I would also suggest that coolant is in fact circulating thru the heater core causing the heater hoses to be hot. The plenum door is probably closed due to a perceived warm condition caused by a faulty sensor. If the ambient outside temp sensor or the in-car temp sensor are shorted it will cause the system to run maximum cold. Also, if the control dial potentiometer is open it will have the same affect. Ken 67 Crown 4 Dr Ht 68 LeBaron 4 Dr Ht -----Original Message----- From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Kenyon Wills Sent: Saturday, March 31, 2007 6:24 PM To: mailing-list@xxxxxxxxxxxxxxxx Subject: Re: IML: 73 coolant circulation -- jhplc@xxxxxxxxxxx wrote: > Hi listers.. > > Soon after the ATC quit being able to change the > temp in the car( it is stuck on cool) and change > fan speeds..(unless switching from Lo to HI auto).. > There is no coolant going to and from in the heater > hoses...they get really hot and there is no coolant > in them,but the engine does not overheat because.. > The thermostat is new > The water pump is new > The coolant is new > The ATC servo does not leak > > This is puzzling because the temp gauge shows normal > operating temperatures ....any ideas > It is unclear to me what the question is. This is what I would say is happening based on your description: ATC II Servo failed, likely due to exposure to exhaust manifold heat or age/fatigue. Failure was not on the exterior, but was on the interior, letting coolant weep into the space above the passages - the mechanism that switches the flow or whatever, which is now corroded solid and non-operational. The water in both of the lines is not flowing because the valve is in the OFF position, but the water in the lines is touching the water in the block, and thus is getting thermal transfer via conduction. I predict that the water in the hoses heats up AFTER the water in the block heats up, but that it's difficult to discern the rate at which each heats up. They both get hot after awhile. The engine not overheating has no connection to the ATC II. You can bypass the ATC II or loop the hose connection back into the block with no downside. If you are asking if these conditions indicate a fried ATCII unit, the answer is yes. If you like having control over the heat in the car, you'd do well to get the aluminum replacement servo unit. See the site for that... The car will operate normally without an ATC II unit or a broken one so long as there is no leak. A failed unit is an indication that the plastic is weak and I encourage you to bypass the unit that you have until such time as you get a metal replacement to avoid a sudden loss of coolant that you fail to detect on the road that could be followed by an engine failure due to heat, signal sentry or no. You are a hose clamp away from avoiding a breakdown. I have bypassed all three servos on the ATC II cars that I own. It's nice enough here in Northern California that the windows regulate temperature well enough to allow me to ignore the irritation of the ATC II repair until I'm done with absolutely everything else. Kenyon Wills ____________________________________________________________________________ ________ Need Mail bonding? Go to the Yahoo! Mail Q&A for great tips from Yahoo! Answers users. http://answers.yahoo.com/dir/?link=list&sid=396546091 ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm