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2004 Suburban Poor Heating

Tom & Ray,

I am a new listener to your show, and I love it. I wanted to ask you both a question regarding my 2004 Suburban Heating system. This winter, the suburban seems to take a long time to turn on the heat. This in not how it was the last few winters. Given the temperatures in Chicago this year have been colder than the last few winters, it should not take that long for it to heat up. The heat usually starts to kick in when the temperature gauge gets between 160 and 210. When it starts to give heat, it is very slow until you put the fan to high for it to come out of the vents. Now is this a vacuum issue, or what would cause this to happen? I checked the coolant in the reservoir bottle, and it is to the full line. I cannot check the radiator as the cap is hidden under molding and I am not able to get to it. Do you have any suggestions on what to do or look for before taking it in to the dealer?



The best suggestion is not to go to a dealer at all. Just find a local, independent repair shop with a decent reputation (ask around). One likely possibility is that you need a new thermostat. This isn’t a big deal at all.

Thank you. I will go to my auto parts store and buy a thermostat and install it myself and see if this resolves the issue.

Thanks again

If you’re going to try to fix it yourself, then slow down a little - its not a good idea to just start guessing and throwing in parts. I just threw out “one” possibility with the real suggestion being not to assume that you need to go to a dealer.

First, if the reading on your temperature gauge is reading the way that it always has then I wouldn’t necessarily look at the thermostat first. If the temp gauge itself is reading lower than it normally does, then the thermostat is a good guess. (But keep in mind that the gauge itself can have problems).

Second, when is the last time you had the cooling system serviced? - flushed out with new coolant and all of that. If the answer is “never” because your vehicle has DexCool that is supposed to be “long life” - forget that part and have the cooling system serviced. Ask whomever does it to check the thermostat while they’re doing it.

Third, explain this better: “When it starts to give heat, it is very slow until you put the fan to high for it to come out of the vents.” Are you saying that the heat doesn’t really blow unless the fan is on high? That could be the resistor for your blower motor or perhaps even the fan switch itself - i.e. the problem might not be with getting enough heat - just with getting it to blow out.

When it starts to give heat, it is very slow until you put the fan to high for it to come out of the vents." Are you saying that the heat doesn’t really blow unless the fan is on high?

the heat barely come out of the vents unless you blast it to high, so I was actually thinking it might be a vacuum problem.

A blower fan that only blows on high is a classic symptom of a bad fan resistor. That is an electrical issue, but is normally very easy to take care of (easier than a thermostat).

With the fan not working a little bit of heat will come out just from air movement, and the movement is normally more when you’re moving as you’re forcing air through the system.

In terms of a vacuum problem, you might be thinking of a potential problem with your “blend door.” If that was the problem the air wouldn’t be warm whether blowing or not.

It sounds to me like you’re just missing all fan speeds except hi. The next time you’re in the car turn the fan switch to each speed and listen for the blower. If you don’t hear it/feelit changing speed with each click, replace the resistor.

I have a 98 Tahoe, much the same car. It has lousy heat. I have done all the things suggested in this line. None helped. I have concluded that it’s just designed that way. The only thing I have done that helped was to take a large black plastic trash bag; I duct taped it to the front grill, closing the hood over the top edge to help hold it and taped the bottom to the bumper. This has made the car run a little bit hotter–enough to get me somewhat better heat. I’m guessing I got another 10-15 degrees of coolant temp out of it, and it warms up a little bit sooner. The air now won’t blow straight in to the radiator, it has to come up from below. I have not had any overheating, but I plan to take it off when temperatures start regularly reaching 60 or so.

To be honest, the heating was great until this winter. I will check into the bad fan resistor. I will read up on this and see if it is something I can do, or if I have to take it into a mechanic to get done.