CHRIS COVE

My passenger door will not unlock by either switch or fob. I swaped the drivers DCM to the passenger door and it worked fine, so I've eliminated an acuator or wiring harness problem. I replaced the middle relay and the problem continues. Which other relay(s) should I replace.

Thank you in advance!

lucky131969

How did you determine that relay was bad?

CHRIS COVE

A post I read recently said the bottom was the unlock relay and middle was the lock relay. I tried to just feel the relay when it switches but its hard to determine which one is switching. I just replaced the bottom one. Still doesn't work. I have one more new relay but I want to make sure before proceeding.

CHRIS COVE

This is the post I read:

http://www.ronjpics.com/Corvettestuff.htm#DCM

lucky131969

You don't have to guess. For comparison, you can feel relays in the DCM that works, and determine which ones click when the switch is actuated. Also, you can use a meter, and determine what relays are working, and which ones are not.

CHRIS COVE

I did check with a meter and the center relay wasn't switching but after replacing with a new one it's still not working. I'm wondering if another relay needs to be replaced also. What do the other two relays do. The top one of the three and the one to the side. I might just be that the new middle one is bad. It ohmed out ok on the bench.

CHRIS COVE

I'm looking at the schematics and the other relays appear to be for door key switch signal and door ajar switch signal. I might have just installed a new middle relay that's bad. Other than that, the schematic makes no sense to me and I'm wondering if anyone else that has had this problem could tell me if there are any other relays I need to replace.

lucky131969

Did you also ensure the relay in question had a voltage input, and good ground on the coil side? If the aforementioned were not good, they the relay would not work.....so you may have replaced a good relay.....not installed a bad one.

CHRIS COVE

Yes Lucky thanks. "I had" 11.6V to the relays but now I think I just blew a fuse. I arced my meter now I have now power to any. I'll be fixing that now.

CHRIS COVE

ok back in business. I replaced the fuse and just noticed the Body Control Fuse is missing. I put a new one in to see if that made a difference and it didn't.

CHRIS COVE

Thanks for the replies Lucky. It must be something in the board but after replacing two relay's and a blown fuse I think it's time for another board. Anyone selling a used Board?

lucky131969

You did not have a blown fuse problem before, right? You connected the drivers DCM to the passenger side, and it worked fine....again...no blown fuse. You replace relays on the passenger side DCM, and now you have a problem blowing fuses. If I have this sequence correct, it sounds like you may have damaged something, or have a solder bridge somewhere.

CHRIS COVE

Correct, I swaped the drivers DCM to the passenger side and everything worked fine. I only just blew the fuse on the passenger DCM when I was checking the voltage, I arced between two points but only after getting a good voltage reading, my bad.
At this point I have replaced two relays on the bad passenger board. The middle one and lower one but the unlock function still doesn't work.

seoulbrooks

You need to make sure you have a ground on pin B of the DM from the lock actuator relay. When unlocking the 12vdc comes from the Unlock relay on pin D of the DM and the ground is applied on Pin B from the Lock relay. Just the reverse for locking. You know the wiring is good to the Motor because it worked with different module. I would suspect you are missing the ground from the Lock Relay de-energized contacts. The Door Module has two relays for lock and unlock, both apply a ground or 12vdc through the contacts to the motor. The current flow controls direction of the motor. With no unlock/lock command there should be a ground at both pins B & D of the Door Module. A quick way to check would be to apply an external ground to pin B and then hit your unlock. Also, make sure you do not have the passenger door set for needing two unlock commands. Double click the FOB unlock..... Good luck!

Go here for a picture of the module and relay locations...http://www.ronjpics.com/Corvettestuff.htm#DCM

Cratecruncher

Just to make it even more confusing: Remember the door lock circuit is caried on two different harnesses. Lock is "B" on harness C2, while unlock is "D" on harness C3! Also, if you're still uncertain whether you've replaced the correct relay, try tracing the pin on the board corresponding to the connector back to a relay pin.

My locks still work fine. My RH window doesn't go down so I'm interested in this nest of relays too! I think the other ones control mirror and window motor but not sure until I pull it out and trace the board. It would be nice to have actual circuit diagrams instead of "wiring charts".
Crate

C5at57

PM sent.

LoneStarFRC

FWIW, there is/are a couple guys on that big auction site offering rebuilt DCMs for like $65.00 or so.

HTH

CHRIS COVE

Great points above, Thanks. I have power at points B and D but haven't checked to ground. I'll do that and let you know what I find.

CHRIS COVE

Where is this big auction site? Is it in this forum? Thanks. I'm not so good at troubleshooting circuit boards and can't really follow the schematics.

C5at57

I sent you a PM, I have one I can sell you for $60.