Help! Have a power lock issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

newmexicosaint · 01-16-2015, 11:42 PM

Okay folks, I am not much of a troubleshooter when it comes to wiring so I need your help...

My power locks on my 86 C10 are giving me trouble. When I hit lock both doors will lock. When I hit unlock I can hear something click under the dash but neither door unlocks nor makes any noise like the actuators are even trying. I assume the clicking I am hearing is a relay of some sort. I have changed BOTH lock switches and no improvement.

Any ideas?

Greenlee · 01-17-2015, 06:05 AM

There is a little box/relay looking deal screwed to the firewall. Its in the area above the gas peddle, and if i remember correctly it is not easy to see or get to. That's what you hear clicking.

When I was putting my truck back together, pushing the lock button made the clicking noise you are describing until I actually screwed that box to the firewall. I believe that is where the system gets its ground. The only other wire going from the power lock harness to the truck was a power wire that plugs into the fuse box. I would check that wire and all of the connections to the relay, and make sure it is still tightly screwed to the firewall. Also, check the wires at each switch. I suspect you are losing your ground, either because you have a loose wire somewhere or the screw came loose that holds the relay to the firewall.

**hatzie** · 01-17-2015, 07:44 AM

That box is an expensive special DPST relay package. The metal bracket and case is the ground for both coils.
The part # for 78-87 CK & RV trucks is 14056552 it's an obsolete part from GM and fairly expensive from other sources.
Get a meter out and verify that volts are going to the door lock solenoids.

newmexicosaint · 01-17-2015, 11:39 AM

Okay thanks guys. Will do. One last question...would that allow the locks to lock but only click when I try to unlock? Thanks

**hatzie** · 01-17-2015, 12:35 PM

If you hadn't replaced the switches I'd say it's them. I'd still test them both with a meter set on Ohms.

The big relay box is actually two relays with the coil ground on the metal case and a shared Common switch terminal. The wiring diagram shows the contacts parked. You can test the output right at the relay with a Meter set on Volts DC.

When either of the switches energize the Black/White wire one relay coil energizes and closes the circuit between the Orange/Black wire from the fuse panel the Tan wire to both lock motors. This is LOCK.

When either of the switches energize the Light Blue wire the other relay coil energizes and closes the circuit between the Orange/Black wire from the fuse panel to the Gray wire to both lock motors. This is UN-LOCK.

My guess is the UN-LOCK switch isn't closing inside the relay.
The Gray wire could have a break between the relay and the lock motors.
I'd check it with a meter first because a $100 Hail Mary is way too expensive to just throw parts at it.

tucsonjwt · 01-17-2015, 08:27 PM

In my case, it was just corroded lock rods in the doors - hanging up and causing the clicking sound with no lock action. I live in the dry desert but you can still get rust on upainted/uncoated surfaces.

I would pull the switches out and see if you have power going to them in both lock and unlock mode. If so, my next step would be to see if the power actually makes it to the actuators (requires pulling off the door panel.) If so, replace the actuators. Also, while you have the door panel off, sand off/clean/lube the lock rods and mechanism/links, etc.

The switches come out by using a flat blade screwdriver pushed in from the side behind the cover plate.

motornut · 01-18-2015, 09:47 AM

Quote:

Originally Posted by tucsonjwt

In my case, it was just corroded lock rods in the doors - hanging up and causing the clicking sound with no lock action. I live in the dry desert but you can still get rust on upainted/uncoated surfaces.

I would pull the switches out and see if you have power going to them in both lock and unlock mode. If so, my next step would be to see if the power actually makes it to the actuators (requires pulling off the door panel.) If so, replace the actuators. Also, while you have the door panel off, sand off/clean/lube the lock rods and mechanism/links, etc.

The switches come out by using a flat blade screwdriver pushed in from the side behind the cover plate.

see that all the time,with rotten door bottoms from salt here.

01-16-2015, 11:42 PM	#1
newmexicosaint Registered User Join Date: Apr 2012 Location: Clovis NM Posts: 30	Help! Have a power lock issue Okay folks, I am not much of a troubleshooter when it comes to wiring so I need your help... My power locks on my 86 C10 are giving me trouble. When I hit lock both doors will lock. When I hit unlock I can hear something click under the dash but neither door unlocks nor makes any noise like the actuators are even trying. I assume the clicking I am hearing is a relay of some sort. I have changed BOTH lock switches and no improvement. Any ideas?

01-17-2015, 06:05 AM	#2
Greenlee Registered User Join Date: Jun 2004 Location: El Lago, TX Posts: 1,668	Re: Help! Have a power lock issue There is a little box/relay looking deal screwed to the firewall. Its in the area above the gas peddle, and if i remember correctly it is not easy to see or get to. That's what you hear clicking. When I was putting my truck back together, pushing the lock button made the clicking noise you are describing until I actually screwed that box to the firewall. I believe that is where the system gets its ground. The only other wire going from the power lock harness to the truck was a power wire that plugs into the fuse box. I would check that wire and all of the connections to the relay, and make sure it is still tightly screwed to the firewall. Also, check the wires at each switch. I suspect you are losing your ground, either because you have a loose wire somewhere or the screw came loose that holds the relay to the firewall. Last edited by Greenlee; 01-17-2015 at 06:12 AM.

01-17-2015, 07:44 AM	#3
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: Help! Have a power lock issue That box is an expensive special DPST relay package. The metal bracket and case is the ground for both coils. The part # for 78-87 CK & RV trucks is 14056552 it's an obsolete part from GM and fairly expensive from other sources. Get a meter out and verify that volts are going to the door lock solenoids. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 01-17-2015 at 08:09 AM.

01-17-2015, 11:39 AM	#4
newmexicosaint Registered User Join Date: Apr 2012 Location: Clovis NM Posts: 30	Re: Help! Have a power lock issue Okay thanks guys. Will do. One last question...would that allow the locks to lock but only click when I try to unlock? Thanks

01-17-2015, 12:35 PM	#5
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: Help! Have a power lock issue If you hadn't replaced the switches I'd say it's them. I'd still test them both with a meter set on Ohms. The big relay box is actually two relays with the coil ground on the metal case and a shared Common switch terminal. The wiring diagram shows the contacts parked. You can test the output right at the relay with a Meter set on Volts DC. When either of the switches energize the Black/White wire one relay coil energizes and closes the circuit between the Orange/Black wire from the fuse panel the Tan wire to both lock motors. This is LOCK. When either of the switches energize the Light Blue wire the other relay coil energizes and closes the circuit between the Orange/Black wire from the fuse panel to the Gray wire to both lock motors. This is UN-LOCK. My guess is the UN-LOCK switch isn't closing inside the relay. The Gray wire could have a break between the relay and the lock motors. I'd check it with a meter first because a $100 Hail Mary is way too expensive to just throw parts at it. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.

01-17-2015, 08:27 PM	#6
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,189	Re: Help! Have a power lock issue In my case, it was just corroded lock rods in the doors - hanging up and causing the clicking sound with no lock action. I live in the dry desert but you can still get rust on upainted/uncoated surfaces. I would pull the switches out and see if you have power going to them in both lock and unlock mode. If so, my next step would be to see if the power actually makes it to the actuators (requires pulling off the door panel.) If so, replace the actuators. Also, while you have the door panel off, sand off/clean/lube the lock rods and mechanism/links, etc. The switches come out by using a flat blade screwdriver pushed in from the side behind the cover plate.



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