89 Scorpio Temp Dash error code? No Heat!

Hey all... after having recently replaced a power transistor to get what I thought was a blown blower ($$$$) I thought that my winter heat woes were solved, now that the air was back to blowing... But when I
start it up, the temp display works fine, I can adjust the temp no prob. Minutes later I see the temp display go from what I set it to, to flashing "08" then the original temp I set, then "08" again! And I hear the vent door motors start actuating, but NO heat comes out. Just ambient air. I've tried looking everywhere for what this "08" means but I cannot find any info. The guy that sold my Pop's the car told us it was a temp sensor, namely the one in the main vent... so I disassembled the whole dash, found it and tested it's resistance with a voltmeter. It increased /decreased resistance as it should when I would blow warmer/colder air on it. So I know it's working fine. I also tested the other 2 sensors; the one on the inside of the car and the one right above the power transistor I replaced. Both or should I say all 3 are working fine! Does anyone have any suggestions? I REALLY need HEAT! Thanks.
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Maybe you should check the resistance of the sensors right at the circuit board if you can. There might be a bad connection. Or you count try replacing the sensor wires at the circuit board with a suitable pot, and see if the board responds. Fred

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Fred, Thanks for responding! Hrmm I would have done that orginally but it was getting cold and dark, that and I didn't think of it at the time. The problem is getting to the circuit board - there's a HUGE amont of tubing and wires etc that make 1) finding it a problem and 2) once found, getting to it... argh, I was hoping that it would have been as simply as fixing a lose wire or something like that, but geesh, I'm going to have to dismantle the whole dash, not just the top to get to the circuit board...argh, well thanks for the advice/suggestion!
BTW - When you said "with a suitable pot" I assume you mean Potentiometer? And if so, what resistance range? If I recall right the res on the thermistors was ~4.7K
Thanks, -J
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Hi Jay
Yes, a Potentiometer! Sorry about that. Being in electronics so long does that. Try a 10 k pot. That should be fine. connect the center and one end together and that's one lead, and the free end of the pot is the other lead. You might also check if you get any voltage across the sensor leads with them disconnected. You should probably get some voltage reading of some sort. No voltage there probably means a bad connection somewhere or something blown on the circuit board.
Fred

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Fred, Hello again, darn... just what I need- a potential blown circuit board or something that is going to be VERY hard to replace, and even more hard to find a replacement... Dang this merkur! How ridiculous, the heat doesn't work b/c of some stupid censor/board... I could have went american and least the heat would be on the hottest setting if a censor was messed up Vs NO heat at all... Well thanks again!
-J
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