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Discussion Starter · #1 ·
I have some questions about this system, if anyone can enlighten me. (I have a 94 RMW)
1) Is there a writeup in this forum, or elsewhere, as to how the extended readout functions work in this unit? Like, where does the climate control get tachometer and error code info? There is no tach info in the instrument cluster. And I certainly didn't see anything in the shop manual.
2) Are the control head units exactly the same 94/95/96? If not, what got improved? Is it worth getting a 96 in that case?
3) An actual problem or issue: In cold weather, my unit starts putting out really warm/hot air as soon as the engine is even somewhat warm. Very uncomfortable. After about 45 minutes, the airflow cools down. Until then, I end up turning the system on and off to modulate the cabin temperature to reasonable values. I think I saw in another thread that the system is supposed to compensate for engine warmup, but evidently none too well in my case. I would speculate that the cabin temperature sensor is just very slow in figuring out just how hot the circulating air is.
 

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The '96 C68 control head is probably different than the 94-95 one to take into account the OBD-2 of the PCM to be able to read the codes and other functions like the engine speed information. I plan on doing the C68 swap into my '95 Caprice SS/9C1 but will see if/when I get to it, have all the parts just need to wire everything up. - Peter
 

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Info for the codes in the display is in the Roadmaster section - scroll down a bit and see the stickys - useful stuff there.
 

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Discussion Starter · #4 ·
Let me rephrase one of my questions: Does the AC control head tap into the OBD port, so that you wouldn't really need an external code reader?
 

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Yes it reads data off of the main PCM data line that's at the OBD connector. It does not read ABS codes, for those you need a Tech1 or Tech2 scanner or other high end shop OBD scanner. - Peter
 
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