AC Compressor will not kick in

If you jump the pressure switch and it works you most likely have a bad pressure switch.

 

For what it's worth, different compressor, different vehicle, but looking at my video, the Sanden compressor for the Honda was kicking on at 46psi. It was about like yours, upper 80's/low 90's before I shut it off and started reading.

 

Well, I wasn't able to find an AC compressor clutch relay in the fuse box, it may be located elsewhere. I did notice that the pressure in the low side changed in the last 23 minutes.
It was here
20210823_123046 by Jose, on Flickr

It is now here
20210823_131544 by Jose, on Flickr

I wonder if that's a leak or if it's temperature fluctuation, although a perfect vacuum shouldn't have that... too many theories and concepts in my mind right now. I will focus on the electrical lol.

 

Probably in your PDM ("Fuse box") under the hood; it will look like a regular fuse, except it's likely solid black, and you won't see the fusible link. Should have a "1.0" or "1 Amp" and the diode schematic. If it's fully open in both directions, it's bad and needs to be replaced, but based on the post you just made showing the drop in vacuum, I'm guessing your issue is on that side.

 

Assuming your gauges connections are good, I think that's a leak. Just keep an eye on it a little longer. I don't think a system temp change could do that, but it should level out if so. A leak won't.

Did you put some PAG oil on the O-rings when you put them in?

 

On that note, did you balance the level of oil in the system when you replaced components? Depending on the brand, the compressor may have come with no oil in it, or all of the oil for the whole system. If you left oil in the components you kept, like the condenser and evaporator, and the compressor came full of oil, you would need to remove the appropriate corresponding amount of oil from the compressor. If the compressor came dry, you would definitely need to add oil. I don't have the specifics for the amounts. For the Honda, the values were in a service manual.

 

1st gens don't have a compressor relay, it is controlled directly by the A/C Amplifier.
The Amplifier has to see 4 things for it to turn the compressor on.
An A/C request from the switch (12v)

A signal from the pressure switch (12v)

Evaporator temp sensor reading above about 34 degrees (I don't have the temp/resistance chart handy, maybe someone can post it)

And an A/C allowed signal from the ECM.

If any one of the above is missing or incorrect, it will not allow A/C operation.

 

Yep, I lubricated each O-ring with the PAG oil before putting it in.

So the compressor came full of oil but had instructions on draining it and refilling which I followed. It's basically the same process outlined in adventure taco's page
https://adventuretaco.com/guide/replacing-the-a-c-compressor-on-a-5vzfe-tacoma-tundra-4runner/
I'm pretty certain that wouldn't stop the clutch from engaging though. Years ago, I installed a new compressor and left the oil at the level it came with and it ran perfectly for years.

This is good information, I will address my leak and then try the pressure switch.

 

Awesome. Just passing along thing I had learned. I think DM93 has you on a good route. Good luck.

 

So, I tried jumping the clutch to the battery (with the truck off) and sure enough, it clicks and engages. I tested the connector and there is no voltage at it when the truck is running/ac on. When I jumped the pressure valve connector, I do get voltage at the compressor, but the voltage readings are nuts. They keep climbing higher and higher and even if I connect the compressor, the clutch will not engage.

 

What is the voltage with the compressor plugged in?

 

With the truck off or the pressure switch not jumped, I don't get voltage. When I test at the connector for the compressor, with the pressure switch jumped, I get crazy readings up to 300V. It keeps changing though. Do you mean to plug the connector back into the compressor and measure the voltage once plugged in? I can try that and see.

 

Yes

 

Any chance your meter needs fresh batteries? That makes NO sense at all.

 

In order to test this, I had to put a wire in between the two halves of the connector as the rear of each half is sealed where the wire comes. Now, even with the pressure switch jumped, I'm actually getting no voltage at all on either end of the connector. If it isn't the pressure switch, does this mean my amplifier could be bad?

 

Could be a broken wire as well, was the compressor working prior to changing all the A/C stuff?

 

Prior to changing everything out, it was the same deal. The old compressor would not engage the clutch either.

 

Pin 9 Black/Yellow at the A/C Amplifier should be the clutch wire, see if you have battery voltage on that wire at the module with the compressor plugged in.

 

Alright, I tested it out and got 130 mV or basically nothing. In other news, I feel like my voltmeter is a little nuts.

 

I also tested the #5 pin from the AC switch and it has 13.8V with the pressure switch jumped or plugged in.