A/c clutch relay

Sorry forgot to post tundra is 2005 quad cab 4x4 4.7.

 

Mind being a little more explicit Steve, do you have a problem ?
There is no A/C clutch relay but there is a Heater relay that when energized supplies current to the magnetic clutch that causes the compressor to operate.

 

Yeah, the Ac stopped working. It's my friends truck. Theirs just vent air, and the ac clutch doesn't engage. The relay your speaking of, what number is it on under hood fuse box? Thanks.

 

If vent air is working it's not the Heater Relay. What I would then check is the 7.5 A A/C fuse in EG bay. In case you need to know, I've marked the Heater Relay but also the A/C fuse.

 

Stupid question, but have you had someone throw gauges on it to test high/low side for pressure?

On most modern vehicles I've owned, if there's insufficient pressure in the lines (i.e. coolant is low), there won't be a signal sent to kick on the clutch. Self preservation.

Of course, you want to check both fuse/relay boxes, under hood and in dash, but ...

 

While low fridgerant is definitely a possibility, it does not prevent the magnetic clutch for compressor to operate. It will simply short cycle, which is usually an indication of low freon.

 

If it’s low enough, like from a rock to the condenser, it will be below the threshold to close the switch

 

If it's a big enough rock, A/C working may be least of there problems

 

Boy I'll say. That big of a rock would rock you to sleep. No I haven't thrown my gauges on it yet. Like bubba said the clutch would repeatily cycle on and off. It's not cycling at all. And my friend Eddy said it was working fine then nothing. I will throw them on and check low and high side. What kills me is everything on internet says fuse box is marked mag clutch for relay. Thanks for replies guys. In all my years of wrenching nothing ever goes easy, when it does that's when I'm suspicious. Like Ben Franklin said, he expects the worse, and when it doesn't happen he's pleased. What can expect getting zapped by lightning!

 

Yup. I mean, don't get me wrong, I'm not an HVAC guy so don't listen to me. It's also possible Toyota is different. I know with most of the 4.8/5.3/5.7/6.0 SBC I've dealt with, there are low pressure, high pressure and cycling switches, and the simple test of, for example, jumping the low and cycling switches temporarily told me pretty quick low pressure was my issue on my last truck where the clutch wasn't budging, as if it was frozen. Wasn't the clutch at all, freon top-off got it running again, dye showed the compressor was leaking.

I mean, it's totally possible the compressor clutch is seized up. There's a number of things you could potentially check out to confirm though, but you may've already done. Checking harnesses, checking both fuse/relay boxes, checking pressure. But I'm assuming there's something you can jumper on the 4.7 that'll tell the compressor to engage.

 

Definitely jump out the low pressure switch as a quick test

 

When I get truck again after checking fuse and relay is to pull plug at ac clutch, and check for power. I've got a sneaking feeling it's a power/ ground thing. Expect for the 20 amp relay we replaced Sunday, the others should be swappable.

 

Well guys, Mr shifty wins the prize for diagnosing the no AC problem as low/no freon. I was working blind with no schematic. My buddy Eddy took his truck to his regular mechanic, and he pressurized his system. He found no leaks, which is weird, but said freon was depleated. The one thing I never did, since the clutch wasn't cycling on and off as is normal with low freon. $360.00 later he's got cold air. For any readers out there with Toyota, or any make, check that pressure reading. I've been wrenching for over 50 years, this is a first for me. Thanks to all that contributed to the troubleshooting of his vehicle. Moose.

 

Holy shit, I got something right

Seriously though, you're not the only it was a 1st for. It was a 1st for me once too, I didn't see it until after a couple of decades of turning wrenches myself. Possible it's just a 'new car' thing because I don't recall ever seeing it on anything American-made I ever drove or worked on pre-1990s.

That is weird there's no leaks. @1955moose is it possible one of the Schraders has a slow leak, needs to be tightened? I'd have assumed the person who put gauges on it would've checked, since that's the only other logical leak point but it would've probably had something hooked up to it at the time, maybe?

 

Yeah shifty it's a weird one. The truck is 17 years old. That's new to me. Ac is a simple yet complex system. Just like automatic transmissions. Years back I worked at a taxi company. The shop manager said he used to have a great mechanic that knew how to diagnose and repair the tranny's on Ford Crown Vics. He hasn't found one with his knowledge since. That was back in 2009. Again thanks for the diagnosis, hopefully it will help in the future for another member.

 

This solved my issue too, partially. My ac stopped working in my 05 SR5 and couldn't find a blown fuse or anything like that. Just blowing nothing but hot air and the clutch wasn't engaging. I dumped more refrigerant into it and it started working again. I'm sure there's a leak somewhere that i need to have looked at and fixed but that's still cheaper than having a compressor replaced lol. Thanks guys