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Discussion Starter · #1 ·
Okay so I have been trying to chase down a parasitic draw on my batt. Runs dead every night. Finally discovered after lots of diagnosis with my DMM that when ignition is turned off the after run fan is staying on long enough that the battery is being drained below 12v before the fan shuts off. The cool down time seems much longer than it did in the past. Water pump, thermostat were recently replaced and coolant flush.

What controls the length of time this fan stays on and what is the norm for after run cooling time?

Any common issues that would allow this fan to stay on longer than normal?
 

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Discussion Starter · #4 ·
psychorallyfreak said:
Perhaps the after-run temp sensor is borked?
After reading through SJM which I should have done in the first place :slap: Its starting to sound like a bad relay... Ill update this post when i find out. They list a few test to go through before I go any further.

I am curious though if anyone has happened to bypass this system all together and have run a manual on/off/auto switch. Or maybe adding more wires to the mess is tom foolery.
 

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Discussion Starter · #5 ·
"The after-run relay will limit the time (8-10 minutes) the low speed fan and turbo cooling pump will run, to avoid running down the battery if the temp switch should fail."
 

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Discussion Starter · #6 ·
Or a combo of both
 

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U could wire in a 5 terminal relay with a NO and NC circuit and a manual timer but that would probably run u around $60 just for the relay. I've run through those tests myself before. It's not bad so it better off sticking to the stock system. Time to get ur battery checked too.
 

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Discussion Starter · #8 ·
88a5tq said:
U could wire in a 5 terminal relay with a NO and NC circuit and a manual timer but that would probably run u around $60 just for the relay. I've run through those tests myself before. It's not bad so it better off sticking to the stock system. Time to get ur battery checked too.
10-4, Battery just got a checkup yesterday, all good! Gets to sit on the charger in the meantime...
 

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Discussion Starter · #9 ·
How much resistance should the after run temp sensor have when cold vs. hot? I cant seem to locate too much info.
 

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The afterrun temperature sensor is just a switch so infinite resistance when cold, no resistance when hot.
 

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Discussion Starter · #11 ·
Hmm so Relay clicks and shows continuity, check, temp switch clicks during bench test and shows infinite resistance when cold and 0.03 ohms when hot so close to no resistance but close enough right? The relay is supposed to keep the fan from running down the battery if the temp switch fails. Both test okay. Any suggestions for what to look at next?

Would either just fail or do they slowly wear out over time?
 

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My guess is your battery needs replacing. How old is it? Or you have a draw somewhere else...
 

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The afterrun relay is not really a relay at all it's more of a control unit. It's brown in color. If it's bad it will cause the fan/pump to run constantly with the car off.
 

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Discussion Starter · #14 ·
"My guess is your battery needs replacing. How old is it? Or you have a draw somewhere else..."

Battery is less than a year old and has been load tested at two separate locations. Passed both times. I performed a parasitic draw test and I come back with .11ma of draw on the system b4 and after after run fan not enough to drain the battery overnight. Pulled fuses and found the .11ma draw is coming from the clock. Seems normal enough.

Just replaced the alternator to be on the safe side but the same condition still exists. During road test I can see the alt. is charging the battery between 13v - 14v.

With DMM still hooked up when parked and motor off the battery discharges normally but stabilizes above 12.5v. Then after run fan kicks about 2 mins after shutdown on and I can watch the volts trickle on the DMM from > 12.5v to < 11 volts.

Fishy fishy.. Ill keep plugging away. This systems seem pretty straightforward but has me about to pull my hair out.
 

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Discussion Starter · #15 ·
yodasfro said:
The afterrun relay is not really a relay at all it's more of a control unit. It's brown in color. If it's bad it will cause the fan/pump to run constantly with the car off.
The Bentley is not clear on this system or maybe I'm misinterpreting the wording in the book, I'm assuming it is the 500w fan relay to the left under the steering column according to the sticker on the pop out access to the relay. I unplugged it an fan turned off lol :dur:
 

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Weird. So are you experiencing the same thing if you unplug the 2 after run pump sensor wires and insulate them with electrical tape so the after run pump won't come on? That's what I'd try. Then it will either confirm or deny the after run pump.
 

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Discussion Starter · #17 ·
rogermoz said:
Weird. So are you experiencing the same thing if you unplug the 2 after run pump sensor wires and insulate them with electrical tape so the after run pump won't come on? That's what I'd try. Then it will either confirm or deny the after run pump.
I can unplug the two wires from the thermoswitch and insulate them to avoid shorting to the block. When unplugged fan turns off. Touch the two wires to each other the fan will continue to run untill wires are disconnected.
 

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But if you just unplug them and insulate them does your battery voltage do the same thing?
 

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AUDIschwagon said:
The Bentley is not clear on this system or maybe I'm misinterpreting the wording in the book, I'm assuming it is the 500w fan relay to the left under the steering column according to the sticker on the pop out access to the relay. I unplugged it an fan turned off lol :dur:
As long as it was the brown relay you got the right one.
 
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