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Old 08-18-2011, 05:02 PM   #1
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Brake "sense" for trailer brake controller??

Question for those who are towing trailers and have installed a brake controller - where did you find the brake sense for the controller - what the controller instructions calls the cold side of the stoplight switch?
(Trying to wire a Tekonsha Primus IQ controller.)

David Horn, TX; 2014 40ft Phaeton QTH; 2014 Mazda CX5; 2013 Can-AM Spyder RT-S on TandemTow trailer; Traveling with Ringo (an English Cocker)
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Old 08-18-2011, 05:25 PM   #2
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I think what you are asking is where is the lead that the brake controller is wired to in order to sense the application of the tow vehicle's brakes, right?

It is the cold lead on the brake pedal switch, the one that you would NOT see 12VDC to ground, until the brake is applied and the switch makes across. Under the dash, attached to the brake pedal on mine.

Get a voltmeter, and find which side of the switch only has power when the pedal is engaged. That's your brake sense.

When the brake controller sees this lead got hot (12VDC), it applies power, from a fused supply, to the trailer brake circuit, normally attenuated by a adjustment/sensitivity wheel.

hope that helps

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sway & trac bars, Koni FSDs and SafeT+
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Old 08-18-2011, 10:39 PM   #3
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Be aware that a relay is usually needed on Alpines when using the brake sense wire to signal. Cheap standard relay from NAPA, Pep Boys, etc. I'm not sure if the Vansco setup changes that. Mine is pre-Vansco (luckily ).
2003 Alpine 40FDTS (400HP)
Long Beach, CA
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Old 08-18-2011, 10:58 PM   #4
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Jack, alpines have a hydroboost brake system over hydraulic. So finding the brake cold side is not like a standard car system. Additonally, alpines after 04-05 I think have vansco electrical management system, so this makes it more complicated to wire in the controller. We appreciate your comments.

TP - Sent you an e-mail about LED's, did you get it?

David, TP is correct, you will need to install a relay but not sure where. More information is needed from folks who have done it.
Monty & Janet - 2007 Alpine APEX 40 MDTS
S/N - 75715 - Retired - Master Certified RV Tech
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Old 08-19-2011, 12:05 AM   #5
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Here's a thread, and
posts 6, 8 & 12 in this thread
have the pertinent discussion for an easy, clean & professional install.
David- alert your tech to these links; i described this to him this a.m., but not sure the technique was as clear as in those posts.
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Alpine: The Ultimate DIY'er Project
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Old 08-19-2011, 09:29 AM   #6
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Thanks Mike and Monty for all your help. Info passed on to Chris.
David Horn, TX; 2014 40ft Phaeton QTH; 2014 Mazda CX5; 2013 Can-AM Spyder RT-S on TandemTow trailer; Traveling with Ringo (an English Cocker)
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Old 08-19-2011, 10:22 AM   #7
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In most vehicles the stop light switch is under the dash, look for a pair of wires going to a plunger switch that is impacted by the brake pedal arm when it's not depressed.

(That is the switch is realased by pressing on the pedal)

Use a test lamp to determine which is the "Cold side" (with the key on, and on many vehicles even if it's off, the "HOT" side will light the lamp, the cold will not unless you press the pedal.

On some vehicles it may be a pressure operated switch but I've not seen one like that since... well... A long time.

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