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Discussion Starter #1
Not too long ago I noticed the heater in my 159 gasser PM wasn't working. Looking briefly online led me to check the coolant which in fact was just below the low mark. I topped it off with the proper coolant but the heater still doesn't work. To clarify - the blower motor works just fine as does the blend door actuators to go between defrost/front vents/ lower vents. I turn the dial to heat but even with the engine hot it just blows out ambient temperature air.

I'm guessing an airlock somewhere in the system but if that's the case, I'm not sure how to bleed it. Any thoughts?
 

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Discussion Starter #3
Promasters typically show the coolant level slightly under the min mark so, as you discovered that isn't your problem. It's probably caused by a vent not working correctly. Some people have reported the same problem in the past.
Can you explain what you mean by a "vent not working"?
 

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Or a vacuum leak to the valve that opens and closes the valve that sends hot coolant to the heater core. Maybe faulty control knob on the dash. ?
 

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My understanding is the heater return hose has hard 90 degree turn with a bleeder by the firewall.
 

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My understanding is the heater return hose has hard 90 degree turn with a bleeder by the firewall.
Can anyone confirm that? I was just wondering what the little black knob was on the hose with the hard 90 degree bend. If that's a bleeder, it makes sense that it's the return hose.
 

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Gee Steve, you can. Turn the knob?
 

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Discussion Starter #11
The black nut deal at the 90 does bleed coolant when loosened. I've messed with it a bit without success in getting the heater working.
 

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There are two bleeders/burpers on the pm. One is at the thermostat (under the big engine mount) and the other is at the firewall as you discovered. Burping needs done first so you can rule it out.

But your problem is likely the blend door. The blend determines heat or ac, and the mode door determines feet, chest, or dash defrost. I currently have a sketchy mode door on one of my pms.

The doors are controlled by the computer and are little stepper motors. As such, a dealer or well ewuppid shop can hook up to the computer and command the doors to do what they want. Thats how they diagnose a bad door. That confirmation is what I'd want before I start tearing into the dash. I cant imaging it would take a tech more than a few minutes with just his laptop.
 

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Discussion Starter #13
There are two bleeders/burpers on the pm. One is at the thermostat (under the big engine mount) and the other is at the firewall as you discovered. Burping needs done first so you can rule it out.

But your problem is likely the blend door. The blend determines heat or ac, and the mode door determines feet, chest, or dash defrost. I currently have a sketchy mode door on one of my pms.

The doors are controlled by the computer and are little stepper motors. As such, a dealer or well ewuppid shop can hook up to the computer and command the doors to do what they want. Thats how they diagnose a bad door. That confirmation is what I'd want before I start tearing into the dash. I cant imaging it would take a tech more than a few minutes with just his laptop.
Any special technique for burping? Previously I've let the engine heat up then crack it for 10-20 seconds while it bleeds coolant then tighten it back up. I haven't done anything with the bleeder by the thermostat yet.
 

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Mine quit working. There was a door or gate that was getting stuck closed and blocking the flow. The used dealer tried to fix it by lubricating it but ultimately I had to replace it.
 

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Discussion Starter #17
Just bled both bleeders - I did the one by the thermostat while cold and confirmed it was full then started the van and bled the one at the firewall. No change.
 

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So, now that you know where the heater hoses go thru the firewall, you should feel them for heat.
When the motor is hot and the heat is turned on and fan blowing,
feel them hoses. At least one of them ought to be hot like the coolant.
If NOT, then its a valve not opening thats supposed to send hot coolant to the heater core.
Check that switch.? Or find that valve.
 

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I don't think there is a valve, the diagrams don't show a valve that I can find.

El Guapo or a mechanic replace his actuator or blend door wasn't clear to me, time? effort? cost?

So you can assume it's not air locked.

You still need to figure out if the blend door is working. It looks like the actuator is on the outside of the HVAC housing, passenger side(parts diagram) and it has a shaft with splines that I'm guessing is attached directly to the blend door.
If the actuator is bad I would think that it would throw a code.

http://www.carparts.com/details/Ram/ProMaster_2500/Replacement/HVAC_Heater_Blend_Door_Actuator/2014/REPD410201.html?TID=gglpla&origin=pla&gclid=EAIaIQobChMIpYT0hsKy1QIVCzBpCh0S2wOYEAQYBSABEgIEx_D_BwE&gclsrc=aw.ds

The only way I know to check for a clog is to reverse flush the heater loop.

If you never mess it the coolant system and your below 150k I don't see a clog happening.
 

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A quick review of the PM service manual says...

A hunt for wiring harness plugs being loose would be time well spent...

There are three 'doors', mode and blend door actuators have position sensors and recirculate does not. A scan tool will show Diagnostic Trouble Codes (DTCs) for those items. The mode actuator is behind the glove box, the blend door behind the steering column cover and the recirculate door requires the whole HVAC box to be out on a bench.

The two doors with position sensors call for dealers scan tool recalibration if they are replaced. It is likely that would be needed too if the motor(s) got disconnected and HVAC controls were changed, the positions would be unknown to the HVAC control head module. I've read where their calibration can be corrupted by flawed module reflash procedures but I've little or no clues other than suspicion it could be possible.
 
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