No heat!!! Thermosat?

[Buffalosports]

Well it is starting to get cool in the mornings, up north. The other day I turned the heat on and it came out almost as cold as the a/c. Back in the spring, it warmed up VERY fast. I would barely be out of the neighborhood and I had heat. Now it is freezing even after 15 minutes of driving. Somtimes I'll get heat for a split second and then it goes back to cold. This is generally when I first flip the switch. The anti-freeze is filled to the top. What could be the problem? Bad Thermostat?

 

[Buffalosports]

Anyone?

 

[MrShorty]

A bad thermostat is certainly one possibility. Is the engine warming up at all? How hot are the hoses?

Other things to look at would include the blend door and the heater core.

 

[Buffalosports]

I am gonna check the difference between the bottom and top radiator hose soon. That will narrow down if it is the thermostat. I was also thinking it could be a bad damper or one of the valves on the heat hoses can be bad.

 

[Swanny]

If youve never changed the thermostat Id say thats a good idea to check and change since its a cheap fix. My 96 had this same sort of trouble.

 

[FireZingr]

I'd say you have the dreaded Blend Door Broken!!!! Search Blend Door and you'll see how it can be fixed. If it is broken you'll either have 100% HOT air OR 100% cold air and nothing in between and no matter what setting you put it on it won't change.

 

[Buffalosports]

I am trying the easy stuff and then moving to he harder stuff. I am probably going to replace the thermostat unless I can prove it is still working. I heard something that there is a valve in atleast one of the heat pipes. Could this be either stuck open or stuck closed? Is there a way to tell?

 

[rookieshooter]

Drop the T-stat in hot water and see if it opens and then put it in cold water to see if it closes.

 

[Buffalosports]

Ok, set a side everything said so far. I Found tonight night that it does not seem to be the thermostat. I am getting ZERO heat in the cab. It feels like the A/C is on. Over the summer (of coarse when the temp. knob was always the way down on the bule side) I did a lot of work on my sound system and added lights under the dash. I am wondering if I pulled a wire or cable lose while feeding my other wires. Such as the wires attached the temp. control knob directly below the radio. I plan on pulling out the radio and checking the wires to the temp. control knob. My question is what is after those wires? Is there another type of actuator? Does this continue to be electronic? Is there a vacuum? Could it possibly be a fuse that is stopping a motor or an electronic device from working?

 

[BWilliams]

My question is what is after those wires? Is there another type of actuator? Does this continue to be electronic?

Someone indirectly answered this question for you earlier.

The problem is most likely your blend door actuator, which is a very common problem on the second-gens. What ends up happening is that it failed sometime over the summer when you had the temp knob on AC, now the door won't move back to keep you from freezing your ass off.

Searching on here will find you the instructions to repair this.

HTH.

 

[CDW6212R]

The AC control operates vacuum lines, check those well. Is the coolant in the radiator hoses hot? If you do go at the thermostat, be very careful with the sensors and housing under the T-stat. They are fragile and expensive, leave them in place.

 

[CDW6212R]

The blend door issue is supposed to be a 95-97 model problem, not for 98-01's. It's less likely for that to be the issue, start with the vacuum lines, and then the heater control valve.

 

[Buffalosports]

Someone indirectly answered this question for you earlier.

The problem is most likely your blend door actuator, which is a very common problem on the second-gens. What ends up happening is that it failed sometime over the summer when you had the temp knob on AC, now the door won't move back to keep you from freezing your ass off.

Searching on here will find you the instructions to repair this.

HTH.

Ok, I can hear the door moving inside the plentum (it seems), when flipping the knob. But NOT the common click, click, click noise from the broken gears. If I do replace it. Should I be looking to replace the door, the motor, or both.

 

[Buffalosports]

The blend door issue is supposed to be a 95-97 model problem, not for 98-01's. It's less likely for that to be the issue, start with the vacuum lines, and then the heater control valve.

The T-stat lines going into the core did get hot after sometime. That is why I don't believe it to be the thermostat. I would think I should be pulling atleast some heat.

 

[CDW6212R]

Check the heater control valve then, it has a vacuum line on it. If the lines are off under the dash, there will be a leak that you may not hear, plus the HCV will not work. You can see it(hard), under and behind the engine belt tensioner. Find the vacuum line up there near the right front and follow it down.

 

[Buffalosports]

Check the heater control valve then, it has a vacuum line on it. If the lines are off under the dash, there will be a leak that you may not hear, plus the HCV will not work. You can see it(hard), under and behind the engine belt tensioner. Find the vacuum line up there near the right front and follow it down.

So the HVC is near the tensioner? I am suspecting it is either the HCV (which I haven't checked) or something to do with that door/motor.

Is that HCV the two port or the four port? I am guessing the two port (it appears to have a motor on it). Where is the other located?

Pic of both:
http://www.partsamerica.com/ProductList.aspx?PartType=394&PTSet=A

 

[CDW6212R]

Mine is a two port, I think that all of these 95-01's would be the same. Night,

 

[Cobraguy]

Check the obvious. See if it's full of coolant. An engine low on coolant will blow cold air, then give quick bouts of heat as a little spurt of hot coolant reaches the core, cools off quickly, and goes cold again.

 

[FireZingr]

The blend door issue is supposed to be a 95-97 model problem, not for 98-01's. It's less likely for that to be the issue, start with the vacuum lines, and then the heater control valve.

My '98 Eddie Bauer has a broken blend door that I am getting ready to fix.

 

[budwich]

welll... if it is as cold you say, then check to see if your AC compressor is cycling.... then it is likely you have a blender door issue. Further, check the HCV hosing by grabbing / following the hoses for heat. IF you have none on some of the hoses... you have most likely found your problem. IF you have heat "everywhere there", then again, its mostly likely a door issue. good luck