Hi all,

Just got my new baby: an 04 Silverstone and I'm enjoying the heck out of it! I considered the GPW, but in the end, the light tan interior just wasn't for me.

Anyway, I've been having some issues with the AC. The AC temp fluctuates pretty often. I'll have the fan speed at 1 and the temp right in the middle and everything will be fine, then all of a sudden, the air gets warmer; forcing me to lower the temp dial. Again, everything fine, then, all of a sudden the air gets really cold; forcing me to raise the temp dial. Don't know what's going on. It's very frustrating!

I thought, perhaps because its a convertible, the outside heat might come in easier, but I don't know, I've never owned a convertible before. This doesn't seem like it should be happening.

Any help would be great. Thanks!!

 

All A/C systems fluctuate as the compressor cycles on and off. If you are used to "Climate controls" (I love that - can you dial up Siberian Tundra?) that run all the time, it may be that you are just noticing it more.

If you have the temp anywhere than all the way to the left, then the HVAC system is running coolant through the core, and will exchange some heat into the car when the compressor cycles off.

I believe this is your problem - you created it and can stop it.

BTW, A/C runs most efficiently when higher fan speeds are used.

 

Thanks!

Dunno,

I've never experienced this in other "modern" cars. Even my 88 Landcruiser doesn't fluctuate thaaat much. I mean it feels as if the AC stops working altogether sometimes.

Now that you mention it though, the fluctuations do coincide with the compressor coming on and off.
Its frustrating. So you say that if I have the fan speed higher it wouldn't happen as much? So just point the vents elsewhere.

Thanks again for the info.

 

I believe you missed the point - having the temp gauge in the middle is actually a heat position. Move it all the way to the left (counter-clockwise) and your problems should be over. Got it?

 

I'll give it a shot.

Thanks!

 

Do you find that the heat goes up when you take a sharp turn, like a left turn in particular? When you have some heat dialed in, turning seems to make the heater core hotter. I find this in winter when the heater is going and the fan is on 1 or 2. When I make a sharp left turn, the heat coming out of the registers get a lot warmer. I have no logical reason why (yet).

 

Well,

Haven't gone through a winter yet with the car so couldn't tell ya :-) It just doesn't seem logical that if the temp dial is "not" on all the way to the left (cold) heat will come out. The temp dial is specifically for that, for dialing in the temp. If I leave it on 3/4 cold, it should stay at 3/4 cold (at least more or less); thats what its there for. I don't agree that if I have it at 3/4 cold, that its automatically in a heat cycle. Right now, its either arctic tundra or I have to turn it off. Its just really annoying. Llike I mentioned above, I have an 88 Landcruiser that has a somewhat strong AC. The fan speed is always at 1 and its still to cold. So what do I do, I raise the temp a bit. It works. The air coming out of the vent is slightly less cold and it stays like that until I change it. If I do this in the S it will work for about half a minute then the air will get too warm, forcing me to lower the temp. Then it will get too cold, forcing me to raise the temp again.

I drove it last night with the temp all the way cold at fan speed 1 and I had to move the vents away from me. I was freezing!

Anyway Brrrrr!!

 

I've found that in this car more than others that I have owned the temperature fluctuates more with speed, or engine RPM's. So if you are in stop and go traffic you might notice a lot more fluctuation in the air temp. I constantly have to adjust the setting 1 notch up and down as well. I need an inbetween setting!

 

You have to understand how your HVAC works, in particular, that heat knob. When you turn that knob, you are changing the position of a valve that lets more or less engine coolant into your heater core. Although it is possible that you have a poorly functioning valve, the following is a better explanation:
If your heater knob is even the slightest bit off full COLD, you are letting some water flow through your heater core. After a cold start, of course you will get cold water. As your engine heats up, so does the water going to the heater core. When you rev your engine, the water pump pushes even more water through the core and if it has gotten up to running temp, the core will put out more heat. If you make a sharp turn, the water can tend to flow even easier (especially a left turn) into the heater core, making it put out more heat.
That knob is just an approximate device that "gates" the water flow. Other things (as I've already explained) can adjust that water flow as well.

 

I think what you're experiencing is something that Road Rage touched on - the ac compressor cycling on and off. When you're AC is on 2 things are happening: 1. the fan is going, moving the air along and 2. the AC compressor is operating which is cooling the air. With any AC system the AC compressor cycles on and off (it's usually on, but can shut off for a minute or so and then turn back on) When it's off the air isn't being cooled, so basically all that's happening is the fan is moving air. Some people have noted that in the s2000 the ac compressor seems to cycle on/off more frequently than in other vehicles. This may, in fact be the case, but it's also possible that because the cabin is so small in the s2000 that when the compressor turns off momentarily you can feel the temp difference right away.

It sounds like what's happening in your case is that you've got the temp setting somewhere in the middle. The compressor shuts off and the result is warmer-than-desired air blowing out. You turn the dial cooler to compensate, and after a short amount of time the compressor kicks back on and starts cooling again. The result is much colder air than what you originally wanted so you've got to change the temp dial again.

I've seen some discussion here in the past, in fact it's been a long time since it's been brought up, about what causes the ac compressor to cycle on/off. I don't know if a clear answer was ever reached.

Anyway, hope that helps.