Last year I changed the compressor on my blazer. I forgot to plug the front plug in (@ the clutch) it ended up grounding to one of the bolts on top of the engine. The fuse at the front blew I replaced it but the compressor will not turn on. I have checked the compressor it is good. It has the proper amount of coolent. All of the fuses are good (to the best of my knowledge). What are the odds that it could be the switch? Is there any way to test it before I spend $300 on a new one? Many thanks..

I'm getting mine looked at tomorrow if a friend of mine has the time. I'll let you know what we conclude.
I've got freon, and a working compressor as well, so it just isn't turning on.

Last year I changed the compressor on my blazer. I forgot to plug the front plug in (@ the clutch) it ended up grounding to one of the bolts on top of the engine. The fuse at the front blew I replaced it but the compressor will not turn on. I have checked the compressor it is good. It has the proper amount of coolent. All of the fuses are good (to the best of my knowledge). What are the odds that it could be the switch? Is there any way to test it before I spend $300 on a new one? Many thanks..

One possibility might be you fried a relay (inside the glove box behind a cover)

There should be three of them back there. Swap them around (one is for the fuel pump). If one is bad, eventually the truck won't run.

I really didn't understand how air conditioning works, and just found this site
http://www.familycar.com/Classroom/ac1.htm
It might not help you with the problem, but after a sleepless night it looks pretty intresting

Last year I changed the compressor on my blazer. I forgot to plug the front plug in (@ the clutch) it ended up grounding to one of the bolts on top of the engine. The fuse at the front blew I replaced it but the compressor will not turn on. I have checked the compressor it is good. It has the proper amount of coolent. All of the fuses are good (to the best of my knowledge). What are the odds that it could be the switch? Is there any way to test it before I spend $300 on a new one? Many thanks..

What year and does it have automatic air control?
A few of them you have to disconnect the battery or reset the pcm to get them going.
Does it have power to clutch cycle switch or cut out switch?
Has the system got freon in it?
MT

oh sorry about that. 98 blazer LT with climate control. It has no power to the clutch cycle switch.

oh sorry about that. 98 blazer LT with climate control. It has no power to the clutch cycle switch.

The clutch relay has two fuzes to it. IGN E and ACfuse.
Check both or all fuses and relay.
The pressure switch is a ground switch and will have no power to it.
Try jumping it or make sure the system has freon in it.
The compresser clutch relay and is controled by the VCM and air cond control module.
You need a body computer capable scanner to see what is going on or get codes.
A good scanner will tell you if the air cond controls are requesting air cond clutch to turn on.
A good service manual with the wiring is a must on repairing the system.
I can e mail you the wiring if you need it.
E mail me at crunch@troublecodes.net for wiring in a pdf on it.
But you will need a scanner to get very deep in it or to get codes.
Good luck
MT

it could still be low on r134 my bravada reads full some times when ther is not even anoth to kick the compreser on try puting some in just dont go out off the yello it is ok to be in yello. whene the compreser kicks on it will drop back to blue on the gauge

I changed the fuse under the hood. mike2004 said something about a relay behind the glove box is this true for the 98 also? Relays are cheap I can just change those out, but I don't know enough about the wiring to investigate further. I will email MT for the diagram however I don't have the scanner. Also I don't have heat but this maybe an unrelated problem. I just replaced the engine and now feel like i'm getting some of the kinks worked out with that (my recent posting about an EGR valve) and a few other things. as far as the controls go... the fan works and can be controlled be the switch also the directional switch works controlling which vent the air comes from. since the compressor doesn't turn on I don't know if that switch works. Thank you all for your help and input. Its starting to get hot as hell here in NC maybe a degree or two hotter with the worst yet to come.

it could still be low on r134 my bravada reads full some times when ther is not even anoth to kick the compreser on try puting some in just dont go out off the yello it is ok to be in yello. whene the compreser kicks on it will drop back to blue on the gauge

If that is a wal mart death kit you are using with the go or no go yellow red and green lights.
Pitch that thing in the trash can before it kills you or your air cond.
Use Manifold Gauges.
You can not safley or propley recharge or check your system without them.

http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=66773

http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=DIY-STARTER1

http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=DIYADVANCE



If it is low.

