2002 Blazer 4D, 4WD, 4.3L, AC
Haynes Book doesn't have any detail on AC circuit. Compressor will not engage. I did jumper the clutch and it works. I need to know what must be satisfied in order for the clutch to engage. 30 amp fuse is OK and I switched the horn and AC relays, and they appear to be OK. I saw a "thumbnail" picture of a circuit in another thread, but it would not enlarge when I clicked on it.

 

This is supposed to be 1998. Maybe it will do.

 

Have you tested for 12v at the 30amp fuse? I do have a wiring diagram Not sure if it is the correct one. But you can always try and chase the problem with voltmeter.

 

Just what I need (I think). Two different versions, but I will see if either is correct. I'm busy this morning, but will proceed this afternoon. The 30A fuse is good, but I did not check for voltage at that location. Will do. Maybe it is just low on 134 Freon (if that is still what you call it). I have a can, but did not want to add until I knew if that was the cause. Somewhere, I read that the pressure switch must be satisfied to allow the clutch to engage. I will try to check this also. Thanks again! Now it is my turn.

 

Clutch will not engage if the pressure is low due to low R134a. Here is the link of when I rebuilt my A/C last summer. Lots of good info from the members here especially Captain Hook:

https://blazerforum.com/forum/2nd-ge...pressor-90114/

 

Lesmeyer's schematic is the most accurate with my system (I think). 10a A/C fuse, 10a IGN E fuse, 20a HVAC fuse are all good with 12vdc on both sides with key ON. The A/C Compressor Clutch Relay is side to side with the Horn Relay with the same part number. I exchanged these with no change. The horn works both positions, so I assume the relay is OK. Not sure now what actuates this relay to operate the clutch. The HVAC ***** and speed controls all work on the instrument panel. Suspecting the Pressure Sensor, but don't know at this point how to check it or where exactly it is found. I have a gauge set. Maybe I should hook up and see what the LOW and HIGH pressures are "at rest".

 

Can't find the older Thread, but, CaptainHook made some troubleshooting suggestions that I have been trying to follow. Here are the results:
1. The A/C relay has 4 wires: pink, black, white, and dark blue.I could not determine the colors under the receptacle in the fuseblock but I get these results with the key ON and A/C mode switch ON.
Pink and White both show 12vdc (#86 & 87 on the relay blades)
Black shows 10ohms to ground (#85 on the relay blade)
Dark Blue shows 7ohms to ground and when 12vdc is applied,the compressor clutch is actuated. (#30 on the relay blade)
2. The Clutch Cycling switch on the Accumulator is Open which means less than 22psi.
3. The High Pressure Cutout on the backside of the Compressor is closed which means less than375psi. The front connection shows 12vdc and No ground. I finally acceptedthe fact that the Ground wire is what completes the circuit instead of the12vdc wire.
4. I borrowed Manifold Gauges from AutoZone and the pressure at High and Low ports are both 0psi (zero).

My conclusion is that there is no R134, or so little that it will not start. Is this right?
Can I kick start it? Or do I need to take it to an A/C shop and have it leak tested and recharged? Or is there another solution?

 

Should have the desiccant replaced and system evacuated / tested to ensure system will hold vacuum (no big leaks) before freon is added. Others might just add freon (compressor will engage when you start to charge) and see what it does but that's not how an environmentally responsible person would act. Freon 134a is still not good for environment if it leaks back out. Use your best judgement.

 

You can add R134a with UV dye to find any leaks then have the R134a properly evacuated before you open up the system. As Les said, never just dump the R134a into the air.