You guys may have heard about this before, but if not, I'll tell you now. Have you ever wanted hot air to just blow on your windshield, but don't want the drag of the a/c compressor?. Sometimes, major condensation is not an issue, just a little fog on the windshield, but you can't turn on defrost without the a/c automatically kicking on. I figgered there must be an electrical switch in the heat-a/c cluster that closes when in the full defrost mode and that the switch could most likely be unplugged by accessing the back of the cluster. Doggone if I wasn't right. I just took off the center cluster finish panel (pull the knobs off the heat and a/c and fan control knobs and levers. then gently pry off the trim piece. there are 2 screws there and 1 more down by the ashtray. Then if you pop off the lower center cover, the center cluster finish panel just pops off.) Then you can reach in behind the right side of the cluster and disconnect the little wire harness and your good to go. You can still have defrost with the a/c comp by simply pressing the a/c button when you want it. (some of you may not even know or care but the a/c pump sucks moisture out of the air and is not always necessary if you dont have a lot of moisture in the air to begin with.) This mod may be slightly different on some years and models but the controls should be somewhat similar. Sorry I don't have pictures and all that but I dont have the camera and anyway I'm not much of a computer geek. Hope I helped

 

Okay, tell me this isn't the same on the 2nd gen trucks..... I drained my AC pump/lines for my OBA conversion and have been at a standstill for a month and a half. I really don't want to have a fried pump when I actually convert. From what I have *seen* on my truck... the AC is a seperate button from the rest of the controls. The defrost isn't a button but is on a slide switch. I've never felt the drain of power like I did when the AC was on. And the last time I had my climate controls pulled out, I didn't notice any wires coming from the climate control unit that would indicate that it was connected to the AC pump.

 

I think you are right on that. It does run the A/C when you defrost on my Tacoma (98)...but it does not run it on my wife's 4Runner (94). I would assume other vehicles 95 or earlier would be the same.

Jim

 

Cool find!

 

Sorry I didn't specify my vehicle, it's a 99 taco trd 3.4l . The climate controls (as well as almost every other dash control) is the same as my wife 99 camry. I've also noticed the same redundant a/c-defrost compressor action on other cars that I can't recall at the moment. The second gen trucks may not be the same. I had an 82 toyota 4x4 (that I wish I still had) and I dont think switching the duct to defrost activated the compressor pump in that rig.

 

Ya, in deforst mode on 2nd Gen's (and corresponding gen trucks), the AC does not come on automatically.

But, in 3rd Gen's (and apparently corresponding gen trucks), the AC does come on in defrost mode. (I hope that all came out right)

 

ON 2nd gens the a/c is a seperate function from the defrost. The a/c comes on the same time as the defrost on newer models because without it the windows will not clear very well with just the defroster on especially on cool rainy days. Your hot breath is what causes the windows to fog up so you need cold air to clear them. That has been my experience. They do this because the majority of people are either too lasy or too dumb to press the a/c button when their windows are fogged up.

 

The A/C doesn't run cause you need cold air to remove fog, it runs because the condensor removes the moisture from the air.

 

It's good exercise for the compressor too in the winter months. Having it sit idle 9 moths a year =

 

Your right, sorry for wrong info.:pat:

 

Not sure if this is true with all vehicles but in my previous car, there's a sequence of buttons pressed that will give you control over the a/c. No need to get behind the dash.

 

Post from the dead, but thank you for this info. Took me about five minutes to disconnect the connector after reading your post.

I've just hated having the a/c run in the defrost position as I use the defrost position often and use it mostly as a source of fresh air. Yes, I'm smart enough to turn on the a/c when the windows get foggy.

 

I don't think mine runs un my 98 4runner. Does the light light up when it comes on. There are some other reasons too i don't think it works that way either. I had the AC compressor lock up and took a few months before i replaced it and I never heard the belt squeal or anything with the defrost on. It would scream like a sun of a bitch though if I hit the AC button.

 

My 96 Taco has a separate system, I also run mine on bi-level most of the time for heat from the defrost ports and down below from the heater ports. On "wet" days the windows will fog up unless I hit the A/C button and then they clear up pretty quick. I also agree that it's a must to turn on the A/C pump at least once a month but once a week is best to keep them from freezing up.