# Checking if an A/C fuse is good or bad?



## fin29 (Jun 4, 2003)

2003 Isuzu Ascender--identical to GMC Envoy

The A/C isn't working in my vehicle--the fan comes on, but it doesn't blow cold. I found the related fuses, and one of them is your basic transparent fuse that I can see is good. The other fuse is an apx. 1x1" opaque gray fuse and I can't tell whether it's good or not just by looking. Is there a way to tell if a fuse is still good--a volt meter or something similar? I want to make sure it's not something as simple as that before I bring it to the dealer for service.


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## ninny (Dec 12, 2005)

If you've got a volt meter, it probably also has the ability to check ohms, that's resistance or continuity. Put the meter on the ohms scale and check across the fuse and you should get a reading if the fuse is good or some meters have an audible tone that sounds if the fuse is good. To make sure you have the meter on the right scale and operating correctly, touch the two leads of the meter together and you should get a reading. Other than that just replace the fuse, they're not that expensive. Or go to an auto parts store and they can check the fuse for you.

.


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## Cabin Fever (May 10, 2002)

If you don't have a volt/ohm meter, bypass the fuse by sticking the two ends of an insulated wire into the two sockets where the fuse plugs into. Start the AC. If the AC works, you can assume the fuse is bad.


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## DrippingSprings (Sep 22, 2004)

check to see iif the ac clutch is cycling on and off. If it isnt you pressure cycling switch could be defective. If you think it may be low on coolant it will keep the clutch from engaging as well. 

turn the vehicle on and raise the hood. locate the ac compressor and have someone turn the ac on their should be an audible clck if not you have no clutch engagement and it will blow air but not cold. 

the cycling switch looks like this









it costs 12.99 part number Santech MT0968 and it simply screws in. Anyone can do it.


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## farminghandyman (Mar 4, 2005)

the pulley will turn all the time on the AC compressor but the center of it will turn on and off, if it is cycling,


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## Junkmanme (Dec 16, 2006)

The pulley mentioned by "farminghandyman" is an electric-powered clutch, activated by the cycling switch pictured by "DrippingSprings".

The answers you received should solve your delimma. (sp?)

I HATE to take a vehicle to a shop.....PARTICULARLY the high-priced NEW AUTO DEALERS! (Last I heard, the "flat-rate" here was $65.00/hour (that's about 5 years ago) and the mechanics were still making the same money they made when "flat-rate" was $50.00/hour.)


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## agmantoo (May 23, 2003)

If the vehicle is low on freon it will behave as you described.


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## Herb (Jun 25, 2006)

+1 on the system being low on refrigerant. Bypassing the fuse with a piece of wire is a bad idea. If the fuse is bad, something made it go bad.
Use a meter to check if the fuse is good. If you don't have a meter, most auto parts stores will check it for you.


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## fin29 (Jun 4, 2003)

To check if the relay was bad, I grabbed another one that I knew worked and stuck it in the A/C slot--no click to engage the clutch--but I replaced it anyway since I was in the parking lot of NAPA anyway. I'm trying to find the switch you mentioned locally. Thanks for the help...I'm going to try everything before I pay a couple hundred dollars to get the system recharged.


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## fin29 (Jun 4, 2003)

This is the clutch switch I found on line, but I can't find a picture to verify if it's the part DS was referring to: 
ACDELCO Part # 1550156 {#89040362}
Category: A/C Clutch Switch

I found it at http://www.rockauto.com/catalog/catalog.php
Can anyone verify that this is the part I need?


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## agmantoo (May 23, 2003)

You need to find a knowledgeable person that will be able to determine if the low pressure cutout switch is open due to low freon prior to starting throwing out money for parts that you do not know are good or bad. The all too frequent problem with non functioning AC is low freon.


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## fin29 (Jun 4, 2003)

I don't consider $20 to be throwing anything away, considering the cost involved with taking the car to the dealership (at God knows how much per hour), and especially considering the fact that my research today indicates that the A/C clutch is inherently flawed in 2003-2005 Ascenders, and it causes the problem I'm having. The compressor isn't cycling on or off, which would be an indication that the clutch (or something) is bad before it would suggest the freon's gone. Course, it could be both, but I'll take a $20 chance and change it out myself before I'll pay a GM tech $100 to do the same thing, since the TSB regarding Ascender A/Cs specifically addresses the clutch as the primary culprit with this problem.

I don't disagree that I may be over my head, but I can definitely handle changing out the switch. I just need someone here to confirm that the part I listed is what I need, since I can't find a picture of the part anywhere.


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## DrippingSprings (Sep 22, 2004)

There is no need to pay that much to have coolant added to your vehicle. You can buy the small blue hose with the quick connect for about 8 dollars and the coolant for 6 or so per can. Many is the day Ive walked out in the parking lot and pointed out the way to do it in less than a minute to my customers. Its an r134 system. You can add to it yourself. The only time you need any special tools etc etc is if you are emptying the system etc and need a vac to pull it out. Youre just adding is all.

Yes thats a clutch cycling switch. 

Here is a link to how to do it yourself complete with pictures. Note you do NOT have to have manifold gauges etc. 

http://www.sadik.net/nissan/howto/ac_r134.htm


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## agmantoo (May 23, 2003)

Since you are intent on buying something may I suggest a volt ohm meter and learn how to use it. In so doing you will avoid blindly changing components that are not defective and avoid a lot of frustration. The VOM is real handy for other things around the place also. The VOM can verify the fuse is OK, check the relay you replaced, check the clutch switch, check the windings in the clutch itself and will tell you if the low pressure cut out switch is open and verify the wiring has continuity.


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## Ross (May 9, 2002)

I've use the sysytem DS describes and it works very well. You should have a meter too, they can be had for under $10 and will get the job done.


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## DrippingSprings (Sep 22, 2004)

yes a Digital VM is worth its weight in gold. You can test just about every component in your engine management system. Most without removing from the vehicle.


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## fin29 (Jun 4, 2003)

Thanks for all the advice. I'll take it and let you know what happens.


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