No heat
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
Well, the heat is directed by the blend doors, that's for sure.
If you pull the radio and the defrost/vent plenum (two 8mm head screws under the dash, one phillips head to release the vent tube to the driver's side, and you can slide it down and out, cursing the designer the whole time ... or was that just me?) you can see the blend door for the temperature. With that, you can verify that the door IS flapping. Also, you can see the foam seals that seal the plenum to the HVAC box; those may be failing, but they're not part of the heater venting. (Heater tube is bolted to the bottom of the HVAC box with three 8mm, but I don't think you can take it off while the box is installed.)
I'm with HeyYou if you pull the HVAC box; also, consider the evaporator and the blower motor at the same time (for your cousin and mine, Justin Case). Seems like they've got a bad habit of failing within a year of you fixing one of the triad ... Jealousy, I think.
Also, a couple of sheets of thin foam (I ended up using strips of camper top installation foam, don't know how long it'll last) to replace the blend door foam, some 1/4" thick and some 1/2" thick foam for gaskets (to remake them), and you can make that HVAC box act like it's brand new.
Getting back to the water flow ... it might be supposed to go from the intake to the LOWER fitting, and the water pump to the UPPER fitting, so that hot water comes in the bottom of the core. I may swap them around that way when I swap the pump/heater core hose (I had to cut it to get the old one off, and the new one is barely fitting; too close for my comfort, but it DO get hot in the cab! We're also cycling around freezing, and had a low of 32F this morning, so ... not as much heat is needed to roast my toes. YMMV further north, where highs are still below freezing.) But no, the thermostat doesn't close that path off; getting back to that, the pump sucks water into the pump, expels it into the motor block. It runs around, cooling the block and getting hot, finally makes it to the intake manifold crossover. There, it feeds a) the heater core, b) the bypass, and c) the thermostat. The thermostat feeds the radiator, but notice there's NO blockage to the heater core (it's circulating even with the thermostat closed, being passed around it). With the thermostat CLOSED (as the truck motor is heating up), the water is being sucked by the bypass hose and the heater core. With the thermostat OPEN, there's still some water circulating both ways, but by that time, it's leaving the intake at the thermostat temp of 195F (and if you're running a 180F or even a 160F thermostat, well, yah, there's your problem ... )
RwP
If you pull the radio and the defrost/vent plenum (two 8mm head screws under the dash, one phillips head to release the vent tube to the driver's side, and you can slide it down and out, cursing the designer the whole time ... or was that just me?) you can see the blend door for the temperature. With that, you can verify that the door IS flapping. Also, you can see the foam seals that seal the plenum to the HVAC box; those may be failing, but they're not part of the heater venting. (Heater tube is bolted to the bottom of the HVAC box with three 8mm, but I don't think you can take it off while the box is installed.)
I'm with HeyYou if you pull the HVAC box; also, consider the evaporator and the blower motor at the same time (for your cousin and mine, Justin Case). Seems like they've got a bad habit of failing within a year of you fixing one of the triad ... Jealousy, I think.
Also, a couple of sheets of thin foam (I ended up using strips of camper top installation foam, don't know how long it'll last) to replace the blend door foam, some 1/4" thick and some 1/2" thick foam for gaskets (to remake them), and you can make that HVAC box act like it's brand new.
Getting back to the water flow ... it might be supposed to go from the intake to the LOWER fitting, and the water pump to the UPPER fitting, so that hot water comes in the bottom of the core. I may swap them around that way when I swap the pump/heater core hose (I had to cut it to get the old one off, and the new one is barely fitting; too close for my comfort, but it DO get hot in the cab! We're also cycling around freezing, and had a low of 32F this morning, so ... not as much heat is needed to roast my toes. YMMV further north, where highs are still below freezing.) But no, the thermostat doesn't close that path off; getting back to that, the pump sucks water into the pump, expels it into the motor block. It runs around, cooling the block and getting hot, finally makes it to the intake manifold crossover. There, it feeds a) the heater core, b) the bypass, and c) the thermostat. The thermostat feeds the radiator, but notice there's NO blockage to the heater core (it's circulating even with the thermostat closed, being passed around it). With the thermostat CLOSED (as the truck motor is heating up), the water is being sucked by the bypass hose and the heater core. With the thermostat OPEN, there's still some water circulating both ways, but by that time, it's leaving the intake at the thermostat temp of 195F (and if you're running a 180F or even a 160F thermostat, well, yah, there's your problem ... )
RwP
Veteran
Joined: Oct 2017
Posts: 389
Likes: 19
From: central Iowa
Well, the heat is directed by the blend doors, that's for sure.
If you pull the radio and the defrost/vent plenum (two 8mm head screws under the dash, one phillips head to release the vent tube to the driver's side, and you can slide it down and out, cursing the designer the whole time ... or was that just me?) you can see the blend door for the temperature. With that, you can verify that the door IS flapping. Also, you can see the foam seals that seal the plenum to the HVAC box; those may be failing, but they're not part of the heater venting. (Heater tube is bolted to the bottom of the HVAC box with three 8mm, but I don't think you can take it off while the box is installed.)
I'm with HeyYou if you pull the HVAC box; also, consider the evaporator and the blower motor at the same time (for your cousin and mine, Justin Case). Seems like they've got a bad habit of failing within a year of you fixing one of the triad ... Jealousy, I think.
Also, a couple of sheets of thin foam (I ended up using strips of camper top installation foam, don't know how long it'll last) to replace the blend door foam, some 1/4" thick and some 1/2" thick foam for gaskets (to remake them), and you can make that HVAC box act like it's brand new.
