1998 Buick Regal Heater doesn't work.

Hi jlarson69. Welcome to the forum. Feel the upper radiator hose and the two heater hoses after the engine is warmed up. They should be too hot to hold onto for very long. If the heater hoses are cool, check the radiator hose. If it is also cool, the thermostat is not letting the engine warm up fully. If only the heater hoses are cool, suspect a plugged heater core. Back-flushing with a garden hose usually will clear the blockage. Also check for a water control valve if your car has air conditioning. They are controlled with a vacuum hose. These valves rarely fail but a break in the vacuum hose can prevent the valve from opening and letting hot coolant through. On most valves, you can see the linkage move when a helper switches between heat and air conditioning.

If both of your heater hoses are hot, coolant is circulating through the heater core. In that case, you can suspect a problem with the temperature blend door, it's actuator, or the control assembly. GM has real lot of trouble with electronic heater controllers, but if you have the older style levers and cables, diagnosis becomes a whole lot easier.

Caradiodoc

Unfortunately I do read quite a bit about heater / ac controllers causing problems. You're right about two actuators going bad at the same time. There is only one heater core but two temperature mixing doors. Most newer cars, (a '98 model is new to me), use electric motorized actuators instead of the previous vacuum motors or the even older, (and much more reliable) levers and cables. Still, the temperature doors normally move so slowly you may not hear them. The best way to tell if they're moving is to look for a linkage that moves in response to adjusting the controls. Some actuators don't use linkages so there's nothing to watch. Those actuators can often be unbolted and pulled out, then you can watch the shaft.

If your car does have vacuum motors, pull a hose off one and feel for the presence of vacuum while the engine is running and you adjust the controls. Temperature doors don't typically use vacuum motors because they are difficult to stop in specific positions. Vacuum motors are normally used for mode doors that are fully opened or closed.

With an actuator removed, you might be able to turn a temperature door by hand. Sorry I can't be more help on your specific model. I've rebuilt a few crash-damaged dual zone heater boxes, but those were all on 2006 and 2007 Dodge trucks. How about you buy a Dodge truck, then holler back when the heater on THAT one fails?

Caradiodoc

https://www.2carpros.com/forum/1999-buick-regal-blend-door-actuator-vt139193.html?highlight=

is it auto , daul zone you have