Dear Tom and Ray:

Here's one for you! Ever since my brother-in-law adjusted the idle speed on my '85 Mazda 626, it just hasn't been the same. Now when Iturn on the air conditioning, the idle revs up and down, up and down, constantly. When I have the air conditioning off, it revs every time I turn the steering wheel at a stop. What can I do? It's dangerous! - Adrian

RAY: First of all, Adrian, we're sending a copy of your letter to the Society for the Defense of In-laws. Everybody wants to blame his or her in-laws for something, and we've had enough of it! Your poor brother-in-law had nothing to do with your erratic idle.

TOM: He probably DID clean out all the change from under your seats and spill cream soda all over your carpet, but he didn't mess up the idle.

RAY: Your car has what's called an "idle-up diaphragm." When you use the air conditioner or power steering, you impose a heavy load on the engine. To keep the engine from stalling, a vacuum is automatically sent to the idle-up diaphragm to increase the idle speed. When the diaphragm is sucked in by the vacuum, it pulls a rod attached to the throttle, which ups the idle speed.

TOM: Your idle-up diaphragm probably has a small hole in it. So the vacuum can suck it in but can't hold it in place. And as the diaphragm slips back and forth, the idle speed moves with it.

RAY: You need a new idle-up diaphragm. See if you can get your brother-in-law to pay for it. Tell him you wrote to us and we said the whole thing is his fault.

Dear Tom and Ray:

My husband and I have a 1990 Buick. The problem is that he simply refuses to use the air conditioner. We have had new cars for the past several years, and he always says that using the air conditioning in city driving will cause the car to overheat and vapor lock. We have had temperatures approaching 100 this summer, and yet he insists we drive with the windows open, blowing hot air into the car and completely destroying my hairdo. I asked him if maybe cars these days are made so one could use the air conditioning without a problem. He says no. Please comment on this in your column. - Betty

RAY: Well, Betty, we sent your family stationery out to be carbon-dated, and the results indicate that you and your husband have been around for a while. Right?

TOM: Unfortunately, hubby still seems to be stuck in the Stone Age. He probably had this sort of overheating problem on his first Stutz-Bearcat, and he never forgot it.

RAY: Assuming that the cooling system on your car is in good working order - and you would certainly assume that of a brand-new car - driving in city traffic with the air conditioner on should be no problem. Trust us. If air conditioners could only be used in cold weather, they'd sell a lot fewer of them.

TOM: So roll up the windows, Betty, and turn on the AC full blast. If your husband complains, tell him to take a hike. With your hairdo intact, you should have no trouble picking up a nice 19-year-old.

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