Question about GMC Jimmy
If you are getting cold air blown out of the vents than you know the system is working fine, you just need that warm air. So, since the steps you have already taken have not work you must change or flush out your heater core and see if a bunch of gunk comes out, if it does you can just put it back in if you want. Depending on what year your Jimmy is, getting to the core is alot of work so you may just want to replace it to prevent problems down the road.
Posted on Dec 31, 2008
This problem is one i have encountered on a number of vehicle not just your brand. The problem seams to be in the controls switches and sending units. you have change lot of parts but did you check to see if you had flow through the heater core.Remove the heater hose's from the engine going to the fire wall. This is not precise in how you get the hoses off, however you do it? Once the hoes are off take a garden hose and try to run water throught the heater core. If you do not have a flow you need to find the closed valve. You may need to block off the hoses to the engine so you can run it for a vacume system. You may need to cut and put splices in the water hoses to do this. As a lot of engines you can not get to the end of the hoses.
This is not a simple fix as you would think. As i have found the heater hoses are getting warm or hot with the engine running but it is still cold inside the car. The word is no water flow no heat and if you have flow you have a vent door stuck closed. Air conditioner controls can have effect also. you may also may need to check the water pump out put to the heater core. This needs to be done with all the anitfreeze removed so as not to lose it on the ground. If you do remove the anitfreeze you can check the heater core flow by only removing 1 (one ) hose for the firewall to the heater. if you have hose off remember to put the garden hose in the radiator with it one as not to over heat the engine while it is running. you had heat before it a matter of tracking down where the flow has stop or the cause like a bad switch, broken wire or vacume hose.
Posted on Dec 31, 2008
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