Getting back to the water flow ... it might be supposed to go from the intake to the LOWER fitting, and the water pump to the UPPER fitting, so that hot water comes in the bottom of the core. I may swap them around that way when I swap the pump/heater core hose (I had to cut it to get the old one off, and the new one is barely fitting; too close for my comfort, but it DO get hot in the cab! We're also cycling around freezing, and had a low of 32F this morning, so ... not as much heat is needed to roast my toes. YMMV further north, where highs are still below freezing.) But no, the thermostat doesn't close that path off; getting back to that, the pump sucks water into the pump, expels it into the motor block. It runs around, cooling the block and getting hot, finally makes it to the intake manifold crossover. There, it feeds a) the heater core, b) the bypass, and c) the thermostat. The thermostat feeds the radiator, but notice there's NO blockage to the heater core (it's circulating even with the thermostat closed, being passed around it). With the thermostat CLOSED (as the truck motor is heating up), the water is being sucked by the bypass hose and the heater core. With the thermostat OPEN, there's still some water circulating both ways, but by that time, it's leaving the intake at the thermostat temp of 195F (and if you're running a 180F or even a 160F thermostat, well, yah, there's your problem ... )
RwP
If you pull the radio and the defrost/vent plenum (two 8mm head screws under the dash, one phillips head to release the vent tube to the driver's side, and you can slide it down and out, cursing the designer the whole time ... or was that just me?) you can see the blend door for the temperature. With that, you can verify that the door IS flapping. Also, you can see the foam seals that seal the plenum to the HVAC box; those may be failing, but they're not part of the heater venting. (Heater tube is bolted to the bottom of the HVAC box with three 8mm, but I don't think you can take it off while the box is installed.)
I'm with HeyYou if you pull the HVAC box; also, consider the evaporator and the blower motor at the same time (for your cousin and mine, Justin Case). Seems like they've got a bad habit of failing within a year of you fixing one of the triad ... Jealousy, I think.
Also, a couple of sheets of thin foam (I ended up using strips of camper top installation foam, don't know how long it'll last) to replace the blend door foam, some 1/4" thick and some 1/2" thick foam for gaskets (to remake them), and you can make that HVAC box act like it's brand new.
Getting back to the water flow ... it might be supposed to go from the intake to the LOWER fitting, and the water pump to the UPPER fitting, so that hot water comes in the bottom of the core. I may swap them around that way when I swap the pump/heater core hose (I had to cut it to get the old one off, and the new one is barely fitting; too close for my comfort, but it DO get hot in the cab! We're also cycling around freezing, and had a low of 32F this morning, so ... not as much heat is needed to roast my toes. YMMV further north, where highs are still below freezing.) But no, the thermostat doesn't close that path off; getting back to that, the pump sucks water into the pump, expels it into the motor block. It runs around, cooling the block and getting hot, finally makes it to the intake manifold crossover. There, it feeds a) the heater core, b) the bypass, and c) the thermostat. The thermostat feeds the radiator, but notice there's NO blockage to the heater core (it's circulating even with the thermostat closed, being passed around it). With the thermostat CLOSED (as the truck motor is heating up), the water is being sucked by the bypass hose and the heater core. With the thermostat OPEN, there's still some water circulating both ways, but by that time, it's leaving the intake at the thermostat temp of 195F (and if you're running a 180F or even a 160F thermostat, well, yah, there's your problem ... )
RwP
Wish I would have had time this year to address this but I didn't with family obligations and surprise house sales etc.
Steve
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
Well ... two things if you want to force recirc.
1) Two nuts, used a 7/16" socket, will loosen and remove the recirc vacuum cylinder.
2) With that, you can just tie it down with a zip tie or a chunk of wire (I'd consider an old coat hanger bent into shape), since it pulls down to activate. EDIT: Come to think of it, if you pull the cylinder down and under the HVAC box, then zip tie it there, it'll open the recirc door a good bit, if not all the way ... ENDEDIT
3) DO cap off or plug both the vacuum lines to keep from creating a vacuum leak.
That can be all done with the HVAC box in the truck, by laying on the back looking up at the box. The two nuts are at the bottom of the box, furthest to the passenger side.
I THINK there's a picture of that in my last set of pics; but I'll get one off my old box for you and post it later today.
RwP
1) Two nuts, used a 7/16" socket, will loosen and remove the recirc vacuum cylinder.
2) With that, you can just tie it down with a zip tie or a chunk of wire (I'd consider an old coat hanger bent into shape), since it pulls down to activate. EDIT: Come to think of it, if you pull the cylinder down and under the HVAC box, then zip tie it there, it'll open the recirc door a good bit, if not all the way ... ENDEDIT
3) DO cap off or plug both the vacuum lines to keep from creating a vacuum leak.
That can be all done with the HVAC box in the truck, by laying on the back looking up at the box. The two nuts are at the bottom of the box, furthest to the passenger side.
I THINK there's a picture of that in my last set of pics; but I'll get one off my old box for you and post it later today.
RwP
Last edited by RalphP; Nov 16, 2019 at 01:08 PM. Reason: Thought hit me right after SAVE clicked.
Record Breaker
Joined: Apr 2010
Posts: 1,745
Likes: 50
I have had MANY Chrysler products over the years. Cars trucks vans and Jeeps. I have had problems on a few of them with the temp regulation cable. On my cordobas and 78 fury, I just flip the valve on the heater control valve under the hood manually. On my 97 Wrangler the cable went to the blend door like it does on these Dakotas, and was in such a place that I could just reach under the dash and flip the door either way as needed, this was only like twice a year. But yeah, when that cable goes bad, you get the same thing as a bad thermostat or plugged core, and that is a cold ride. On my fury I only ever drive it in good weather months any more (need to keep that one out of the road salt) so the heat is moot on that car.... But the last time I tried the heat it would still roast me out of the car when the valve was open.