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Join Date: Oct 2006
Location: MYR S.C.
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Auto heat part deux.
I did a thread many years ago about the auto heat and how it works and what goes wrong. I repaired my ckt board once and it went bad again. Then I ordered a new digital board and it just burned up so I am done with it.
I have thought for a while about just a switch to turn on the heat and keep it original looking without spending a fortune so now I am finally doing it Biggest problem with this is where to mount the switch. I finally decided on the left side on the removable cover. I have always left the right cover off so I can feel the arm move and how much it moves. So I will leave it that way. All you need on the ckt board are the two diodes That are part of the circuit that turns off power to the motor when the arm reaches its limit. The fan will still have low med and hi speed controlled by the rotary dial. Low is 1-7. Med is 8-9 and hi is def. I used a DPDT on-off-on rocker switch. ($26). Wire the 4 outside terminals in an “X”. Two terminals on one end goto the motor. The two middle terminals go to 12v and ground. All the wires go to the ckt board. I will show you where. Later I cut everything off the board except the two diodes. I also had to cut the ckt board in half just past the bracket that holds the ckt board in place I also removed the connectors and wiring that goto the temp sensors and I cut the part of the board off that held the two connectors so the switch would fit. The way it will be wired up I can have heat without the fans being turned on.
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86 930 94kmiles [_  _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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Yesterday, 04:41 PM
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86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold Last edited by T77911S; Yesterday at 04:46 PM.. |
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Yesterday, 04:42 PM
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Location: MYR S.C.
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 Ckt board is cut in half 
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86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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Yesterday, 04:48 PM
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Location: MYR S.C.
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 The temp connectors are cut off along with the wires and terminals that goto the variable resistor. That’s not needed anymore  It’s still a tight fit  How I laid out the lines to cut the hole for the switch. Then I put the cover back on and marked the cover and used a cutoff wheel on a dremel.
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86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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Yesterday, 04:53 PM
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A little bit about how it works.
 The switch on the right is for low speed fan. The two big wires. The other two wires are for the limiter for the motor. This is the switch that goes bad All the time but there is a “spare”. The switch under it is the same. Just swap them out. I think when this switch goes bad the fans run all the time. The switch on the left is the limit switch for when the heat is turned on.  The switch at 10 o’clock is no longer used but it just provided a ground for the ckt that acts like a temp control. The switch at 8 o’clock turns the fan on to medium The switch at 3 o’clock is the hi speed switch. It provides a ground for a separate relay just for hi speed.
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86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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Yesterday, 05:00 PM
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Location: MYR S.C.
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Tomorrow I will finish it.
I need to get power to the switch and trim up the wires. I have to figure out my connections since I got the switch close to the reostat. You have to be careful of the emergency brake. I will put the 12v on the upper terminal away from the brake. I should be able to operate the rocker switch with my thumb. I hope ����
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86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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Yesterday, 05:07 PM
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great idea and very clean job....
Ivan
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1985 911 with original 502 191 miles...808 198 km "The difference between genius and stupidity is that, genius has its limits". Albert Einstein. |
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Today, 01:34 AM
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