Leaky heater core / AC?

[Zerohour3k]

Okay, here's the issue, and a question.

Just bought a new 300D (1983 300D Turbo), that runs pretty damn well. The car is 24+ years old, so it has a few issues.. but in all, not too bad. Rear windows don't work, A/C has a leak somewhere, and he stuck Euro lights on it. I like the city lights and all, but to be honest, I think the Euros make the car look too much like a generic 80's sedan.

Aaaanyway.. back to the issue. The A/C works, and the push-button controls were a refurbed rebuild within the last 35,000 miles. On A/C mode, the thing blows pretty cold (and sometimes TOO cold). Turning down the temp dial to the "white zone" doesn't seem to do too much in regards to making it less frigid in the car, and turning it down into the red zone makes the car smell musty for a little bit. Getting in the car in the morning, the inside windshield has a tiny bit of condensation on it. If I start the car and stick the thing on "EC" mode, it blows out humid air that fogs up my windows even worse. Even starting the car on AC mode will fog them up for a little bit.. before it clears up.

Obviously, this is gonna be one of three possible problems. The A/C hose is clogged, and not letting water drain from the heater core... the heater core leaks, or I have rainwater getting in the car.

Keep in mind that it's been INCREDIBLY humid outside recently, and that probably isn't helping any. If the heater core does have a small leak in it, can I just plug it with one of those "temporary fix" products? Do you guys reccomend any brand in particular? I don't really feel like paying an ungodly amount of cash for a heater core install.

[Douglas.Sherida]

Personally, I wouldn't use the "stops leaks" type of product. The principle of blocking leaks with goo, also tends to clog small necessary passages (e.g. radiator) and may lead to the car running too hot.

From your description of a "musty smell" it sounds like you have standing water, either from a leak or clogged AC drain. A heater core leak will smell "sweet".

Also coolant residue on the windshield is MUCH harder to clean off than normal moisture. It will leave a "greasy" residue.

[rrgrassi]

Do not use any of that leak stop crap. It does seal things it should, but also seals things it should not.

Do you get condensate dripping from under the car? Some of it does stay, and the musty smell you get is from dust and other things being "burned off" of the heater core.

Have you monitored your coolant level?

Does your AUX water pump work?

Check all that, and also put in a 1 amp fuse on the power lead that feeds the aux water pump. If the pump locks up, it usually fries the ACC pushbutton controller. If the pump is unplugged or wires to it are cut, chances are that it did lock up and took the prior ACC unit with it, hence getting the newer one you described.