AC help !

Hi, new here. Having some A/C issues. Vehicle is a 2017 TRD sport crew cab with the 3.5L (2GR-FKS) 6MT 4wd.

The A/C shuts off after about 2-3 seconds of being turned on, though occasionally works and blows cold when it does, but always eventually shuts off anywhere after 1-30 minutes. The compressor has been replaced, with no change in symptoms. Leaning towards an electrical issue. Does anyone know where accessible connection points for the pressure switch and temperature sensors are and testing values? Locations of the sensors/switches themselves would be helpful also. Seems like maybe the temp sensor is built into the evaporator in the dash, but beyond that I can’t find any info online, google is being useless.

 

The A/C light turns off when it shuts off?

 

Yep. Shuts off completely, light & all. Turns right back on if I hit the button, but shuts off again after a couple seconds.

 

See if the compressor comes on for a few seconds when you turn it on, if it does and then shuts off along with the light you have an issue with the compressor Lock Sensor and/or Lock Sensor circuit.

I can post the wiring diagram but I need to know if you have manual or auto temp controls.

 

It definitely turns on with the light. This is what the controls look like, auto I suppose ?

 

Yea that's auto.

The A/C Amplifier is behind the glovebox, need to check the Lock Sensor and check wire integrity between the Lock Sensor and A/C Amplifier.


You can check between Connector A35 Pin 7 (Green) and Connector A36 Pin 28 (Light Green) with the Amplifier unplugged, should equal the same resistance as the Lock Sensor.
Also check both wires for a short to ground.

 

My 2006 Taco had a similar AC failure. The problem was the tachometer on the compressor was bad. Its a bolt on replacement item but hard to find.
The tachometer output on the compressor is compared to the engine RPM and if they do not match, within limits, the AC will shut off after a few seconds for safety reasons.
Example; Say your compressor locks up, you want your clutch on the compressor to release or you will burn up your drive belt and your motor will overheat because your water pump cannot work
without a belt. Most Automotive AC Systems work in this manner.
The Stealership wanted to replace everything and charge me about $2k. I researched and figured it out on my own. The signals (engine and AC compressor RPM) are compared on a circuit underneath the dash.
The replacement Tach was about $100.

I sold my 2006 Blue Taco pictured. I have a 2019 White TRD Pro now.

 

Yea that's what we're after, compressor has already been replaced I'm assuming it came with a new sensor. Doesn't mean it's good but we have to test.
Unfortunately the lock sensor isn't a simple replacement on 3rd gens, you have to recover the refrigerant to replace it and then recharge it.

 

Thank you! That’s super helpful. I’ll hopefully get around to check those tomorrow.

 

One word of caution don't shove your meter leads into the terminals, if you can't touch them with your leads use a needle, backprobe, or other suitable tool. Never stick anything into it that's larger than the male pin or you will spread the terminal.

 

@Dm93
@coolreed

Impressive trouble-shooting!

 

Thanks, one of my old instructors at tech school taught me how to make back-probes out of wound electric guitar strings, they work surprisingly well. I got some lying around I think…

 

Hopefully we can track this down pretty easy, the best way to check the lock sensor is with an oscilloscope but that's not an option for the average DIY and even most shops don't have/use one.

 

Was the compressor replaced because of this issue, or like months/years ago?

 

Sure was. I brought it to a shop early last summer. They actually put TWO compressors in it, but the problem slowly came back. AC almost never works now.

 

Ok so the problem began and a shop replaced the compressor. AC then worked for a while and then bam, same issue as we have now right?
To me that sounds like something is causing your compressor clutch to either not engage at all… or something else in the system is triggered when the compressor works for a few seconds and then turns it off.

 

Haven’t checked the lock sensor yet, but I’m getting a reading of about 700+ ohms at the connectors to the AC amplifier. I’ll see if I can get underneath soon and check at the compressor

 

So I think I got it all sorted out through a couple of breaks at work. Was pissing rain yesterday so I started in the dash, tested pins @ AC amplifier, .725 Mohms- not good. Got underneath just now in good weather, 185 ohms @ the compressor. Figured a broken wire, just for shits and giggles I reconnected compressor and retested @ amplifier, 185 ohms. Ran out of time but it was running just fine for a solid 8-10 minutes. Maybe the connector just wiggled itself loose enough to have bad/spotty continuity @ the compressor? Either way I’m happy ! Thank you guys so much for all the help !

 

I wonder if someone in doing previous testing shoved their probes into the connector and spread the terminals, I see it fairly often. You never want to put anything larger than the male pins into the female terminals or you will mess them up and they won't make a good connection anymore.

Standard Motor Products P/N S2533 if you end up needing a new connector.
https://www.rockauto.com/en/catalog...ical-connector,a/c+compressor+connector,10356

 

It’s possible ? The one that was possibly loose was the one on the compressor. Straight male pins on the compressor side(which is where I tested). Unless someone was checking the continuity of the isolated wires. I’m thinking the shop just never *fully* clicked the connector in (kind of a pain to get to, not a lot of space) and it eventually just wiggled itself to the point of making a bad connection on one of those two pins. Either way, it works 100% now, so I’m happy! Just need to put the dash/glove box back together.