Engine/Transmission (1994 - 1998) No Heat in the Cab!

[edgeman]

As you all know I just put a new head on the truck and it is running better than ever. But one little problem... when I took the head off I tore the Tempature sending unit wire. I butt connected them back together and now my temp gauge only reads when i am sitting but it only goes to about 140 and when I am traveling down the road it doesnt read at all... . I also am not getting any heat in the cab when this happens... I only get heat in the cab when it is sitting... does the sending unit have any thing to do with the cab getting heat... let me know!

 

[kenny61]

if its really that cold you aint gonna get heat. If you got single digit temps wher you are put a piece of cardboard in front of the radiator and see if you can get the temp up

When I get my temp swings you lose heat (if its really cold out) right around 140* on the temp gauge

 

[hsmith]

Not the damaged wire, truck is not getting hot enough. Maybe the tstat is stuck open, or did you leave it out?

 

[The patriot]

Buck up

Awww come on!

My replacement heater core started leaking, so I havent had heat all winter.

 

[kenny61]

should have bought American

 

[edgeman]

lol I did not forget to put T stat in... . and it is in right... . and it is brand new out of the box when I put it in... . wouldn't low coolant do the same thing?!

 

[kenny61]

Low coolant would give you no heat but the engine temp would be high. Simple enough to check it... .

 

[dseabaugh]

My Thermostat stuck open 2 weeks ago. 50 mile trip and it still wasn't warm. See my post for the cummins part number on the new one. It runs easily 50 degrees cooler than the original one but seems like the more miles I put on the truck, the more towards the center of the gauge it gets when it is on it 'hi cycle' . the old one would swing back and forth on the guage to about 190. the new one swings back and forth to about 140.

 

[kenny61]

If the engine is only reaching 140* he aint gonna get no heat. MIne dont even start to feel warm until it get over the first mark

 

[edgeman]

And when your gauge swings it is a key sign of a head or head gasket going bad... . just thought I would warn you guys!

 

[Missouri Mule]

Tempature gauge swings for the 12 valves are normal unless you have upgraded the T-stat(Mine has been swinging since I've owned the Mule and I'm still using the oem T-stat.



Your tempature gauge or sending unit/wire fix is messed up.



Make sure your blend door (tempature door) is working.



Turn your selection switch to recirculation (max air) turn tempature knob to warm setting see if that will get you some heat.

 

[Skydiver]

edgeman,after you drive the truck for 10 miles quickly feel of the heater hoses. An IR temp guage would be handy. Also check for bubbles in the coolant recovery tank.



Block the radiator off. All but an 8" opening in front of the fan will warm things up faster.

 

[kenny61]

Go to your kitchen and "Borrow" your wifes meat thermometer you know the one sticks in the turkey at thanksgiving drop it in the radiator and see how hotits really getting

 

[dseabaugh]

Hey, I ruined one of the wifes thermometers about 15 years ago. I know better than to do that again. As to the swing, It swung like a pendulum for 13 years since new. Built in Mexico in '96. Cummins looked up the part via my VIn and engine serial number . I asked for the upgrade that didn't swing, but I got another 'swinger'.

 

[DSenn]

Can someone explain how to check and or adjust the blend door? How do you get to it? Is it adjustable from the temp control on the dash? I think this is exactly the problem I am having.

BTW, what is the engine temp with a new Mopar 5014568AA thermostat supposed to be? Mine is running at about 165 and I don't think it is hot enough.

 

[The patriot]

DSenn

I believe the blend door has to be inside the HVAC box.

W/O removing the box from the truck, I dont think it can be worked on or adjusted. Fact, I dont think there even can be an adjustment on it.

I had my box out to do the A/C condenser. I didnt even remember seeing it for sure, I wasnt looking for it. There was some door flap things in there. I just re installed them as I took them out and all was well.

You sure you dont have a vacuum problem?

Have you felt the lines running to the heater core?

I have the stock T'stat in my 98 12 valve and theyre usually around 180 going to the core. Shot with a infared thermometer.

 

[DSenn]

I checked all the lines I could see in front of the firewall. All of the face/floor/defrost/recirc switching seems to work. The out line of the heater core is HOT.

Just got Dodge to put a new Cummins t'stat in. Looks like a 195 degree cycler, but I can solve/reduce that with radiator blocking cardboard.

The output temps at the face vents are now about 20 degrees warmer, but the outside air temp is so warm I am going to have to wait until a colder day to tell any difference.