Heater Blowing Cold Air

wmrra82

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Washington State
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'95 Buick Roadmaster
Thread starter #1
Hey All... I've had this car about a week now, 1995 Roadmaster White w/Blue interior, 117K miles original. I was told the heat hasn't worked for about a year and a half. Driving to work can be rather chilly but bearable, haha. This is where I'm at so far with my diagnosis... In diagnostic mode #8 I watched it climb from cold to read 182 degrees so my thermostat or water pump (whichever this reading is for) seems to be getting warm. Both my heater hoses going into the firewall are warm, not hot, but both warm. Passenger side fan is running all the time, while driver side does not come on while just idling in driveway. I see that it uses the DEX-Cool coolant in this vehicle so I'm wondering if there is a clog down the line. I reverse flushed the heater core but it didn't really look too bad. When I looked into the reservoir, it looked pretty scank. I removed it and flushed it to make sure all the passages where clean, then reinstalled. Ran car to bring up to temp, used bleeder valve anytime I disconnected any hoses...still cold air. Almost acts like a radiator that just low enough on coolant to pump it back through the engine but after topping off, heat returns. Is there a better way to purge the air from the system I wonder? Anyway, replaced thermostat just to see what coolant looked like in there, but it too, wasn't too bad. The worse build up of crud was in the reservoir, but anyway...still no heat just cold air. The funny thing though was when I was getting into the car after letting it idle for 10 minutes, it was actually warm between the car door and the interior as I sat down...checked the vents...still blowing cold air. Hmmmmm. I looked under the dash briefly, as it's dark out now to see the actuator to see if it was working when I changed from Middle to Floor to Blend, but the actuator seemed to be moving in the various modes. Does anyone know, is there a separate door for heat coming from the engine? Anyway, not sure where to check from here on out. Any directional pointing gladly accepted. Thanks..
 

Logjam

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Buick
#3
My '96 is doing the same thing. I haven't started a full blown diagnosis yet, but I've noticed that the temp gage runs on the hash to the left of center. I noticed today, while in line at McDonalds, that the temp jumped up to the right of center and quickly back to the left as soon as I started moving. Another thing that I've noticed is that if the fan speed is low, I can get some heat out of it. This whole situation reminds me of a similar one I had with a '97 Bonneville. It would blow cold in the winter and hot in the summer. That ended up being a cracked gear for the temp blend door. Needless to say, that was quite a job, as the whole dash had to come down. If this car uses the same, or similar, type of plastic gear for the blend doors, I may by suspicious of that. I'll let you know what I find.
 

HotZ28

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Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
#4
Does anyone know, is there a separate door for heat coming from the engine?
The same door actuator is used to switch air flow between the A/C evaporator and the heater core. Did you you run any system coolant flush through the whole system? Mine was partially blocked and it took a long time for the cabin to get warm. I flushed the whole system, then added Prestone system cleaner and drove for it for about 50-miles, then did another flush, drained & added coolant. It now heats much quicker & warmer in all settings. There is a a small orifice in the line going to the heater core that may be blocked by Dexcool sludge.
 
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