Crown Vic Park Kill & Relay Issues

acs680

Member
Nov 23, 2010
220
Tennessee
I had plans to kill the wigwags and revert the lightbar to mode 1 when the car was in park. I set up two relays on the car, one being for mode 3/wigwags and the other being mode 2. I wired the hot side of the relay to mode 1, and the ground side of the relay from fuse 1 on the Crown Vic that provides ground in park. I hooked the output from the Smartsiren to the common pin, and the NC pin to the lightbar mode/wig wag wire. When wiring was complete and I went to test it out, the starter would engage when turning on the slide switch to mode 1, thus enabling 12 volts to the relay. After testing the relays I was using, I noticed that 12+ was showing on the ground side as well. I opened up the relay, and realized that it had a feedback suppressor diode between the ground and positive pins. I removed the diode, thinking this was for sure the problem... Nope, the starter still cranked when the slide switch came on.


Am I missing something? Should positive be showing on the ground side of my relay with a multimeter? It makes since to me that the Crown Vic will start when 12+ is applied to fuse 1, but using pin 1 to provide a ground to my relay, should not being sending 12 volts back to the fuse...
 

axline

Member
Sep 6, 2012
34
Northern Michigan
See would be easier... However, I think I understand somewhat. Basically, you're using a fuse in the vehicles fuse box to provide ground to a relay to open the circuit to the WW? And instead of that happening, when you activate level 1, your vehicle starter cranks over.


My advice: Double check your relay wiring; 30-87a / 87(+12), 83/86 (control).


Best thing to do? Get away from the factory fuse box. Locate the park position sensor wire behind the dash and use that, or use the parking brake to drop the WW. The parking break housing generally has spade tabs on it that provide a clean ground when the break is applied.
 

C2Installs

Member
May 24, 2010
477
Tennessee
It's...complicated.


From Federal Signal Touchmaster Install Guide:


"DIGITAL CIRCUITRY WARNING


Some auto manufacturers have converted to Digital Park/Neutral reference signal.


Refer to Federal Signal Corporation Service Bulletin No 9.; Dated 11/03/04.


On these vehicles, the Park/Neutral position can only be monitored with a 5-volt reference signal.


Automobile manufacturers state that a 12 Volt or ground signal will result in damage to the vehicle starting system.


If installation of a UPKM-1 is to be utilized, please check with Unitrol regarding compatibility issues.


Federal Signal / Unitrol UPKM-2 is compliant with both digital and 12-volt systems."


From Ford 2009 CVPI Modifier's Guide, Section 3-8


"PARK/NEUTRAL Signal


NOTICE: Do not splice in this circuit with 12 volts or a ground signal as damage to the


vehicle starting system will occur.


Note: The PARK/NEUTRAL position signal can only be monitored with a 5-volt reference signal.


When the vehicle is in PARK or NEUTRAL, the reference voltage is grounded through the


starter relay control side (reference voltage drops to low). When the vehicle is not in PARK


or NEUTRAL, the circuit is open and the reference voltage remains high.


In the event that the police equipment to be installed requires a PARK/NEUTRAL signal, there is a


specific circuit that should be used. As illustrated in the Crown Victoria Wiring Diagram manual,


circuit 262 (BN/PK) is routed from the CJB fuse 1, to the digital transmission range sensor C167


Pin 12. Refer to Splices and Repairs under General Guidelines in Section 2 of this Guide."


Long story short, it won't work like you think it will work. This is a known issue with the CVPI, and Unitrol, as well as Whelen, IIRC, have interface modules for this purpose.
 

acs680

Member
Nov 23, 2010
220
Tennessee
What ever happened to simple....


Oh well, guess I'll put this project on hold until we get some interceptors with a park kill wire.


Thanks for the info!
 

Forum Statistics

Threads
53,968
Messages
449,817
Members
19,104
Latest member
airflores

About Us

  • Since 1997, eLightbars has been the premier venue for all things emergency warning equipment. Discussions, classified listings, pictures, videos, chat, & more! Our staff members strive to keep the forums organized and clutter-free. All of our offerings are free-of-charge with all costs offset by banner advertising. Premium offerings are available to improve your experience.

User Menu

Secure Browsing & Transactions

eLightbars.org uses SSL to secure all traffic between our server and your browsing device. All browsing and transactions within are secured by an SSL Certificate with high-strength encryption.