Possible idea for common heat/ac vac control problems

philip171 · 02-14-2006, 08:51 PM

My problem is that in my 98 3.0 4x4 manule ext cab ranger is that the heating control knob does not respond, the heater runs with the heat on full blast. Everything else is fine, vent direction and fan speeds work great. I have spent allot of time taking things apart and asking people and cant seem to get any idea, till tonight.

Its eather in two places is the problem in my case.... One is the control knob, its eletric, not vac, the wires are pluged in fine but the switch maybe toast. The other is where the eletric wires from the knob control the vac lines, I think I found it. Its on the passenger side right below the air filter box, 4 wires of the same color pattern that run to the switch come out here, then there are two vac lines running into a small control box with these wires plugged in. Anyone know what I am talking about? Is this where the vac is regulated to control how much coolent flows through the heat exchanger that in turn determins how hot the air is? Any help would be great! And a name for this part would be to....

rbudde · 03-13-2006, 06:11 AM

I think I am having the same problem. all I get out of the "vent" setting is very hot air. I replaced the control unit thinking the temp control section wasn't working and the issue did not improve. I am thinking it is something to do inside the air handling system, but don't know anything about this. Did you figure out your issue?

Krok · 03-26-2006, 03:47 PM

My 97 Ranger had the same problem, as soon as the engine warmed up the heat was on. The temperature control knob didn't work but the flow selection knob did. So I replaced the heater core flow control valve which allowed me to shut off the heat but not control the temperature. This lasted for about 6 months before I was back to the original problem. I haven't fixed it yet, but I'm thinking it's a vacumn leak. Gotta love them vacumn lines.

philip171 · 04-17-2006, 05:46 PM

Thanks for the responce,
The issue is not yet resoved, I am thinking the problem is where the control goes from eletric to vacume under the air box. My air flow direction and fan speed knob all work fine. I also watched the coolent flow valve which regulates the temp in the heat exchanger, when I open the air flow direction knob to say floor, it opens the flow of water wide open so its full blast heat. If I turn it to OFF then it shuts it completly. If I switch to AC max, then it also shuts, strange? I am about ready to yank the vac hose off the control valve and hook a hose up and route it into the cab and I will suck on it while im driving to control my temp... Now thats strange.

Now it seems we all have the same problem, did you guys say you replaced the control knob in the cab? If so and it did not fix the problem, then I wont buy one. I think my next plan of action will be to find where the electric control knob controls the ammount of vac in the little box under the air box, replace that little box with a new one and see if that fixes it. Now the problem is finding out what that little box is called and where I can buy it. I do know it has a black vac line running into it and back out, and it has wires of the same color that come from the temp control knob.

Bill McKinney · 04-19-2006, 05:21 PM

I have a 97 ranger also with the same problem. I can run max/ac and get cool air but not on regular/ac. I replaced the heater exchange valve (4 port) and I still have the same problem. I was wondering if it could be the vaccum motor underneath the dash.

James Pagano · 07-16-2006, 03:40 PM

Hello Gentlemen,

I am experiencing the same situation. Max AC is full cold while all other settings are full hot. I have not yet looked for the previously mentioned control box under the air filter but i will check. If anyone has come across a solution, please let me know. I am considering taking it to Ford for examintation but am concerned about hours of diagnostic time to fix the problem.

Rangerblue · 10-23-2007, 07:30 PM

Say is anyone out there? I am Having just the opposite problem. Cold air all the time. Ath the other vents to floor, defrost, and head work fine. Just no heat!

jonmark1985 · 10-23-2007, 07:38 PM

Quote:

Originally Posted by Rangerblue

Say is anyone out there? I am Having just the opposite problem. Cold air all the time. Ath the other vents to floor, defrost, and head work fine. Just no heat!

Verify that your coolant is filled to the proper amount, and that your engine is running at the proper temperature. Not using a thermostat or using a lower termperature that OE will make the heater run abit cooler. If those appear fine check for a plugged heater core and that your heater control valve is opening properly. If all that still fails begin to check your vaccum lines for your heater assembly and that your blend doors are opening properly.

Rangerblue · 10-24-2007, 09:13 AM

Is the blend door accessible without removing the heater assembly? I removed my radio and glove box and located the vacuum operated floor , head, and defrost vents, but couldn't identify the blend door. There is not even any warm air coming through.
. Do you know if fluid travels through the heater core at all times, or just when the heater is used?

Dr.Hardcrab · 11-10-2007, 09:09 AM

Quote:

Originally Posted by jonmark1985

Verify that your coolant is filled to the proper amount, and that your engine is running at the proper temperature. Not using a thermostat or using a lower termperature that OE will make the heater run abit cooler. If those appear fine check for a plugged heater core and that your heater control valve is opening properly. If all that still fails begin to check your vaccum lines for your heater assembly and that your blend doors are opening properly.

I second that!

I have a '96 XLT Ranger and I had no heat. I came on this forum to see if I could find a starting place to solve my problem. My coolant overflow canister was at the '
full when cold' mark so I figured there was no problem with that. I started the truck up and after 5 minutes noticed that the main hose coming off the radiator was cold! Turned it off and let it sit a while and removed the radiator cap. EMPTY!!! How in the hell I ran down to South Carolina (from Maryland) 2 times without it overheating I have NO idea! I flushed the radiator, added the proper amount of coolant/antifreeze and water and SHAZAM! Working fine now....