Porsche 928 HVAC Controller Repair

How to repair a common Porsche 928 HVAC controller unit failure, which leads to loss of AC function. Shows typical controller internal relay failure symptoms and as-found condition. Shows replacement with a more robust relay to restore full controller function. The factory installed unit is made by Behr. Its internal relay for the AC compressor clutch is small, rated for 2.5A. The AC compressor clutch that it supplies can draw more. It is common to see these burn out leading to puzzling intermittent failure, or full failure of air conditioning function.
While not shown in the video, consider adding a protective fuse inline with the controller power.
More detail on unit removal and installation, without damaging anything, can be found here: • Porsche 928 HVAC Contr...
Credits to Dwayne and others in the 928 community for repair methods.

[@noahblitzy3244]

Really appreciate this level of Patience!

[@markfranke8326]

Thanks for watching! The repair is fairly easy once you know how it all goes together.

[@OB928]

Impressive diagnosis and repair. Based on my electrical expertise, I’d probably just have to go without A/C. Fortunately mine works.

[@markfranke8326]

Thanks, and thanks for watching! That relay is a common failure point. Hope the video can help should anyone encounter it!

[@petero2778]

Great video. I just did this a few months back on both my 928’s and so happy to A/C working again.

[@markfranke8326]

Thanks Peter! Great to hear.. 928 A/C blowing cold makes a huge difference doesn't it!

[@upssidep9283]

Fantastic job! Thanks for sharing!

[@markfranke8326]

Thanks for watching!

[@kirbyhade2961]

Thank you for this!

[@markfranke8326]

My pleasure!

[@cleaningrestoring4809]

Nicely done!

[@markfranke8326]

Thanks for watching! Super nice looking '84 928 that you have in your vids!

[@claygraner4450]

Isn't there a higher amp rated relay that fits back into the OEM board? I was thinking there is.

[@markfranke8326]

I think you could find a board mount solution. The reason I opted for externally mounting it is for easier future maintenance, and it keeps relay and heat away from the board.

[@claygraner4450]

@@markfranke8326 Agree. Simple, inexpensive, easy to maintain. Great solution.

[@royasm8964]

I have hunted this part number all over and cannot find it. It is discontinued. Do you know of another part number that will substitute? Many thanks for the great video!

[@markfranke8326]

Thanks Roy, glad you like the video. The relay is a basic general purpose DPDT 12VDC relay. The TE relay in video appears NLA. On the Digikey website a substitute part is listed, K10P-11D15-12. Haven’t tried it but looks similarly robust, industrial, rated for 15A. Amazon sells NTE brand 10A R14 series and Radio Shack has something similar. There are lots of relay options. The compressor may draw up to 3A, so suggest that as a min rating.

[@thomasbainbridge6811]

@@markfranke8326 Mark,I'am considering inserting a 3amp to 5amp fuse link(per your suggestion) between either the controller sw/relay and the electromagnetic clutch relay towards the a/c compressor or between the controller sw/relay and the 7amp fuse located in the main relay/fuse box under dash passenger side for additional protection since the new controller sw/relay is rated at 10amp 12 vdc.Your thoughts would be helpful.Tom

[@markfranke8326]

@@thomasbainbridge6811 Hi Thomas. It is the compressor current that will task the relay. I would add the fuse there. In the original configuration, one might speculate that the underrated relay, whether by design or happenstance, served a dual function as overcurrent protection, in that it would fail early on fault and excessive current demand.

[@thomasbainbridge6811]

What is the brand and where can the suction tool for bulk solder removal be obtainedThanks.Great fob!

[@markfranke8326]

Thanks for watching! The desolder tool shown in the video is unbranded. I would not overthink this tool too much. If you go onto Amazon and search for "solder sucker" you can find a variety, at reasonable price, with good reviews.

[@shark6192]

Dude this is nutz I hear people on meth can do this stuff you lost me after you pulled the stereo

[@markfranke8326]

lol

[@glennmacdermod2599]

Awesome video, great job! Can I send you my controller 😬 my S4 is doing the same thing!