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I've recently acquired a 2004 Buick Rendezvous, which has an aftermarket remote start unit installed (Excalibur RS-450-EDP+). Unfortunately, the previous owner did not hook up the remote entry feature.

After some initial research, it appeared that a separate unit was required to connect between the remote start and the vehicle. After more research, it appears that maybe a simple resistor is all that's required.

According to the documentation(PDF), the remote start unit wiring looks like this.

Remote Start Unit Wiring
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According to this document (PDF), Lock is a negative trigger through a 470 ohm resistor, and unlock is a straight negative trigger.

Vehicle Wiring
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Can I simply install a 470 ohm resistor on the Green wire from the remote start unit. Then combine the other end of the resistor, with the Blue wire from the remote start, and the Red/Black wire in the vehicle?

Proposed Wiring
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Or do I have to purchase an additional unit?

UPDATE:

These Installation Instructions (PDF) seem to agree.

Single Wire (Dual Voltage): Late model Chrysler/Dodge/Plymouth Vehicles, some 2000-UP GM Cars Dual Voltage systems have lock/unlock switches that send varying levels of Positive voltage OR Negative ground current to the SAME wire for both lock and unlock. When the vehicle’s Body Computer Module (BCM) or door lock module senses different voltages on this wire, the system will either lock or unlock. Single wire door lock systems require resistors.

Chart showing resistor size

And even provide a diagram similar to the one I've created.

One Wire Resistor Door Locks Diagram
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  • And no one suggested using two diodes
    – JayD
    Commented Feb 27, 2017 at 16:38

3 Answers 3

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I assume that at this point you've already figured it out, or gone another route.

Buuut for anybody that's still interested, this will work as described in this photo from above: Diagram From Above

The negative outputs (blue and green) are simply connected to ground when the corresponding relay (unlock and lock) inside the remote start is activated. The unit labeled "Factory Door Lock Module" is either looking for a full negative signal, provided by the un-resisted blue wire, or a resistance (470 ohms in this case) from the green wire.

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Unless you have a safe and working example to go by, the smart money is to obtain and use the Excalibur's accessory unit. If the installation merely required a 470 ohm resister to extend its functionallity it is a safe bet the manufacturers would have incorporated it already.

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  • I disagree. The manufacturer uses the most common standard. It can't compensate for all the oddballs, and still be economically viable. The add-on unit is an attempt at compensating for the non-standard vehicles, and as such has an additional cost associated with it.
    – Tester101
    Commented Dec 4, 2013 at 15:40
  • Manufacturers do not build their equipment along common standards, but do have meet certain criteria with what they do build and how they build them. The pdf you have linked into is for your specific vehicle. A differant vehicle would have a differant pdf. If your vehicle requires an extra, then that would only go to show the variations that there are from implementation to implementation.
    – Allan Osborne
    Commented Dec 4, 2013 at 17:44
  • What I'm saying, is that vehicle manufacturers tend to have a specific way they like to do things. Aftermarket starter manufacturers take advantage of that, by building their units based on the most common practices. If a vehicle manufacturer does something odd, the starter manufacturer likely can't account for that. So to say that because the starter manufacturer hasn't included the resistor, means that a simple resistor cannot be the solution, is just wrong.
    – Tester101
    Commented Dec 4, 2013 at 18:01
  • We are starting to digress a little from the original question. The question asked is how feasible is it to bridge two wires of a circuit of a unit whose internal circuitry is not fully represented. The mentioned unit becoming an integral part of vehicles wiring and Body Control Module, without knowing if has been done before. All in the light of there being an available second unit to enable the required function. My advice as before would be to use the second unit. You can always try the fuse work around but be aware it could all go wrong on you.
    – Allan Osborne
    Commented Dec 4, 2013 at 21:40
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There is that language in Exhibit 2:

Relays must be used

...which indicates to me that you shouldn't tie the two outputs together (even through a resistor), but should use those two outputs to drive a pair of relays which will connect to the car's wiring.

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