Heater blows cold even on manual set
Thread Starter
Lead Lap
Joined: Apr 2002
Posts: 405
Likes: 0
From: California
Heater blows cold even on manual set
Ok, I've read a few threads about this, but I'm a novice at this stuff so I need more help than that. 
Basically my heater blow cold regardless of setting. Not AC cold, just cool, like nothing's coming through from the heater core.
I think the thermostat is working because this problem is not just on the AUTO setting. Even when I fiddle with it manually I can't get anything warm to come out.
Now the weird part, if I turn the dial all the way up to read "HOT" and THEN push the button for AUTO, the AC comes on and it gets cold!!!
So do I maybe have both a bad thermostat AND a blocked heater core valve?
How do I check if the flow through the heater core is blocked or not? The car doesn't have engine coolant problems, and it just had a 130K mile maintenance a couple of months ago.
Ral
Basically my heater blow cold regardless of setting. Not AC cold, just cool, like nothing's coming through from the heater core.
I think the thermostat is working because this problem is not just on the AUTO setting. Even when I fiddle with it manually I can't get anything warm to come out.
Now the weird part, if I turn the dial all the way up to read "HOT" and THEN push the button for AUTO, the AC comes on and it gets cold!!!
So do I maybe have both a bad thermostat AND a blocked heater core valve?
How do I check if the flow through the heater core is blocked or not? The car doesn't have engine coolant problems, and it just had a 130K mile maintenance a couple of months ago.
Ral
Pit Crew
Joined: Mar 2002
Posts: 104
Likes: 4
From: FL
I had the same problem and I just bypassed the valve. On the valve there are two vacuum hoses on top. Just unhook and cross the two and you are set. In the summer do the reverse. Otherwise buy a new valve $250+. This is on my 93 SC400.
Thread Starter
Lead Lap
Joined: Apr 2002
Posts: 405
Likes: 0
From: California
Ok, valve bypass sounds like a good possible solution. I will definitely check coolant first, however.
I might replace the valve itself it that seems relatively easy to do. I appreciate everyone's help!
Ral
I might replace the valve itself it that seems relatively easy to do. I appreciate everyone's help!
Ral
Trending Topics
Driver School Candidate
Joined: Aug 2002
Posts: 10
Likes: 0
From: OR
To check the control valve, follow the heater hoses up to the firewall, I'm not sure where yours is but on a 400 it's on the passenger side, high up against the firewall..... have somone turn your temp control slowly from lowest to highest setting and back.... you should be able to feel or see the valve operating by sticking you fingers up underneath the control valve itself. If it's not moving you hve a problem..... not too big of a deal to replace but if I remember correctly, the part is around $250 (+/-?). Lot less expensive if all you have to do is add coolant.... if that's the case, it may not even look like you're low but, a pint of coolant will make all the difference so, top it off.
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Okay, I found which one the Heater Control Valve is.
I connected the long vacuum hose to the top of the canister.
What do I do with the other short hose? Just leave it disconnected?
And now I'm only getting heat when I'm on gas. What could this mean?
Does this mean, I have a bad HCV AND a bad water pump?
I desperately hope that it's not the case, because that's going to be over 1000 bucks combined at the dealer.
I connected the long vacuum hose to the top of the canister.
What do I do with the other short hose? Just leave it disconnected?
And now I'm only getting heat when I'm on gas. What could this mean?
Does this mean, I have a bad HCV AND a bad water pump?
I desperately hope that it's not the case, because that's going to be over 1000 bucks combined at the dealer.
Last edited by ChronoJ1; Oct 19, 2003 at 09:30 PM.
On the bottom of the unit is a little arm that moves inside the canister. you do not need to do anything aside of disconnecting the arm from the servo and manually moving the arm in the canister. your done.
Originally posted by O. L. T.
On the bottom of the unit is a little arm that moves inside the canister. you do not need to do anything aside of disconnecting the arm from the servo and manually moving the arm in the canister. your done.
On the bottom of the unit is a little arm that moves inside the canister. you do not need to do anything aside of disconnecting the arm from the servo and manually moving the arm in the canister. your done.