John V

Hi folks,

I have my dash out for recovering and am going through my HVAC controls because don't seem to be working properly. I replaced the heater valve (was missing completely) but the vacuum line going to it doesn't seem to function,(never has vacuum present). I think I have some other problems as well because I can;t get any heat and I would thing that wiht no heat valve, that would be all that I got. It seems that I'm missing the outside temp sensor and alternator hose assembly. I'm not certain but my reading suggests that this sensor (and the internal one)is linked to the mixing flap. I need to start working through each defect to try to get everything fixed prior to re-installing the dash.

I've read that these sensors are simple thermistors but haven't been able to find any specs or test proceedures for each of the two in the circuit. Does anyone know what the values vs. temperature and rates are and how to test the circuit inputs and resulting flap actuations? Would I be better off just getting a new or used unit and seeing if that would fix all the problems? I'm not a big fan of replace and try diagnostics but it seems this system is pretty involved and the manual doesn't cover any significant diagnostic proceedures.

Thanks in advance.

jim morehouse

John,
I thought I'd saved a post that Wally Plumley had on this but can't find it. The one thing I did find was some measurements a lister took on his outside temp sensor:
450 ohms at 80F
1200 ohms after 5 min in freezer
300 ohms after hitting it w a hair drier

If I find more I'll post again.
Jim

jim morehouse

John,
If you haven't already, check out some of the climate control tips on Greg Nichol's tips site http://www.nichols.nu/tips.htm

Jim

Jerry 87 928S4

John, I have seen the manual you need. I no longer have a copy but someone who reads these posts now has.

John V

Thanks for all the info guys,

I think I have enough info to be dangerous now.