Hi guys,

I just picked up a beautiful 98 Ranger and the only thing I can find wrong with it is a HVAC problem. I bought the truck through the owners brother and they informed me that the AC would work if you "moved something under the dash".

So far, this is what I know:

The temperature out of the vents is full hot, all the time meaning even with the temp control all the way down to cool with the mode selector (Max AC/AC/ Vent/ Off etc.) in any position, all you get is max temp hot air out of the vents. The mode selector does seem to work in as much as it can re- direct the air to the proper outlets when it it operated.

At first I started looking at the AC system itself but now I think it's a control problem. The AC clutch relay, fuse, low pressure switch, clutch field coil, static refrig. pressure and power to the clutch circuit all look OK.

I poked around under the hood looking for vacuum leaks but there was nothing obvious and like I said, the mode selector works, so there's some source of vacuum for them. Also, The hot water valve is actuated when the selector is on the MAX AC or OFF positions as it should be.



Does this sound like a blend door problem? A bad temperature control? I am not well versed in this system and I'm wondering why even if the blend door is stuck or broken (an assumption), the AC compressor will not come on. I have already checked both the selector **** and the temperature **** to make sure they weren't stripped and spinning on their shafts.

Any suggestions would sure help, thanks!

 

Read FAQs above. Your Ranger's HVAC system is nearly identical to the F-series in function.

 

Boy, sometimes a combination of bad eyes and diminished common sense can really kick my butt!

When I initially opened up the relay box under the hood. I noticed that there was one loose relay just floating around in there. To a normal person, that would have set a red flag. Anyway, I looked at the legend in the owner's manual to locate the AC relay. The relays and fuses are arranged in banks and somehow (actually I know how, these eyes aren't what they used to be) I was looking at the wrong relay position and thought that the AC relay was installed. This afternoon I did a lot of staring at all the AC information and schematics on Alldatadiy and then while I was out poking around under the hood again. I referenced the legend molded into the cover of the relay box, and then checked the owner's manual again and sure enough, I was off by one bank of relays!. Of course the relay for the AC was the one that had been floating around inside the box! I plugged it in and immediately got clutch engagement and ice cold air! The deal is though, that I only get the cold air in the MAX AC position. Now I'm thinking that since I have no temperature modulation capability with the dash control, I'm relying on the fact that the MAX AC position operates the hot water control valve and shuts off water flow to the heater core in the MAX AC position. To back this up, If I switch the selector to the AC position, the compressor operation is still there, the water valve opens and the air output goes hot again.

This leads me to believe that it's either the temperature control itself, the blend door being stuck or broken or the electric assembly that operates the door to be faulty.

Next I need to figure out how to isolate the 3 culprits and repair this thing!

 

I'll speak to what I know about the E-Series HVAC system---some of it may transfer to your Ranger.........

Max A/C simply closes a damper that normally admits fresh air into the cabin, we used to call this recirculation. That position doesn't have any other effect.

I don't think there is a hot coolant valve, only the blend door which as you already know is controlled by the dash mounted Temp control, that door actuated by the drive motor mounted on the right side of heater core case. There is a pin point test for proper operation of the temp control, requires measuring the resistance as its moved through its range. Assuming that tests within limits its fine as is.

Next would be to remove the blend door drive motor, connect it back to the chassis wiring and watch it move (or not) in sympathy with the temp control.

Twist the blend door shaft to test if it moves freely--if not it needs replaced.

The loss of cool air when in Normal A/C might be a vacuum issue since much of the HVAC air flow is directed by servos relying on vacuum to open or close on demand.

Keep in mind I'm speaking mostly about my E-Series experiences with HVAC and its operation. If I'm too far off base please forgive and ignore all of this!

 

On a Ranger, MAX A/C also closes a vacuum valve under the hood to cut off the flow of hot coolant through the heater core. Most E/F-series trucks don't have this valve although it can easily be added.

 

Thanks Project---something I didn't know about the Ranger line---that's a good idea the E/F Series would benefit from having IMHO.

I'm in-process of adding this valve to my own E-Series, in the van forums its generally called a "cold air mod" and does make a difference. Mine will be on a separate switch, independent of the dash mounted Function Control.

 

Well guys, I cheaped out and bought the Dorman blend door. I removed the glove box, The connector was disconnected from the blend door actuator, so the first step was to re connect it and verify the operation of the actuator, which worked fine. Someone had pushed a big rubber vacuum cap over the drive shaft of the actuator and screwed it back in place so the essentially jammed the movement of the door. I cut out the bottom of the plenum according to the instructions on the blend door kit, removed the old door, which was broken where the actuator drive shaft went in and installed the new one. What I have described so far took about 45 minutes. Then I verified the door operation and closed the plenum back up again and re-installed the glove box. Not a bad job at all.
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Good job then----you'll have control of your heating/cooling now!

FWIW my Ford OEM manual for Econolines suggested procedure to service any part of the interior heater core components is to first remove the entire dashboard, including dropping the steering column! Plus Ford doesn't sell the blend door separately, just the entire heater core case.

Its comical knowing the real world fix is a lot less complicated and expensive!