94 Dodge Ram 1500 5.2


I know this subject has been beaten to death, I have read several other threads here with the same problem I have but I still can't get mine ironed out.


Heater takes awhile to get warmed up, even when the engine heat is up to operating temperature the heater gets warm but not hot. Especially when its on full blast.


Ive had this problem since I got the pickup. The engine was loosing a bit of coolant so I figured that caused an air pocket in the system causing the heater to only work ok. I replaced the leaking water pump, also replaced the thermostat/gasket while I was there.


Thermostat is operating ok, I bled the cooling system. Yet the heaters operation hasn't improved at all


I'm wondering if my heater controls are the problem? I can turn the dial to the floor or defrost or wherever and air just comes out everywhere no matter the setting. Meaning air always blows through the defrost vent/dash vents and floor vents all at the same time.

 

has your heater core been replaced? What about the control head?

All the vents are controlled by vacuum. Seems to me, someone would almost have to purposely screw things up for all the vents to get full flow...... (I think, even with the vents set on heat, you still get 10-20% flow thru the defroster...... but, shouldn't get anything at all thru the dash vents....)

Temp is cable controlled. You can feel the bottom of the axle for the temp (blend) door, on the bottom of the heater box, just to the passenger side of the trans tunnel. See if you can feel that moving when you twist the temp control. The temp door has been known to break loose from the axle......

If there is an air pocket in the heater core, backflush it. Process is outline in several threads. (and a couple recent ones.)

 

Heater core has not been replaced. I let the engine get up to operating temp last night and when and checked the inlet and outlet heater hoses and they were both hot (both were 175 degrees to be exact) I checked them with temp gun. When you ask if I replaced the control head are you referring to the climate control dials? If that's what your asking then no, plus I don't know if I can even buy a new climate control assembly.


All the vacuum hoses look like they are going to where they are suppose to and they don't seem to be leaking. Its weird.


I can feel the axle spin when I play with the temp dial, Is there any way the cable can come out of adjustment? like is it just not closing all the way when I turn it all the way over to heat?


I'm not sure if there is air in the heater core, I have bled the system more than once using methods recommended here in other threads. Question, I understand how back flushing can clean out a heater core blocked up but how is back flushing going to help get air out.....after I back flush I have to hook the hoses back up and rebleed the system using the method im already using.

 

You can find new (well, new to you at any rate...) control heads on ebay, amazon, or the junkyard...... I would hate to think what dodge would want for a 'new' one, if they are even available..... (probably should be sitting down when you ask how much. )

Does anything at all happen when you switch where you want the air to blow?

Grab the 95 service manual from this thread. (same as 94.) There is a procedure in there for adjusting the temp control Sure won't hurt to try it.

Heater core is, unfortunately, the highest point in the cooling system. Backflushing gives you the opportunity to have the hoses higher than the top of the core, so you can actually get all the air out. (thus, filling the heater core) The hardest part of that exercise is keeping as much fluid in the lines as possible, so you DON'T introduce more air into the system. No need to burp it again, as simply driving it a couple times *should* purge out any remaining air. (just check the overflow bottle every now and again.)

Something else you could try would be installing a flush "T" on the outlet side of the heater core (drivers side hose) as close to the core as you can possibly get. (yeah, way back in there, behind all the big greasy stuff, under the cowl..... great fun. Bring your arms with three elbows.....) Then, just start the engine, and BEFORE IT BUILDS PRESSURE, crack open the cap until (don't take it off) coolant flows steadily. That *should* also get all the air out of the core. (as the "T" will be the highest point in the cooling system.) Think I am going to try this on Saturday, as it will actually be above freezing..... and I wouldn't mind a bit better performance from my heater.

 

Thanks for that link there is more info in that manual than my vague Haynes manual. However it doesn't give any adjustment instructions for that blend door cable, just how to install it. Maybe you can't adjust it on a 94.


I'll pick up a used climate control next time I get to the salvage yard. Mine does act like its doing stuff (you can hear the vac shift/and sounds like doors are opening/closing it just doesn't affect the vents). When you switch it to recirculate it does make more noise and seems to be recirculating even though the air is still coming from dash and defrost vents.


Maybe the next step is to just back flush the heater core. That's a good idea, to add a bleeder valve up there. I always thought it was crazy that dodge didn't put a bleeder on the system even though the rad cap was lower than the core.

 

Turns out its in the 98 FSM..... here is a pic courtesy of zman. (RIP John.)