Air Conditioning Fuse Keeps Blowing

[Craig]

Just replaced the compressor and pressure switch on a 94 Yukon. The A/C runs well for a short time but blows a fuse.

Any ideas on what the issue may be?

 

[Tavi]

A few questions.

1. Did the fuse ever blow prior to the parts being replaced?

2. How long is a while? Fuses are designed to run at slightly elevated levels for a short period before burning out.

I would use a multimeter in place of the fuse and check the amperage flow with the system on. This might give you an idea of when and where the spike or gradual increase is according. My guess is a faulty compressor clutch. I would bet you see a spike when the clutch kicks in. But I am not an AC guy, so I could be very wrong.

 

[Urambo Tauro]

Be careful using a multimeter to check amperage without fuse protection. It could blow the meter's internal fuse (if equipped). But you already know that it's pulling too many amps, so you might want to just skip that part and start hunting for a short instead. Unplug the clutch coil and check power supply at the plug. There should also be a resistance check for the coil that you can perform, but I'm not sure what the specs are for that. Maybe someone else can chime in...

 

[Craig]

Okay so I'll provide some background here.

I took my 94 Yukon in for warranty work. Apparently the compressor was leaking and needed to be replaced. Prior, it worked fine for over two years (3 year warranty), it just had a slow leak.

So I take it into the shop and they replace the compressor and the high pressure A/C switch after they told me it was nonfunctional. After running it, the vehicle started to blow the a/c fuse.

They diagnosed the issue as a non-unwarrantable wiring issue so I agreed to have the "clamping diode" replaced and to have the wiring harness fixed. I was told this would be all I need to get it back on the road. Usually, I like to do things myself but the shop had it all apart and had already charged for a full diagnostics to check the A/C system because it wasn't coming from one of the parts they had previously replaced so I bite the bullet and paid for it to be fixed.

Now they called me today and apparently the low pressure switch has melted and I'm asked to replace that.

Although these are minor wiring issues, it's a rather expensive shop quoting me about $700 CAD ($160 diagnostics, $100 clamping diode, $140 pressure switch, $30 connector $200+ labor) after just on these non-major issues so far on what I expected to be a no-charge warranty item. I'm a bit stressed about the situation.

I'm thinking the new compressor may have caused these issues as none were present before this warranty work.

A few questions.

1. Did the fuse ever blow prior to the parts being replaced?

2. How long is a while? Fuses are designed to run at slightly elevated levels for a short period before burning out.

I would use a multimeter in place of the fuse and check the amperage flow with the system on. This might give you an idea of when and where the spike or gradual increase is according. My guess is a faulty compressor clutch. I would bet you see a spike when the clutch kicks in. But I am not an AC guy, so I could be very wrong.

1. No. It worked find.

2. I was told a few minutes.

 

[Tavi]

I find it hard to believe your system magically just started showing signs of harness failure after they replace parts. They screwed something up and are trying to charge you for it so it doesn’t come out of pocket.

 

[Schurkey]

"I" would want to know what that fuse powers. (Everything it powers, if it's powering more than one thing.)

Wild guess: It supplies power to run the electromagnetic clutch coil on the AC compressor.

Find out how many amps the compressor clutch coil is drawing. If it's excessive, they installed a defective part and owe you a COMPLETE REFUND and an APOLOGY.





Another wild guess: That diode should have been $2, not $100. The prices on the other parts seem suspicious as well. I think the shop is trying to recover the "warranty" costs by overcharging for everything else.

 

[Craig]

Just an update. I pulled the truck from the shop after they gave me a $300-$325 quote for the low pressure switch and connector which is a 5 minute job I did myself with A/C Delco Parts for $80.

So I paid for the diagnostics, diode (s1473) and labor which came to a little over $300 after a lot of talking.

I took it to a family friend and he tested the compressor and it's not reading excessively.

Since none of these issues were preexisting, my best guess is that this damage occurred sometime while the warranty work was done. But I have no way of proving it and no big reason to complain as the shop is honoring a second hand, 2+ year old warranty.

I can't thoroughly test it until Spring but it seems to be working alright now.