I would suspect a major leak.

MT
#1 Freon is non consumable, if it's not there then there is a leak
#2 A/C is a delicate balance between liquid/gas (low side/high side) and too much freon is just as bad as not enough
#3 If you are not prepaired to buy a set of A/C gauges, and be willing to possibly buy a vaccum pump or a/c die and replace the proper componets, then don't even waste your time.
#4 90% of the time your going to have to pull a vaccum, flush the lines and most the time replace the accumilator and the Oriface tube/expansion valve.
#5 The only easy fix is if one of the pressure switches is bad, there is no just add freon fixes.
#6 Please Please don't just add freon w/ a charging kit because you think it needs it, It doesn't work like that.
#7 These guys are a execlent source for help and if you listen to the procedures as you are told you will end up w/ some ice cold A/C, being hard headed is expensive.
http://www.autoacforum.com/


#8 And here is a link from AC kits.com to what a person needs to recharge a air conditioning.
A/C starter Kit
#9 Adding freon to a system that has a good charge can be dangerous and can cause you harm, if the pressures get to high and blow the freon can or something in the system.

I changed the fuse under the hood. mike2004 said something about a relay behind the glove box is this true for the 98 also? Relays are cheap I can just change those out, but I don't know enough about the wiring to investigate further. I will email MT for the diagram however I don't have the scanner. Also I don't have heat but this maybe an unrelated problem. I just replaced the engine and now feel like i'm getting some of the kinks worked out with that (my recent posting about an EGR valve) and a few other things. as far as the controls go... the fan works and can be controlled be the switch also the directional switch works controlling which vent the air comes from. since the compressor doesn't turn on I don't know if that switch works. Thank you all for your help and input. Its starting to get hot as hell here in NC maybe a degree or two hotter with the worst yet to come.

No glove box stuff on that one.
Check the wiring diagram.
The clutch relay has two fuse feeds to it. Make sure you have 12 volts on both. Also on the air control circuits a lot of them are ground instead of 12 volts.
And last but not least make sure you have freon in it.
Good luck and let us know how it goes.
MT

I'm going through the same problem right now. I'm going to try and work on it a little bit today. When I find the problem, I'll post what went wrong with mine.

Ok, My AC is working now. A few things that you can do-
Make sure that there is enough freon in the system (good pressure on high and low side)(you can also check to make sure that the high and low side switches are in the closed state), make sure that you turn the dial up for the blower motor (not on auto), select the other dial to blow out via the upper vents (don't select the defroster setting, that's what I kept doing and wasn't coming on), and push the ac button. If that don't work, then unplug your battery for a little while, then try again. If that don't work, then you may have forgotten to plug something back in.

EDIT - I spoke too soon, the AC doesn't work again.

Ok, My AC is working now. A few things that you can do-
Make sure that there is enough freon in the system (good pressure on high and low side)(you can also check to make sure that the high and low side switches are in the closed state), make sure that you turn the dial up for the blower motor (not on auto), select the other dial to blow out via the upper vents (don't select the defroster setting, that's what I kept doing and wasn't coming on), and push the ac button. If that don't work, then unplug your battery for a little while, then try again. If that don't work, then you may have forgotten to plug something back in.

EDIT - I spoke too soon, the AC doesn't work again.

Go easy on that battery disconnect you can do more harm that good with that.
Go to post no 7 if you auto control you will need a body comp capable scanner to see what is going on.
Mt

Just had similar on/off problem and it was a connector behind the compressor and had to tighten the pins inside. Also had a pressure switch on the accumulator with loose connector before so if you have the AC and Blazer on shake the connectors and if you are lucky you found it.

We just had a GM product charged up today at the car lot, and it apeared that one of the 2 switches wasn't working.

I had the idea of disconecting the battery, for a 1/2 hour and seeing if re-seting the computer helped.

It works now, so it must have