[Thurman]

This is going to be a bit long but full of info on the old style canister/cylindrical heater control valve on a 2005 Titan, hopefully photos will be attached. For the sake of this discussion lets call the bottom part of the valve the "cylinder" and the top,square shaped part, the "head". I believe that the cylinder shaped part is a variable voltage solenoid valve. Problem: When the AC is off and the temp setting is all the way counter-clockwise I get very warm air coming from all the vents. IF I turn on the AC I do get cooler air but I believe it should be much cooler. When I use a hose clamp to clamp the hose going into the heater control valve the AC does indeed get much cooler. Using an infrared thermometer, no hose clamp, I get temps from the hose going into the control valve at a steady 95 degrees and the hose coming out of the control valve will be at 95 degrees. I'm sure that the control valve is stuck open. I'm the type that wants to know how things work so I take them apart to see how they work. I took the complete valve loose from the firewall with hoses attached, took the cylinder off of the head and did indeed find a real problem. There is a stem coming from the cylinder with a tapered head on it that seats off within the head portion. Let's say that when the stem is fully extended the tapered head seals off with a nylon looking tapered seat. When the stem retracts this allows coolant to flow to the heater core. This stem will turn but does nothing as far as moving. I can pull the stem out about 1/4" further and it retracts when I let go, maybe a spring in there. There was some type of rubber seal on top of the cylinder but it is damaged bad. I would guess the missing portion of this seal is somewhere within the heater core. My best guess is that this seal was designed to keep hot coolant from entering the cylinder/solenoid and that has been compromised. When I held the cylinder upside down and pulled the stem out and let it retract there was coolant coming from where the stem entered the cylinder. Another guess tells me that the coolant had caused a short within the solenoid. I tested the wiring connector for this valve and could not get any voltage with the truck ignition in the "ON" position and the heat control all the way clockwise for max heat. I will look for a fuse tomorrow. With the valve apart I did not crank the truck of course. I'm convinced that this valve is shot and cannot be repaired. After spending approximately two (2) hours on the internet and having no luck finding an exact replacement valve I started pursuing options. I did find an article that tells how to use a "Gates EHV114" heater control valve to replace this cylindrical style valve. The article stated that one could remove the hoses from the new Gates assembly, remove the old style valve cutting the hoses close to the valve and use the old hoses to connect to the new Gates valve. There is one small problem--the wiring connector on the new part is different than the old connector so one would have to do a work-around to wire in the new valve. They are both two (2) pole connectors, just different shapes and will not match up. I suppose one could cut off both the new and old connector and connect the two (2) wires together in some means paying attention to polarity. OReilly Auto Parts has the Gates EHV114 @ $123 and Amazon has the Gates valve @$99. I'm going to order from Amazon and try this set-up, more later as I do this. Hopefully this thread helps someone, , ,

 

[RICKSHAW31018]

This is going to be a bit long but full of info on the old style canister/cylindrical heater control valve on a 2005 Titan, hopefully photos will be attached. For the sake of this discussion lets call the bottom part of the valve the "cylinder" and the top,square shaped part, the "head". I believe that the cylinder shaped part is a variable voltage solenoid valve. Problem: When the AC is off and the temp setting is all the way counter-clockwise I get very warm air coming from all the vents. IF I turn on the AC I do get cooler air but I believe it should be much cooler. When I use a hose clamp to clamp the hose going into the heater control valve the AC does indeed get much cooler. Using an infrared thermometer, no hose clamp, I get temps from the hose going into the control valve at a steady 95 degrees and the hose coming out of the control valve will be at 95 degrees. I'm sure that the control valve is stuck open. I'm the type that wants to know how things work so I take them apart to see how they work. I took the complete valve loose from the firewall with hoses attached, took the cylinder off of the head and did indeed find a real problem. There is a stem coming from the cylinder with a tapered head on it that seats off within the head portion. Let's say that when the stem is fully extended the tapered head seals off with a nylon looking tapered seat. When the stem retracts this allows coolant to flow to the heater core. This stem will turn but does nothing as far as moving. I can pull the stem out about 1/4" further and it retracts when I let go, maybe a spring in there. There was some type of rubber seal on top of the cylinder but it is damaged bad. I would guess the missing portion of this seal is somewhere within the heater core. My best guess is that this seal was designed to keep hot coolant from entering the cylinder/solenoid and that has been compromised. When I held the cylinder upside down and pulled the stem out and let it retract there was coolant coming from where the stem entered the cylinder. Another guess tells me that the coolant had caused a short within the solenoid. I tested the wiring connector for this valve and could not get any voltage with the truck ignition in the "ON" position and the heat control all the way clockwise for max heat. I will look for a fuse tomorrow. With the valve apart I did not crank the truck of course. I'm convinced that this valve is shot and cannot be repaired. After spending approximately two (2) hours on the internet and having no luck finding an exact replacement valve I started pursuing options. I did find an article that tells how to use a "Gates EHV114" heater control valve to replace this cylindrical style valve. The article stated that one could remove the hoses from the new Gates assembly, remove the old style valve cutting the hoses close to the valve and use the old hoses to connect to the new Gates valve. There is one small problem--the wiring connector on the new part is different than the old connector so one would have to do a work-around to wire in the new valve. They are both two (2) pole connectors, just different shapes and will not match up. I suppose one could cut off both the new and old connector and connect the two (2) wires together in some means paying attention to polarity. OReilly Auto Parts has the Gates EHV114 @ $123 and Amazon has the Gates valve @$99. I'm going to order from Amazon and try this set-up, more later as I do this. Hopefully this thread helps someone, , ,

Thanks for posting this and for posting the photos. I have a 2005 TITAN and in the winter I was thinking that I wasnt getting as much heat as I thought it should be producing and was wondering about that heater valve assy on the firewall; whether it could be stuck. So...many thanks for posting and especially for the pictures; probably a project for a warmer spring day for me.

 

[Thurman]

Thanks for posting this and for posting the photos. I have a 2005 TITAN and in the winter I was thinking that I wasnt getting as much heat as I thought it should be producing and was wondering about that heater valve assy on the firewall; whether it could be stuck. So...many thanks for posting and especially for the pictures; probably a project for a warmer spring day for me.

From what I saw within the old style heater control valve: It appears that the old style valve is made so that when it is NOT getting an electrical signal it will be in the OPEN position, with the stem retracted. Variable voltage sent from the knob, with the blue and red markings, to the solenoid and will open the valve for heat as needed. I say this because I felt a spring within the solenoid/canister which pulls the stem to the OPEN position with no electrical signal. That is why my Titan was getting very warm air through the vents without the AC on and the knob set to the lowest temp setting. As I stated in one of my posts I used a heater hose clamp to stop the flow of hot coolant to the heater core and the warm air stopped coming out of the vents. I now have the "Gates EHV 114" heater control valve which I will use to change out the old style control valve. I've run into a problem as I cannot get any voltage from the wiring that connects to the old valve. I just spent two (2) hours tracing the wires to the control valve with no luck. I've checked every fuse that I can find no matter what it is marked for. Using the electrical schematic I am now looking for the "water valve relay", , ,