange wire) so it would never close.

 

Thanks for the detailed and helpful writeup! I think I checked this fuse already and it was good.

My pet theory is that there was corrosion on the relay terminals themselves and so much plugging and unplugging polished them again. Unlikely under normal circumstances but my fusebox is special. It has two bullet holes in the lid

 

My drama queen Tundra is having another fit of drama.

The other day I was towing a ~4000 lb trailer. I was in Tow/Haul mode with the shifter at S4 just as the manual instructs. I had cruise set at 70 (this was on a highway with a speed limit of 80) and cruising up a hill, when the speed began to drop. No problem I figured, it should downshift and keep going right?

Wrong.

The engine cut out momentarily the way it does for a downshift, but no downshift. Then as the hill continued it did it again. At the crest of the hill I was going about 50 and no downshift or attempt to regain the set speed in sight. Once the going was level the Tundra accelerated (without downshifting) smoothly back to 70. I had multiple similar loads to haul up multiple hills that day and the same behavior was repeated over and over again at a wide range of speeds. Experimentally I disabled Tow/Haul mode and put the truck in Drive, but this improved nothing. I could force it to downshift and go faster pushing the accelerator, so the transmission downshifting clearly works. It also maintained a perfect 70 MPH on the flat, so cruise control clearly works, at least to a degree.

What on earth is wrong with my Tundra now?????

 

Why are you using cruise control while towing outside of flat land? I thought that was a no-no according to the manual. But I don’t tow much so not an authoritative source on anything towing-related.

I’m guessing the truck acting funky while towing and having the cruise set, using tow/haul, and sequential shifting is pretty normal.

 

Because I didn't read that part of the manual until later I recognize my error and hauled subsequent loads without it. As long as it's normal and expected behavior, that's fine. This is by far the newest vehicle I have ever owned so I'm still figuring out what is normal for something with a billion electronic systems and a CAN bus

 

I use cruise control with a trailer all the time, as long as the truck is doing what I feel is safe and how it should be acting I see no issue. Cruise control, hill comes up, it'll downshift whether it's in cruise control or not for me so no biggy if cruise control is on. That does not sound normal at all, my truck has never done that and I tow weekly, with cruise control, and up hills and on flat ground. I'll usually preemptively downshift it manually if I know that hill will require a downshift just so it's already in the right gear, but even if I don't it always downshifts on its own. Towing and not towing shouldn't make any difference in how cruise control operates, at least in my experience.

 

Cruise works with the shifter in S? That would surprise me!

The car not shifting down when in S4 would not surprise me.

 

Well it didn't make a difference when I experimentally shifted into D

 

There may or may not be anything wrong with your truck. Cruise control quality has been a consistent complaint with every Toyota product I've owned!

 

I seem to remember reading that cruise control wouldn't downshift if engine load was over some set value. Is that just a myth?

 

I am having the same problem with my 2012 tundra as well has anyone figured out whats wrong?

 

The relay will work fine for a short period and then temp causes it to stop. Replace the relay. Make sure to use the correct OEM relay. Must be OEM relay of exact specification.