Cal-OK

Please bear with me if this is covered elsewhere. If so, I can't find it. I'm a one week plus owner of a 1981 928 and am learning. When the weather got cold here this week I realized the temp slider will only hold at just under halfway from left to right (cold to hot). I can push it completely to the right, but it won't hold in that position. After a while, I get slightly warmed air from the vents. A/C and all vent positions seem to work well, just can't get the temp slider to hold. Manual is coming, but wondered if someone had advice.

soontobered84

Are you saying that the slider is moving from the position in which you are placing it? Or are you saying that the temperature is not warming as desired?

As a group, we normally tell all newbies to read all of the New Visitor information at the top of the landing page. Most questions that you have as a new owner will be answered there, however this one may not. More explanation of the problem may be necessary.

Speedtoys

Arent the early years a cable design, and maybe the mechanism for the mixer door is stuck?

jpitman2

The usual problem with the climate control systems (has an Auto position on the slide) is that you get full cold when the slide is full left, but as soon as its moved a little to the right, you get full hot air. This is usually caused by a disconnect between the internal and external temp sensors - commonly corrosion in the LH fender lead to the sensor. As above, your issue sounds like the slide is working its way back left by itself - please confirm! Also tell us if it has an 'Auto' position or not.
jp 83 Euro S AT 57k

Cal-OK

No, the unit doesn't have an auto position, simply a slide from cold to hot. You are correct, the slide won't hold in position. It won't hold past about 1/3 of the slide range. It doesn't go from cold to totally hot, just somewhat warm where the slide will still hold. Acts like it is spring loaded.

Thanks for any ideas. As I noted, I haven't seen this on other posts (but may have missed them), and it wasn't covered on the new member information I read.

jpitman2

Hopefully somebody with experience of the mechanical heater controls chimes in. Sounds like one of the cable controls is frozen and pushing back. I suggest you remove the console side panels and see if the cables are visible and accessible. Move the slide and watch how the cables react - if one bends and resists, try to find the cable end and why its resisting - try working the end part by hand and loosen it. Apply some light oil to cable outer if its a wire spiral. Also look carefully at heater box in plenum at base of windscreen (engine side) for any signs of cables operating levers or shafts - have somebody move slider and watch what happens on engine side. There is very little in WSM on this type of heater control most is about the climate control versions, where things are activated by vacuum.
jp 83 Euro S AT 57k

Cal-OK

Thanks, I will check the out! Makes sense to me.

Dmhager

The mechanical temp controls (hvac switch) have a small metal clip that holds the cable sheath against the plastic frame of the hvac switch so it stays rigid when the blend door cable is actuated. If the clip is missing or the plastic tab on the hvac switch is broken you will have this problem. Btw, it's a PITA to put it back on.

Hey_Allen

I was about to mention this as well.
In looking at my car's blend door slider for the same behavior, I found that the plastic tab that the clip secures to had broken off.

Now to figure out whether it's something that I can just put a zip-tie on to fake it, or whether there is some more elegant solution to the brittle old plastic issue.

Cal-OK

Sounds like fun! I'll check it out - when the weather warms up. Thanks!

Mrmerlin

I used a zip tie and a soldering iron
once i figured out where the cable housing needed to be anchored
I then made a hole into the rear area of the HVAC head with the soldering iron, this takes seconds.
once things cooled off,
a ziptie is now fastened to the board and the cable housing is held solidly now the A/C and the heat work

Cal-OK

Great idea! I'll give it a try.

Thanks!

Cal-OK

After spending an hour or so trying to come up with a clever clip to hold the cable housing in place, and failing, I went with your suggestion of a cable tie. Works well, the soldering iron melted a hole and away we go. Of course, one thing leads to another. I found two very small vacuum lines that were disconnected. I can't see where they go, so waiting for my cd manual from Jim to arrive. Heater now works, though.

Thanks!

Dmhager

Cal-OK

Thanks, Dennis!