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Username Post: Heaater/AC control unit        (Topic#351115)
Posts: 4

Reg: 05-14-18
05-14-18 08:56 PM - Post#2733997    

All the indicators are constantly flashing. The system seems to work accordingly. I tried anothe heater/AC control unit and got the same result. Where should I be looking to find a problem?

Frequent Contributor
Posts: 1219

Age: 59
Loc: Murphy N.C.
Reg: 01-25-14
05-15-18 03:48 AM - Post#2734001    
    In response to william1180

Clean the contacts on the unit and plug with contact cleaner spray.

Posts: 4

Reg: 05-14-18
05-15-18 08:12 AM - Post#2734024    
    In response to junkman104

Good idea! I tried this and no change.
When ignition is turned on all seems normal. A few moments later and the selected position indicators all start to flash. All functions seem to work. Turning the key off and on again shows a normal condition,few moments later abnormal condition.Strange it did this with a replacement unit too.

Valued Contributor
Posts: 3992
Age: 35
Loc: wv
Reg: 08-29-12
05-15-18 10:34 AM - Post#2734034    
    In response to william1180

If it is the temperature arrows, the actuator is bad.


'88 Chevy K3500, aluminum head roller cam 511inĀ³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

Posts: 4

Reg: 05-14-18
05-15-18 10:24 PM - Post#2734078    
    In response to bowtie44s

Thanks Jeff, I'll check this . Also the direction of air flow does the same thing. I can change both temperature and direction of air flow. Just the arrows on both flashing.Although I hadn't actually checked the airflow movement to verify where it was coming out.I'll check that next.

Senior Member
Posts: 2352
Loc: MA
Reg: 04-06-03
05-16-18 04:03 AM - Post#2734080    
    In response to william1180

Possibly a blend door is not operating/opening FULLY. My 94 K Blazer has been doing the "flash dance" for years when I put it to "Defrost" still defrosts the windshield so I just ignore it.

I even have a brand new AC/Heat dash control unit that I do not need....hint hint

Posts: 4

Reg: 05-14-18
05-17-18 09:50 PM - Post#2734224    
    In response to scrambldcj8

Thanks for the tip on the blend door activity.I'll be checking that in a couple of days.Some other tips I've received to be checked out also.
Don't need a new unit as I also have a spare now that I ordered last week. It also had the same results. so it's obviously not the control unit.

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