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Old 12-03-2002, 05:07 PM
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Join Date: Nov 2002
Location: Wakefield, RI
Posts: 2,145
Unhappy "Another" Climate Control question....

Hello all, I just returned from NC where I picked up my "new" '84-300D and drove it home. I have read the manual and I am still having a problem with the climate control. Cruising on the highway in 45-55degree weather the climate control worked fine. If the car sits and idles the climate control works perfectly, even in the much colder North, >20degrees. Unfortunately the faster I drive the less the climate control seems to work. The fan just increases speed as the system tries to keep up but it just blows lukewarm air at highway speeds. If I then pull over and idle for a few minutes the air warms up very quickly. The Thermostat is new and the temp gauge works and is not fluctuating at all. Any help on this would be great. I need heat this winter! Thanks, RT

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Old 12-03-2002, 10:01 PM
Registered User
Join Date: Nov 2002
Location: Wakefield, RI
Posts: 2,145
Well, rolled home from CT to RI tonight. The heat issue is unchanged. What controls the amount of heat? If I put the temp on "max" and set the fan on low the air coming out of the ducts is quite warm even at highway speeds. There is just not enough of it to warm up the car. If I turn up the fan higher it cools off leading me to believe there is not enough flow through the heater core? Is there a valve or something that controls the amount of hot water or air (however this system works)?? Help!! Its in the teens here and I need to drive this thing!! Someone here has to know how this works? Thanks, RT
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Old 12-03-2002, 11:44 PM
MVK MVK is offline
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Join Date: May 2002
Location: Queens, NY
Posts: 447
There is a valve called monovalve. Check this forum for how it works. Also check under my name MVK as I had in past posted the photo and other relevant info. Too much to type again. Also do it yourself pages tell you how to change it. about 25 bucks for the valve repair kit. No need to buy the whole valve.

One penny saved is three penny earned.

1985 300D Turbo 179,000miles
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Old 12-04-2002, 08:19 AM
Posts: n/a
Most likely your problem is the foam hose on the temp sensor. Remove the glove box and you will see a horizontal pipe that goes to the left. There is a foam hose that connects it to the temp sensor grill assembly in the center of the dash. Go to Home Depot and get 3/4" foam pipe insulation and replace this hose.

Good luck,
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Old 12-04-2002, 06:13 PM
Registered User
Join Date: Nov 2002
Location: Wakefield, RI
Posts: 2,145
Monovalve rebuilt today. Very easy to do. Climate control appears to work perfectly now. Thanks again all!! RT

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