Another AC problem

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Spareparts

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No, just under the hood. When i replaced it all under the hood the only lines remaining were from the rear ac.
The rear ac also blows really cold air when the ac is jumped to run.
No i did not replace the TXV valve. It seems to be working fine.
 
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1998_K1500_Sub

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No, just under the hood. When i replaced it all under the hood the only lines remaining were from the rear ac.
The rear ac also blows really cold air when the ac is jumped to run.
No i did not replace the TXV valve. It seems to be working fine.

That's very encouraging that the rear seems to be working well.

Was the original orifice tube's screen clean when you removed it? The TXV has a similar screen, so if the old orifice tube's was clogged with debris, the TXV's is likely the same.

I'll study your other posts, maybe I can shine some light on your problem.
 

1998_K1500_Sub

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Tried the test above and at both spots the test light comes on dim and the ac pump turns on

Describe your "test light" please. One man's "test light" might be another man's 55W 12V bulb. Size matters.

Here's a relay connection diagram for reference. I may refer to this, later, assuming your AC relay is of this type.
 

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Spareparts

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Thanks.
The old orifice tube under the hood was clean but had dirty old gray oil on it.
Test light it just like this but about 40 years old and yes it does work. Tested it at the battery.Here
Yes both relays i tried are like the picture.
 
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1998_K1500_Sub

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Charged it with proper amount of oil and R134A, 3Lb 8oz
Interesting. The 1998 service manual, and the sticker on my 1998 Suburban, both indicate a charge of 4# of R134a.

You must be registered for see images attach


AC blows cold when the system is on both front and rear.
AC Clutch will not engage unless i jump it at the pump with 12v or jump it at the relay. Fuse is good.
It will not turn on if i jump across both pins on the low pressure switch on the dryer.
The low-pressure switch has one side grounded (normally) and the other side connected to the VCM. Use your test light or a DVM confirm that one terminal of the the low-pressure switch's connector is grounded, and report your results.

There's more about this switch, below.

If i jump the high pressure switch? at the compressor it does not come on but the AC fan on the condenser comes on.
Good. Is this with the dash set to AC?

With the high pressure switch jumped, the system should also go into recirc mode. With the Suburban, when in recirc mode the water valve (RH side of engine, in the front heater's coolant lines) should be actuated by a vacuum signal (vacuum hose) from a electro-mechanical vacuum switch located on the firewall. The solenoid on that vacuum switch controls whether vacuum is applied to the water valve. This is not critical now, just mentioning it. The vacuum switch can become plugged; I cleaned mine with Brakleen. The vacuum motor on the water valve can fail, too.

When i check both pressure switches with a trouble light none have power. I think the low pressure should have power??
The high-pressure switch is working, it appears, based on the results from when you "jumped" it. This also suggests the VCM is somewhat sane, as it's responding to the switch. Confirm for me: The high-pressure switch you speak of is the one mounted near the AC lines' aluminum block that bolts to the compressor, yes? I'm just confirming, as there's another high-pressure switch on the back of the compressor.

Regarding the low-pressure switch, check it for ground as I mentioned above. Make mental note of which terminal on that connector is the "grounded" one.

Now, let's talk about the other terminal on that low-pressure switch connector.

A wire from that terminal is normally connected to the VCM (see the electrical diagram posted prior by @HotrodZ06).

You can try to measure the voltage on that terminal when the dash controls are set for AC. If the VCM actually applies some "power" to that terminal, it may not be enough to illuminate your test light. You might use a DVM to check for the presence of voltage on that terminal (it might be +5V, it might be +12V, it might be anything other than zero).

If you connect that terminal to ground, the VCM will typically engage the compressor if the dash controls are set for AC.

(note: check back for edits, as I'll probably add more to this)
 
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Spareparts

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More info.
The water valve was replaced about two weeks ago. I never tested it for function but it is hooked up proper.
The compressor had 6.5oz of Pag46 in it. I added 4.5oz Pag46 with UV dye throughout the system

On the top of my old dryer the sticker for suburban said 3lb 8oz so i had 5, 12oz cans of R134A and put 4 3/4 cans in. I don't remember the pressure readings but they were in the range for 70deg as was the temp outside.

HP switch is as you describe. There is no switch on the back of the compressor nor can i find a plug anywhere unused.

I'll go do some checking with a DVM
 

Spareparts

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So now i feel kinda dumb but not really my fault i think.
You mentioned a second switch behind the compressor.
The old compressor had one but that was smashed and was not plugged in. It was a old compressor from a wrecking yard someone put on it so i did not think a thing about it as i never saw a unused plug in that area.
I just went and looked real close and sure enough there was a plug tucked into the wire harness.
Put a jumper across the plug and the pump now turns on and off with the switch and seems to be working properly:cheers:
How important is that switch?
Photo is about 5 minutes at 1,500RPM

Ready to tackle the No dome light problem?
 

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1998_K1500_Sub

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I just went and looked real close and sure enough there was a plug tucked into the wire harness.
Put a jumper across the plug and the pump now turns on and off with the switch and seems to be working properly:cheers:
How important is that switch?

Glad I helped, if sorta by accident.

That's the high-pressure cut-out switch, different from the other high-pressure switch we discussed in this thread prior. Its purpose is to open-circuit the power to the clutch whenever the high-side pressure exceeds some value... 475psi I think, the spec's in the service manual. The other high-pressure switch operates at some modestly lower pressure, around 425psi (see manual).

Does your replacement compressor have the switch? I'm guessing "no". You can install one but you have to discharge the system to do so. If you're willing to bastardize the system you could substitute the function of the other high-pressure switch (the recirc one) for the missing one, i.e., by replacing it with a higher-pressure switch (this can be done without discharging the system) and just a bit of re-wiring. Reply if you want more discussion about it. I personally don't like bastardizing any system without good reason and in this case I would install the correct switch.

See these snippets from the service manual for their explanation of the switches' functions.
 

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1998_K1500_Sub

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Ready to tackle the No dome light problem?

Well, my understanding of the problem from reading your prior post is:

- it worked before you made changes
- you made changes
- it doesn't work now

My suggestions would be:

- review the steps you took to make the changes
- estimate which step(s) may have introduced the problem; call these "suspects"
- re-work your installation for each suspect step until the dome light works as intended


Of course there's always the outside chance that an unrelated failure caused the problem and it just happened to fail at the same time as your radio installation. But the likelihood of this coincidence is low.

If you want to describe in some detail the steps you took / changes you made, I'm willing to review them and comment.

:33:
 
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