Electrical mod question for Hyundaitech

I'm not sure if you'll even want to answer this, but here goes.
I really dislike the fact that the A/C in my '04 Elantra is coupled to the defroster so that the they always come on together. I've heard a
rumor that this is a new federally mandated setup, but frankly, it really sucks if you live in a cold environment and need maximum heat to clear snow and ice from the windshield. On '03 and older cars, it's a simple matter of snipping one signal wire to decouple them, but still be able to turn on the A/C manually with the defroster if you want to.
Unfortunately, he '04 has a different control module that's more difficult to decipher. I've examined the wiring diagrams, but it's hard to relate them to the components. I'm on the verge of opening the control module in the dash to see if I can find where the signal from the mode selector switch connects to the the A/C signal output, so I can sever the connection. Any ideas?
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The climate control head communicates a/c compressor request directly to the PCM, and they don't specify the nature of the signal. I'd be tempted to put a switch inside the vehicle in-line between the a/c relay and the compressor. That way, you'd be able to reenergize the compressor when you wished.
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hyundaitech wrote:

Thanks for the pointers.
Functionally, that's what I want to do. I'm thinking that I may be able to use the existing switch by carefully re-routing the wiring. Essentially, I would have the a/c signal on all the time between the control head and PCM (bypassing the existing switch), but put the switch in the signal line to the relay or between the relay and compressor as you suggest (if it will handle the current load). That would maintain the stock appearance and intuitive functionality. Thoughts?
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| I'm not sure if you'll even want to answer this, but here goes. | | I really dislike the fact that the A/C in my '04 Elantra is coupled to | the defroster so that the they always come on together. I've heard a | rumor that this is a new federally mandated setup, but frankly, it | really sucks if you live in a cold environment and need maximum heat to | clear snow and ice from the windshield. On '03 and older cars, it's a | simple matter of snipping one signal wire to decouple them, but still be | able to turn on the A/C manually with the defroster if you want to.
I agree with you. This was one on the list of engineering stupidities of my late Ford Aerostar, which has met its just reward after passing through purgatory. This design sticks in my craw (and I don't even know what a "craw" is). And I don't even live in a cold climate. My 2000 Sonata's heat comes up nice and quick, but if I lived where it's cold, I'd want a whole lot quicker.
The other thing that gets me is that carmakers have been making "always-on" heater cores, with the output controlled only by a big air flap. In my experience, these tend to leak hot air into the interior on a hot day. I'm not certain that my Sonata is set up this way -- I haven't owned the car long enough to investigate. It's an old practice, though: it was a "feature" of my 66 Plymouth. I can't understand why they didn't use the old-time idea of just putting a water valve in the hot water line. These flap air deflectors leak in two ways, often both at once: - They radiate from the heater housing, which is usually black to help transmit the heat. - The flaps often don't seal very well, either due to internal leakage past the flap, or from wear in the vacuum activators, or even perhaps a little vacuum leak in the tubing or controls. The result is sometimes hot air blown on your face whenever you want heat on your toes.
So, I've often wondered about the practicality of just putting a water valve in one of the heater hoses to shut off the heat totally in the summer. Or, is there some reason why the engine or emissions will be harmed if the coolant isn't circulated through the heater at all thimes?
Richard
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My experience is that the problems with the water valves tend to be worse than the side-effects of an always on heater core. The water valves bind, or worse, leak sometimes. Having experienced it both ways in my cars, I'll take the always on heater core.
There's actually a good reason the automakers turn on the a/c for defrost. It dehumidifies the air and defogs the windows much more quickly. But, I can also see the desire to have it not energized if you're still getting cold air.
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| My experience is that the problems with the water valves tend to be worse | than the side-effects of an always on heater core. The water valves bind, | or worse, leak sometimes. Having experienced it both ways in my cars, I'll | take the always on heater core. | | There's actually a good reason the automakers turn on the a/c for defrost. | It dehumidifies the air and defogs the windows much more quickly. But, I | can also see the desire to have it not energized if you're still getting | cold air. | Thanks. I sit corrected. I wonder if the valve problems may have something to do with mineral content in the water -- I've never experienced this problem in my life, but I've never lived where the water was very hard. I understand about the defrost a/c. There's a hidden comfort advantage that I've found with this: running the defroster in the summer is a nice way to get diffused cold air from the air conditioner, rather than the usual blast in the face. Try it, you'll like it.
Richard
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hyundaitech wrote:

I've had leaky heater valves and they're not fun to deal with.

Having dry air can be critical to de-FOGGING the INSIDE of the windshield. Where I have an issue is when I'm trying to de-FROST the OUTSIDE of the windshield. The reduced air temp from having the A/C compressor running reduces the efficiency of the defogger/defroster in clearing snow and ice. I had a problem with this on one particularly nasty trip this winter and I'm going to do something about it before it gets me killed.
BTW, I understand that Canadian market Hyundais do not have the a/c and defroster coupled permanently. When you turn on the defroster, the a/c turns on (and the switch lights up), but you can manually turn it off. That's a good solution and what we should have here, IMO. Unfortunately, it appears that the parts are not interchangeable.
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There is a catch, also. That way, water taken from the air is trapped on the evaporator, and quickly released back into air stream if you turn off a/c. So if you defrost with a/c, you have to keep it on. And I don't like to drive around in winter time with a/c running. Or better said, I don't like to use it at all untill the heat is unbearable.
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On Fri, 25 Mar 2005 14:47:32 GMT, Brian Nystrom

=================== In my 'old' cars, the a/c systems had ambient temp sensors (about 36-38 degrees F.) that killed the power to the a/c compressor clutch when the temp was low. Doesn't do the compressor any good to pump into a frozen system. Have you actually looked at the compressor to see if it runs? Or are you just looking at the dash light?
I'd check on my Santa Fe, but I live in Florida and ... =;-)
    S25
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