No heat in your roadie? Read on....

Copied by permission from John D2



This (LONG) post deals with the troubles I had with my '96, with the automatic "dial-a-temperature" electronic heat/AC controls. I'm sure it'll apply to other years & makes with the same heating & cooling system.
(BTW - some of the following tests are done with the car running... take appropriate measures NOT to gas yourself dead if working indoors!)

I'm fortunate enough to have the 4" thick factory service manual for my car. There's about 30 pages devoted to HVAC problems & diagnosis. Without this book, you are basically screwed... there are multiple interrelated devices & gizmos in this HVAC system, all very difficult to diagnose..... unless you have the book or don't mind throwing parts, time & $$$ at the problem until you fix it.

The following is a summary of the tests I did, and the following assumes you have/had:
- a functioning heater until recently
- a functioning A/C compressor
- a functional A/C-heat dash controller
- NO trouble codes (DTC's) in the HVAC system... (see? need the d*mn book!)

I'm not going to guarantee this will solve your problem, but if you've exhausted the obvious "traditional" troubleshooting, this may help.

Symptoms:
#1 - System blows cold air regardless if set to Def, Blend, Floor, Middle, etc. (and air blows through appropriate/selected ducts & vents).
#2 - System blows cold air when set to 90 deg. & you have full/high speed blower motor.

Prelim.Tests:
#1 - Car is up to temp. Upper radiator hose is HOT!
#2 - Both heater hoses (to/from firewall) are HOT, with very little difference in temp. You can feel coolant flowing.
#3 - Bottom of A/C-Heater box in passenger compartment is HOT, especially towards the driver's side.
#4 - Blower motor "ramps up/down" corresponding to temp settings.

What was wrong with my car was the motor-driven temp controller (Electric Actuator). This little box turns a shaft inside the A/C-Heater box with a diverter door - directing airflow through either the A/C or heater core.
This little gizmo is about the size of a pack of smokes, roughly triangular in shape, and hidden on the front-face of the A/C-Heater box, between the glovebox & ashtray/junk drawer.... held on by 2) 5.5mm bolts.

Confirmation Tests:
#1 - Do all the "Prelim. tests".
#2 - Pull the glovebox & ashtray/junk drawer & find this little box/actuator
#3 - Watch the shaft through the hole in the actuator, and ramp the temperatures up & down...... does the shaft twist back & forth about 60 deg.??
#3 = YES... You've probably got a plugged heater core - OR - the diverter flap on the shaft is broken. Double check prelim. test #2, then proceed.
#3 = NO... Proceed to #4.

#4 - Pull the actuator box (leaving it electrically connected). Can you manually twist the shaft in the heater box?
#4 = YES... Nothing's jammed in the heater box - good.
#4 = NO... Find/repair the cause.

#5 - With the actuator box in your hand, ramp the temperatures up & down.... Does the white gear (visible through the hole) turn back & forth??
#5 = YES... The splines on the inner hole of the gear could be stripped or the gear is cracked.... continue on, and see “Repairing your Actuator” post.
#5 = NO... Probably bad actuator/motor drive... continue on and see “Repairing your Actuator” post.

#6 - By manually twisting the shaft, do you then get heat from the vents??
#6 = YES... Good, you've narrowed it to the controller or the actuator.
#6 = NO... Go back to the preliminary tests & check heater core fins for blockage.

#7 – With the actuator unplugged use a DVM at the actuator connector, check for battery voltage @ terminal 5 (Brown wire).
#7 = YES... go to #8
#7 = NO... check I/P (Instrument Panel) fuse #20

#8 - With temp set @ 90deg's, measure voltage at the actuator @ terminal 6 (Dk. Blue). Is voltage less than .5 volts?
#8 = YES... Actuator is probably bad
#8 = NO... Check for a short to ground on the dark blue wire, if OK the HVAC controller (dash display/button panel) is probably bad.

Whew! OK.... If this wasn't enough fun already...
You’ve got a few choices at this point:
1) Use some wire & manually tie-off the shaft to the "heat" position until springtime. (It will flop back to A/C-cold when you switch off the car.... don't ask me how I know....)
2) Buy a new actuator for big $$$ at Mr. Goodwrench
3) Scrounge a used (and unknown) unit at your favorite salvage yard
4) Repair yours. See my other post on repairing your actuator.

Hey everyone. REALLY sorry to reply to such an old thread but it's ONLY thread I've seen relevant to the searches I've been making.

The problem I have in my wagon is that the actuator only moves if I set the auto climate control to either FULL hot(all the way up) or FULL cold(all the way down). I can see it move 60° and I feel the temp difference, it's just that I can't get a littleheat or air, it has to be full hot or cold.

My question is, isn't this actuator supposed to have a full range of positions, not just two?

Thanks everyone...

Yes they have a full range of positions. Have you tried re-calibrating the unit? I'm at work and I don't have my Factory Service Manual but I think I can remember the procedure.

I think you have to disconnect the batter negative terminal for a few minutes (10 min). Then hook it back up, get in the car and start it up. the climate control unit should start a countdown from 30 wait for it to finish then crank the air all the way cool. let it run for one minute. I believe the manual says 30 seconds but I always wait a minute. Then crank the heat all the way to hot, and let it run for a minute. Once that's done it should be re-calibrated.

If I got any of the step wrong please someone else chime in I'm just going of what I remember. Like I said I don't have my FSM handy.

Plus I have a 93 and nowhereman appears to have a 95 so if the procedure is different please let him know.

95 is pretty much the same. Disconnect the negative for a few min, reconnect. Turn the ignition to run (don't know if starting it hurts or not, but this is how I do it). Do not touch the buttons on the climate control until its done calibrating which takes about 30 seconds. There will be no countdown, the only indication is the fan speed won't show any bars and you may hear the blend door moving if its quiet enough. It's done once the fan speed bars show up and the blower comes on.

Thanks guys. Recalibrating the unit did the trick. Didn't know you had to do that. I found another post and followed that - I unplugged fuse 33 (instrument cluster), gave it a minute or two, plugged it back in, turned the switch to on, gave it a minute, then started her up and drove to band practice. Worked like a champ.

Thanks again- I'm not sure sure I'd still be driving a car with this many miles on it if it weren't for this community. (Then again, I don't really like any newer cars as much as my woody wagon!)