Hey, well first let me tell you that I have searched all over the forum and I found a lot of valuable info that helped me trouble shoot, but now I have to get in to specifics.

98' Blazer had it for 4 years
Earlier this summer I finally recharged my A/C unit after not having A/C for the last 3 years It would just cycle on and off. I never stressed it cause I was broke for the first few years and just learned to deal with the heat. Now I been working on everything myself and finally got a round to A/C I know my truck very well inside and out. Well after Recharging my A/C after 3 years everything was working well, unitil I was sitting in drive thru for a long time, real hot day then my temp gauge shot over to the red. And ever since then when I come to a red light or idle the temp gauge starts to move over to the red until I take off.
What I have done:
new T stat, flush and fill 3x, rad cap, fan belt, burped it several times, flushed heater core it was basically new only 2 yrs old,
I bought a new fan clutch cause the fan wasnt giving much resistance when turning it. And with the A/C on It doesnt change speed it is always on never goes amy faster. I havent put it on yet cause the original fan clutch is still on there and will not come off, so i am going to let a mechanic do it for me. I dont want to round of the nut.
I just want to know what else could it be? Thanks

 

Seeing as the engine cools off when you get air flowing through the grille and rad, I believe your trouble is the fan, maybe the clutch not engaging like you've already thought about... Wait and see what happens after getting the new clutch installed. Something tells me the fan's not spinning.

 

im hoping it is the fan. Cause its not going an faster with the A/C running so I'm going to get it put on wed and tell you guys about it. Thanks

 

You can check the clutch fairly easily. Once the engine is up to operating temperature and you shut the engine off, the fan should have a good deal of resistance to it if you were to attempt to spin it. There should be a noticeable difference when compared to a cold engine.

It is some what rare for a clutch to fail in this manner though not impossible. Fan clutches that i have had fail have always failed engaged which causes a roaring sound.

 

Have you checked to make sure both the upper and lower fan shrouds are in place? Also, getting all the bugs and leaves out of the fins of the a/c condensor and radiator?

 

Swartlkk: I never tried turning it after letting it reach temp. I will try that
AJBert: I hosed the radiator down in the front and got most of the leaves and bugs out I will go back and do a more thorough job.

 

Ok changed my fan clutch yesterday, riding it today and still overheats when I idle also cleaned out the leaves and bugs from my radiator. I dont know whats going on. I hope I dont need a new compressor because like I said before It had never been charged for 3 years.

 

My 2001 is doing the same thing but if I turn the a/c off it will not overheat at all, no matter how long I idle.

 

The AC has it's own set of high and low pressure switches that kick the compressor in and out as required; the fan clutch should engage when the AC is on. If it doesn't, check the switch. Can't remember the name of the switch, but the fan clutch may be totally fine it's just not being prompted to turn on. Does the fan ever engage? If the fan works, remove the grille and blow the radiator and condenser out. Remember to blow things back out the way that they entered!! This means blowing from the engine side of the radiator towards the front of the car; you may have to remove it to get it all the way clean. Finally, a failing water pump will exhibit the exact same symptoms. Slow to circulate at idle, then speeds up the circulation when the revs come up. I would start by:
1. Check to see if the fan works. If your temp is in the red, the fan should be on. If it works, see #2
2. Blow out the radiator/condenser. It's free and if it hasn't been done, it needs it anyway.
3. Buy a water pump; not free, but shouldn't be greatly expensive. I am willing to bet that this is the cause of your problem.

 

The fan just keeps at a constant speed never goes any faster and it is always on as soon as I start it up. Im going to check on those switches. The water pump will be the last thing I check hopefully its the switch.