1986 944 climate control unit

[markcigal]

Greetings all. I have finally gotten around to addressing my temp control issues. I have just installed a new AC compressor and have nice cold air once again. However, control or the temperature is very intermittent when I use the temp control knob. When I move the heat control valve under the hood, I can get steady heat or steady cold. The vacuum actuators seem to be functioning properly and each one registers vacuum. The clip is in place on the actuator rod and it moves to the proper position when the temp control knob is moved to full hot and then full cold, but the temp fluctuates all over the place. Is this a control unit issue ? If so, does anyone know where I can get this one repaired. Replacements seem to be difficult to find and VERY expensive.

Thanks, Mark

[Tom]

Have you seen our diagnostics for the HVAC unit?

viewtopic.php?t=357

Your issue 'could' be the control unit, for sure, but it could also be a temp sensor or solenoid or something else. The temp sensors are really just soldered onto the end of wires and I've seen them break loose and cause intermittent temp issues -- so worth running through the diagnostics in the link above. Could also be as simply as a scratchy temp pot/knob in the cc unit. Does it work fine at some temps but not on others (like dead spots on the knob)? Or more truly random (like a frayed connection)?

Lots of info here too...

[Evan]

Yes, this is a classic failure of the climate control unit itself. The internal circuit board develops cracked solder joints. Since the actuators work at the full hot/cold settings, your system is fine.

Search for an automotive electronics repair specialist or a Porsche independent shop. They can often repair your existing unit for a reasonable cost.

[Tom]

Yes, this is a classic failure of the climate control unit itself. The internal circuit board develops cracked solder joints. Since the actuators work at the full hot/cold settings, your system is fine.

Search for an automotive electronics repair specialist or a Porsche independent shop. They can often repair your existing unit for a reasonable cost.

The circuit boards are also connected via spindly little connector wires that tend to corrode and cause all the same issues as cracked solder joints. It's a very tedious process to separate the boards and replace those header wires, but can be done. I looked and have not found any shop willing/able to repair these units. ECU Doctors 'should' be able and willing since they rebuild the very similar 964/993 units, but last I checked they won't touch it. (And they charge $2,700 for the 964 unit. ). There are a handful of us who can save some of them, depending on what's wrong, and a few guys that offer rebuilds on occasion, but the world is still in need of a go-to rebuilder for these things. That said, I'd definitely run through the diagnostics to rule out temp sensor and solenoids. There's a good chance the cc unit is the problem, but easy and free to test other possible culprits before spending on a replacement...

[dlarsen944]

Control of the heat in my '86 n/a became uncontrollable last winter. It put out max heat all the time. After checking the linkages, etc............. I bit the bullet and replaced my AC/Heater control unit (9446530210301C). Purchased new from Porsche while attending a Tech Tactics session in Easton PA. Once installed, the control of the temperature was back to normal functioning.

PS. I purchased my 944 new with 25 miles. Now at 297,xxx miles, I got my money's worth out of the original control unit. Cost of the new unit was a bit over $800.

[blueline]

Control of the heat in my '86 n/a became uncontrollable last winter. It put out max heat all the time. After checking the linkages, etc............. I bit the bullet and replaced my AC/Heater control unit (9446530210301C). Purchased new from Porsche while attending a Tech Tactics session in Easton PA. Once installed, the control of the temperature was back to normal functioning.

PS. I purchased my 944 new with 25 miles. Now at 297,xxx miles, I got my money's worth out of the original control unit.

Cost of the new unit was a bit over $800.

Wow! Regarding both you and the 944, that is awesome and mightily impressive!

[Evan]

Yes, this is a classic failure of the climate control unit itself. The internal circuit board develops cracked solder joints. Since the actuators work at the full hot/cold settings, your system is fine.

Search for an automotive electronics repair specialist or a Porsche independent shop. They can often repair your existing unit for a reasonable cost.

The circuit boards are also connected via spindly little connector wires that tend to corrode and cause all the same issues as cracked solder joints. It's a very tedious process to separate the boards and replace those header wires, but can be done. I looked and have not found any shop willing/able to repair these units. ECU Doctors 'should' be able and willing since they rebuild the very similar 964/993 units, but last I checked they won't touch it. (And they charge $2,700 for the 964 unit. ). There are a handful of us who can save some of them, depending on what's wrong, and a few guys that offer rebuilds on occasion, but the world is still in need of a go-to rebuilder for these things. That said, I'd definitely run through the diagnostics to rule out temp sensor and solenoids. There's a good chance the cc unit is the problem, but easy and free to test other possible culprits before spending on a replacement...

Those little connector wires between the boards are a common weak point. It's a very tedious repair, and hardly any shops will take it on. Definitely test the temp sensors and solenoids first, as that's free and easy. If they check out, then the CC unit itself is the likely culprit.