AC blowing only on 0

[Stanislav]

Hi guys, I have a strange problem. The fuses all look good, but my heater/AC only turns on when the speed is at 0. Speeds 1 through 4 keep everything off. Also the mode selector does vary speeds, example Max is stronger than Norm. Also the center vents do not blow, only the side ones. What do you guys think it could be?

[Bitsyncmaster]

So with the fan on 0 do you get any air blowing? If so your fan switch must be broken.

[NightFlyer]

Or is the fan blowing, but you're just not feeling it out any of the vents?

Sounds like there are possibly two problems here:

1) No fan operation when selected, which could be a number of things - switch, resistor grid, relays, motor itself, etc.

2) Mode switch isn't opening the appropriate doors on the hvac box properly, which could be an issue with the spider plug or the rubber maze diaphragm within the switch.

[Stanislav]

So with the fan on 0 do you get any air blowing? If so your fan switch must be broken.

With the fan speed on 0 and the mode switch to norm or max I get air blowing. I also get air blowing when mode switch is on heater. Weird I know.

[Stanislav]

Or is the fan blowing, but you're just not feeling it out any of the vents?

Sounds like there are possibly two problems here:

1) No fan operation when selected, which could be a number of things - switch, resistor grid, relays, motor itself, etc.

2) Mode switch isn't opening the appropriate doors on the hvac box properly, which could be an issue with the spider plug or the rubber maze diaphragm within the switch.


Fan blows strong but only from the side vents and not the center vents when it is on Norm or Max, and when it is on Heater it blows out of the center vents. This all happens when the Fan speed knob is at 0, if I move it to 1,2,3,4 all blowing stops! I read that the fan speed control has 2 separate relays. One for speed 2 and 3 and one for speed 4, but why does it blow only on speed 0 and turn off on 1,2,3,4, makes absolutely no sense to me!

[NightFlyer]

Fan blows strong but only from the side vents and not the center vents when it is on Norm or Max, and when it is on Heater it blows out of the center vents. This all happens when the Fan speed knob is at 0, if I move it to 1,2,3,4 all blowing stops! I read that the fan speed control has 2 separate relays. One for speed 2 and 3 and one for speed 4, but why does it blow only on speed 0 and turn off on 1,2,3,4, makes absolutely no sense to me!

Put the actual blowing (moving of air) aside for a moment.

When you select 1,2,3, or 4 on the speed selection knob, do you hear the fan engage at all? In other words, at any of the speed selections 1-4, the fan is operating, but you're just not getting air flow out any of the vents.

Or, when you select a speed on the selection knob, the fan is not operating at all, except at 0, which should shut the fan off, but instead is having the opposite effect and actually engaging the fan? If this is the case, then I'm with Dave - the speed selection knob / switch is the most likely culprit.

When the mode switch is set to Max or Norm, the operable vents should be the face level vents and door vents. When the mode switch is set to heater, the operable vents should be the footwell vents, with a small amount of air being channeled to the defrost vents and door vents. As none of these modes are operating as they should, that tells me that the rubber diaphragm within your mode switch has most likely become unseated from the backing plate and is rotating with the knob. The rubber diaphragm could also be compromised and require replacement. You'll need to remove the mode switch and take it apart - only then will you know if the rubber diaphragm can merely be re-secured to the backing plate, or if you need to replace it with a new one from your preferred vendor.

As far as doing the mode switch repair, see these videos:


https://www.youtube.com/watch?v=17wN3KD71I0

[NightFlyer]

https://www.youtube.com/watch?v=358qaLbb-Sc

Best luck :thumbup:

[DMCMW Dave]

Going back to the original symptoms, I think you have two problems.

1 - "my heater/AC only turns on when the speed is at 0. Speeds 1 through 4 keep everything off."
The only way this can be true is if the fan speed switch is horribly broken inside or somehow connected wrong. I would pull the plug off the switch, and following the schematic, feed the wire for each speed in turn.
pink/blue - speed 1
pink/red - speed 2
pink/yellow - speed 3 (relay)
pink/black - speed 4 (relay)



2 - "Also the mode selector does vary speeds, example Max is stronger than Norm. Also the center vents do not blow, only the side ones."

The mode selector CAN NOT vary fan speeds. Only turn it on and off.
First make sure that the hoses are all attached to the back of the mode switch. Then take a look at the actuator for the center vent, located between the vent and the glovebox. Make sure the arm is not broken off. Then you will probably have to replace the diaphragm on the mode switch.
---------------
Is there a possibility that you have the terms reversed? The speed switch is 0-1-2-3-4 and is on the right. The Mode Switch is the one in the center that determines heat/a-c/vent etc.

One other thing to check - the three wires on the mode switch have to be connected the right way. In short the green wires connected to the ouside pins and the red one in the middle. It does not matter which green is which as long as the red is in the middle.

[Stanislav]

Just wanted to give you guys an update, the problem was the fan speed switch, figured out it was a VW part from the MK1 Golf so it was $11 instead of the $30 from delorean.com. Also plastic arm was broken thats why no air from center vents ;-)