1994 k1500 weird A/C problem

[Erin]

Ive noticed for a couple weeks now that when I’m slowing down to stop that my AC will cycle down settings (I usually run it on high/med, & it will blow less). Another thing I noticed is the med will disappear & the only settings will be low, med, & high. When I cycle through the settings ,and start speeding up, the original settings will return and it will work fine. Ive also only noticed it before the truck reaches operating speed. Does anyone have any ideas?

 

[kennythewelder]

Could be the resistor.

 

[Eveready]

I wonder if your battery is getting weak and the AC is echoing the power state as related to alternator speed. A test would be to turn on the lights against the garage door at night and let the truck idle with the brights on and the AC running. If your lights get a lot brighter and the AC runs faster to a noticeable amount when RPM goes up as you pat the accelerator then your battery may be acting more like a capacitor than a battery and you will find that out for sure when cold weather hits. Is the truck slow to start in the morning? That could be another indicator.

 

[Erin]

I wonder if your battery is getting weak and the AC is echoing the power state as related to alternator speed. A test would be to turn on the lights against the garage door at night and let the truck idle with the brights on and the AC running. If your lights get a lot brighter and the AC runs faster to a noticeable amount when RPM goes up as you pat the accelerator then your battery may be acting more like a capacitor than a battery and you will find that out for sure when cold weather hits. Is the truck slow to start in the morning? That could be another indicator.

Truck starts right up Dash gauge shows 14 volts. Nothing else is acting up as far as I can tell.

 

[Erin]

Could be the resistor.

My uncle said same thing. Next time it happens I'll be looking to see if the voltage gauge on the cluster drops.

 

[kennythewelder]

My uncle said same thing. Next time it happens I'll be looking to see if the voltage gauge on the cluster drops.

If you have never changed it, you should. It's not expensive, ($35 maybe at AutoZone) and a fairly easy job. Mine would only blow on high when I replaced mine. New resistor, and I got all my speeds back.

 

[Eveready]

I too changed my resistor and that is when I discovered that the fan bearings were shot and the fan dragged the housing noticeably at the lower speeds which of course contributed to the resistor heating up and blowing on the middle speeds. If you can get it to work at all on low speeds listen closely for a whining or scraping sound. If you hear that consider changing out the blower motor while you are at it. Full disclosure I had mine done as part of other AC work and thus have no experience on that job. From what I hear it isn't terribly expensive and not too hard to do.

It is a good idea to clean the debris out from the fan area when changing the motor. A lot of crap accumulates there since these trucks have no cabin filter. This also contributes to the resistor failure since the fan motor has to strain to pull air through. This video might be of some help

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The good news is that this is usually a one and done fix and should last if you use a good quality part.

 

[Erin]

I too changed my resistor and that is when I discovered that the fan bearings were shot and the fan dragged the housing noticeably at the lower speeds which of course contributed to the resistor heating up and blowing on the middle speeds. If you can get it to work at all on low speeds listen closely for a whining or scraping sound. If you hear that consider changing out the blower motor while you are at it. Full disclosure I had mine done as part of other AC work and thus have no experience on that job. From what I hear it isn't terribly expensive and not too hard to do.

It is a good idea to clean the debris out from the fan area when changing the motor. A lot of crap accumulates there since these trucks have no cabin filter. This also contributes to the resistor failure since the fan motor has to strain to pull air through. This video might be of some help

xc_hide_links_from_guests_guests_error_hide_media

The good news is that this is usually a one and done fix and should last if you use a good quality part.

I do have noise coming from the blower area but it's been that way for years. My blower housing is also duct taped together. I may go ahead and replace all of them it when I start digging into my problem. Thanks for the advice. I'm an amateur when it comes to this stuff.

 

[kennythewelder]

X-2 on the blower motor. Once I replaced the resistor, the blower motor started to over heat, so I did have to replace it too.

 

[Eveready]

I do have noise coming from the blower area but it's been that way for years. My blower housing is also duct taped together. I may go ahead and replace all of them it when I start digging into my problem. Thanks for the advice. I'm an amateur when it comes to this stuff.

That is very likely why the resistor is either blown or on its last legs. It would be a good time to replace some plastic. We are almost all amateurs but we have some great trucks to show for it.