on the quest to get back the old gas mileage(240 out of a tank) on my gf 99 3.2 auto amigo, i think i might have found it.
When i turn on the heater, i can hear the a/c kicking on. It also affects the rpms at idle. Is this normal? ive heard that it helps dry the air for the defroster. Can anyone confirm this?

kevan

Yes the AC compressor will come on with the defroster, although there is usually a thermostat that disengages this feature below a certain ambient temp...no need to de-humidify at 10 degrees or whatever.

It shouldn't come on with just the heater, though.

Here's how mine works:
Always seems to stay on for the "defroster only" setting.
Cycles on/off for the "defroster and lower" setting
Never on the rest of the time (unless of course the AC is on).

I wish I could find a way to turn the AC off completely for the "defrost and lower" setting. I use that setting the most here in Oregon, and I'd prefer not to have the AC come on at all. If I need to I can switch to the "defrost only" and have the AC do its job there. The AC is really effective at removing moisture from the window, but I don't like having to run the AC just to have a little defrost like I normally need.

Should be able to pull the plug on the compressor that engages the clutch. That will just let the clutch freewheel. Be sure to cap off the plugs to be sure no dirt or moisture gets in there.

Dan

I agree...my old 88 Pathfinder had a separate button for AC, and I could engage it at my choice when in defrost mode. Sometimes you need the dry air, but there are plenty of times around here when AC to the windshield isn't needed, just warm air.

First Gen Rodeos have the same set up (no interlock between AC and defroster).

Her 99 amigo has a seperate ac button. It turns on if it is on or off. Also, the ac turns on if its in the defrost position or not. What would be the best way of fixing or disconnecting this? Is there are fuse for this?
Im gonna do a better test today and tell ya then

oh yeah, ive replaced, plugs (champion), filter (fuel and air) all oils, cleaned the heck out of it with sea foam, cleaned hoses, egr valve,

kevan

anyone have the slightest idea? <img src="/forums/images/graemlins/scared.gif" alt="" />

240/16= 15 mpg (on stock tires) 17.6 but 1.6 is reserve <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/confused.gif" alt="" /> <img src="/forums/images/graemlins/zombie.gif" alt="" />

So those figures are stock? what about with the larger tires, where are you at there? I know I get just about 15mpg on my tank with 33's. I do have to make the compensation though, or it looks much worse.

I get around 255-270 on the tripometer for a tank, at about 19gals. That would equate to only 14.2mpg, but when in reality, with the larger tires I am getting 265-290miles to the tank(about a 7% increase although it might be more around 9%) That gives me 14.2-15.2mpg(during the winter)

You will always get worse mileage in the winter, it is just a fact. The gas is processed differently so mileage drops with it. Just keep that in mind.

I set up a switch to kill the A/C and also one for the ABS by taking apart the underhood fuse box in my VX. I love this switch and use it all the time. My compressor only runs a fraction of the time it used to in the defrost mode. A/C in the defrost mode is only needed to clear inside fogging. Any other time it's robs HP, fuel, money, and it's unnecessary wear and tear on the A/C system. Lots of people do this with all kinds of vehicles. The easiest way to stop the auto A/C in defrost mode is to get into the dash and destroy the contact points that make the A/C clutch engage in defrost. If you know what wire sends that signal, just cut it. You will still have manual A/C in defrost just like any other mode. Here's how I did mine- [color:"red"]A/C and ABS Kill Switches[/color]

[color:"red"]My '99 Isuzu Vehicross[/color]

Mark Griffin

I swear when we first bought the truck it would go over 300 miles on one tank, now it gets 240. These are stock numbers, with stock tires and rims. It didnt make that much of a diff with my tires on. 32X11.50
how lond did it take you to make those switches?

kevan