Heat problem

[97ramparente]

Hey everyone I'm new to the forum.. But here my problem I am having I know winter is not here yet but for the last couple years my truck 1997 Dodge Ram 1500 v85.2 I have had poor heat in my truck... last year I replaced radiator, water pump,thromstate, heater hoses, heater core, coolant flush and cleaner a couple of times everything in the coolant system is fairly new. When I replaced the heater core I inpected whatever I could see in the heater box blend door and everything seemed good. I bleed the system to get trapped air out. I have no overheat problems temp is always right at 200 degrees I'm at a loss I don't know what else I can do or check to figure out the problem is. Also my a/c works fine so I have no clue what else to do I would appreciate any advice from anybody thank you!

 

[dudeman2009]

Did you check to see if the blend door is moving?

First thing I would do is start it and warm it up to operating temperature. Then turn the heat all the way up and give it a couple minutes. Then feel the heater core hoses, both should be hot. If they are, then my bet is the blend door.

You can check the blend door by putting the truck to run and turning the fan controls to the off position. Then stick your head near the floor in the center of the dash, or by the pedals and move the temperature selector from all the way hot to all the way cold. You should hear a tiny little motor moving.

If the heater hoses are either slightly warm or not warm at all, you have a blockage somewhere. We do not have heater hose valves, the heater core is constantly supplied with engine coolant.

Make sure no hoses are kinked.

You can pull both heater hoses if you suspect a clog and try to flush and backflush just the heater core.

 

[97ramparente]

Thanks man but when I changed the heater core I checked the blend door and it works properly and it's on a cable not a blend door motor... Hoses aren't kinked I don't know what else to do

 

[dudeman2009]

Thanks man but when I changed the heater core I checked the blend door and it works properly and it's on a cable not a blend door motor... Hoses aren't kinked I don't know what else to do

Are both hoses hot? If they aren't you are tracking down a low/no flow problem. If both hoses are hot, you have a problem with getting air through the heater core. I've seen cobwebs and mice nests cause problems.

 

[97ramparente]

Both hoses are hot and I replaced the heater core and everything was clean

 

[dudeman2009]

Both hoses are hot and I replaced the heater core and everything was clean

If both hoses are hot, it seems you have a problem with either moving air to be heated, or getting the heated air where it needs to go.

I've never taken apart the dash to get into the air system on a Ram, cant help with pointers there. All i'll be able to tell you is what I see from pictures in the service manual.

The only thing I can come up with is a block either right before or after the heater core, but not so far back as to stop airflow from the fan. Perhaps something was assembled wrong, or the AC never shuts off and the heater core cant overcome the coldness from the evaporator. Does it get better if you set it to simply face instead of AC?

Otherwise i've got no clue.

 

[97ramparente]

I have good air flow thru vents and they all work properly.. Whatever setting I put the air to come out floor,vents,defroster all is good and I replaced the heater core and the box inside was clean I'm just stumped and don't know what the heck else there can be wrong

 

[dudeman2009]

I have good air flow thru vents and they all work properly.. Whatever setting I put the air to come out floor,vents,defroster all is good and I replaced the heater core and the box inside was clean I'm just stumped and don't know what the heck else there can be wrong

The problem i'm faced with is, there are no such things as ghosts. The heat is going somewhere, into something.

Sitting back and looking at this. You say the engine runs at 200*F. So your coolant should be hot as hell. I run a 180* Tstat and sometimes in the winter my heat feels lacking, but its still hot. My heater core hoses are too hot to hold, so should yours. If you have a thermocouple or non contact thermometer, check the temps on your radiator inlet and heater core inlet. They should be almost the same. The outlet for the heater core should be within 20ish degrees with the fan off.

What vents do and do not work are of little help unfortunately, all of the switching controls are after the problem area.

There is air flow, as is evident by cold air moving through the vents. There is at least no blockage along the main pathways.

There may be a problem in the snake like passage that the air must flow through to pass through the heater core.

When you switch the vent from hot to cold, does the sound/flow of air change as if a baffle is redirecting it? If not, the blend door may have become disconnected, or a cable loose, causing little to no adjustment.

Unfortunately, without a bore scope you cant look at the dumb thing without taking it all apart.

Was there a plastic film on the heater core that might have not been removed? Did all the fins look clean? Did someone install a bypass valve somewhere in the engine bay? Was anyone helping you who could have accidentally bypassed the heater core in the cab with a small section of pipe?

It has to be something. Unless you found the holy grail of air conditioning accidents, the ability to turn air from near 200* to a luke warm feeling in seconds.

 

[97ramparente]

I appreciate all the help man like you said heater hose are hot as hell there no bypass or anything hoses go straight from the motor to the firewall like they should when I replaced the heater core I made sure there was no plastic or anything blend door looked in good shape no cracks or anything and it's fully functional.. The only thing that is odd when I run the heat for Alittle and if I feel the bottom of the heater core like the plastic houses of under the dash it's not warm.. Like you said there could be s passage way of air getting in there somehow but I checked everything I could of checked when I had the old heater core out

 

[dudeman2009]

I appreciate all the help man like you said heater hose are hot as hell there no bypass or anything hoses go straight from the motor to the firewall like they should when I replaced the heater core I made sure there was no plastic or anything blend door looked in good shape no cracks or anything and it's fully functional.. The only thing that is odd when I run the heat for Alittle and if I feel the bottom of the heater core like the plastic houses of under the dash it's not warm.. Like you said there could be s passage way of air getting in there somehow but I checked everything I could of checked when I had the old heater core out

Baffling The whole heater core should be hot. Even the plastic right next to it should be hot. If its not, i'd start to suspect the heater core. Unfortunately it seems like you are going to need to liberate the heater core again, or at least gain access to be able to determine if it is hot all over or just across a small portion. Its not unheard of for new heater cores that have been wave soldered together to be problematic. It could be that some of the internal passages are blocked enough to make the heat suck but not enough to keep the heater hoses from getting warm.

 

[97ramparente]

Yeahhhh if I feel the bottom of it it's not hot it's almost like the fab is cooling it down put I don't see how that is possible with constant hot coolant running threw it.. And if I put my fan on low there some heat out when I put it on high there's little heat.. I guess my only option is to get into the dash again and see what's going on with it

 

[pmk138]

Hello, I was just wondering if this has been solved. I have 1999 dodge Ram with the same heat issue. I have not checked the blend door yet, but that will be one of my next moves. I suspected the HVAC controls, but I haven't check that either.

 

[Coletrain523]

Ok so my truck is doing the same thing. All the fan settings work. It has coolant. But no heat. If the fan is on low there is slight warm air, but as soon as I go up a speed it blows cold. I checked the heater core hoses and one is about 160-170 and the other is 120-140. The first hose is pretty consistent at 160-170 but the other hose (according to the laser temp) can be anywhere from 120 to 140 or 150? So would this mean the heater core is clogged or there is a blockage in the system? The radiator was just replaced maybe 4-5 months ago and was all flushed at the time of replacement.