Mechanics

HEATING SYSTEM

1999 Chevrolet Blazer • 110,000 miles

Heater blows but not as high and not hot as it did last year. My chevy blazer is an LS 10 Limited edition/ 4door/ 4x4/ 6 cly. Does it have a Cabin Air Filter? Or, I have lots of dogs in and out of my veh on a daily basis. I've had the blazer since 2002.
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Gailstrail
November 6, 2013.



Heater blows but not as high and not hot as it did last year. My chevy blazer is an LS 10 Limited edition/ 4door/ 4x4/ 6 cly. Does it have a Cabin Air Filter? Or, I have lots of dogs in and out of my veh on a daily basis. I've had the blazer since 2002.

There is a number of components that can cause low heat performance and blower operation.
This particular system is set up with the evaporator first and then through or around the heater core. So air has to go through the evaporator first and then blow through or around the heater core. I suspect your evaporator fins are restricted because your not getting enough volume of air out of the dash vents and the temperature has decrease as well. Unfortunatly, gaining access to look at the evaporator is going to take some time due to having to remove components to gain access to see (if you have access to a borescope this will allow you to inspect the evaporator fins a bit easier) the evaporator fins. I think removing the blower motor and with a flashlight and a mirror you should see the fins once removed.

Your vehicle is not equipped with a cabin air filter.

As for the temperature blowing out the dash vents. Here are some possible causes for low heat output: a weak thermostat opening longer or stuck open will reduce the amount of heat stored in the cooling system because the cooling system is circulating constantly due to the open thermostat. Restricted or plugged heater core will reduce heat exchange into the passenger compartment. There are doors behind the dash that direct air blown by the blower that could be broken, stuck or the vacuum operated valve that controls the door could be stuck or leaking causing the door to no move when commanded to any more. A over-concentrated coolant/water mixture will not transfer heat as well or in other words if you have more coolant to water the heat will not be carried sufficiently (50/50 mixture is ideal in moderated temperatures. A 40/70 mixture is suggested in cold climates such as Alaska but no more than that). Restricted evaporator/heater core fins will reduce air flow and temperature by plugging fins and insulating these heat exchangers.
I hope this help you, let me know if you have more questions.

Ty Anderson
Nov 6, 2013.