1997 chevy truck power locks

Actually, one more question other than the rated fuse size above.  As I was re-reading the manual for the Prestige APS-55C, I have a question on the Ignition 3 output.  I have seen 2 different data sheets for the 1997 Chevy 1/2 ton truck.  One says needs this output, the other says it doesn't.  Can anyone confirm whether this output is required on this truck?  The manual says to hook it to a relay.  Although it is describing a SPST relay, I have the bases covered after the discussions above.

Fuse size 20amps if 4 doors. TEST for third ignition, if so yes relay thus. 2nd ignition, branch to relay 86 Ground to 85 30amp constant 12V+ to 87 30 to third ignition.

dkeys23 wrote: Thanks once again for your help and insight. After drawing the schematic, I understand now with your help. I am a mechanical guy trying to survive in an electrical world. What size fuse should be used for the relay +12v?

A relay is electro-mechanical, so your half way there ;) I believe the factory fuse is 20A but there are a number of circuits fed by that fuse. I would not go bigger than 20A, I would err on the safe side and use 10A.

dkeys23 wrote: Actually, one more question other than the rated fuse size above.  As I was re-reading the manual for the Prestige APS-55C, I have a question on the Ignition 3 output.  I have seen 2 different data sheets for the 1997 Chevy 1/2 ton truck.  One says needs this output, the other says it doesn't.  Can anyone confirm whether this output is required on this truck?  The manual says to hook it to a relay.  Although it is describing a SPST relay, I have the bases covered after the discussions above.

As a general rule for myself, any GM truck that I work on from 1995 on that has multiple ignition wires, I power all of them to avoid setting a DTC which may put the transmission in limp mode. Not doing so can cause more headaches and wasted time and money than connecting these wires. Your 3rd ignition is a negative output so you must use a relay. Just wire the relay as follows: 30 = 3rd ignition wire of vehicle 87 = constant 12v 87a = not needed, get rid of the wire or insulate 85 = 3rd ignition output of r/s system 86 = constant 12vThis information is provided only as a reference.

All circuits should be verified with a digital multi-meter prior to making any connections.

OK guys.  I finally got around to installing the remote start / keyless entry unit.  Everything went well on the remote start.  It functions as intended.  I wired up the 2 relays for the door locks and ran into an issue.  The doors will unlock, but the fuse blows when I push the lock button.  I will attempt to describe how I have it wired. 

I have both relays pins 86 and 87 to a constant 12+ (all on the same source) fused with a 10A fuse.  I have cut the LT blue lock wire at the switch (the harness was in the inner cowl and I couldn't access it so I ran a 4 wire lead into the door).  Either end of this wire is connected to the 87a and 30 pins on the relay.  The 85 pin is going to the keyless entry module.  I have cut the White unlock wire at the switch and wired to the 87a and 30 pins of the other relay.  As I'm typing I can't confirm which end is 87a and which is 30, but as  I refer to a schematic, I can't see how that would make a difference.

As a check, I powered a continuity testor (to check for ground) and confirmed that the lt blue wire is ground until the moment the lock button is hit and the white wire has the same ground except when the unlock button is hit. 

Does anyone have any ideas?  Could this setup need a diode?  Any help would be appreciated.

Thank you.

Change 30 and 87a around on the lock relay. Because of the way the relay works 87a MUST go to the switch or car side and 30 MUST go to the motor (actuator) side. If there are 2 locks I would go 15 amps, with 4 (i.e. side and or tailgate locks) I would go to a 20 amp fuse.

Thank you for the response.  That is exactly what the issue was and has been corrected.  Can you please take a minute to explain to me why this direction matters? 

 If I look at the layout of a relay, the normally closed circuit supplied 12+ from 87 to 30. When I press the transmitter lock button, it supplies a ground to the negative side of the relay coil (85 & 86) which energizes the coil to swtich the poutput from 87 to 87a.  This results in a closed circuit from 87a to 30.  I guess I don't see how polarity is an issue.  If someone could explain, that would be great.

Thanks to everyone that has helped with direction and/or advice.

Actually 87a is the normally closed circuit, 30 is the common and 87 is normally open, thus 30 continuous to 87a becomes 30 continuous to 87 when the coil is activated. Polarity is only relevant across the coil, the ISO or SI labelling applies to all the terminals on a modern car just as the icons on your gauges are the same such as fuel, temperature, parking brake whether your vehicle was made in Kazakhstan or Detroit (Blazers are made on Kz!) or Tokyo. The convention makes 85 the neg side and 86 the pos side. This is relevant for 1 reason. Some relays have built in diodes. The reason being that when the supply to the coil shuts down you get an "onrush" voltage spike. This can feed back to delicate chip or transistor circuitry and ruin it such as your alarm and R/S, been there and done that. The diode prevent this, in fact finally DEI recommend it with their 5901/2 series.