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(Very Strange) Central Locking Issues

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
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Volvebaker
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Year and Model: 1993 850 GLT
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(Very Strange) Central Locking Issues

Post by Volvebaker » Wed Dec 05, 2018 11:15 am

I've scoured the numerous threads related to Central Locking issues but I haven't come across any quite like the situation I'm dealing with, so I figured I'd detail it here and maybe get some new leads.

My central locking has always functioned perfectly! Lock or unlock the driver, passenger, or trunk and all other doors and gas would lock or unlock. They also functioned properly with the remote key fob. Then, the rear passenger side fender was dented in, right around where the actuator for the gas door sits, and the central locking suddenly stopped working.

I went to the salvage yard and pulled 2 replacement central locking relays as well as a gas door actuator (out of suspicion the dent location may had played some role in the malfunctioning. Now, stick with me, cause here's where it gets strange:

I replaced the gas door actuator with the salvaged replacement and it now responds correctly to the lock/unlocking of driver, passenger, and trunk however, all other locks are still not responding properly, ONLY the gas door. In addition, the gas door (again only gas door) will unlock with the key fob but will not lock.

So, I tried switching out the relay with the salvaged ones and it gets stranger. With the replacement relays, the gas door no longer responds to the lock/unlocking of driver, passenger, or trunk but it now WILL respond to both the locking AND unlocking using the key fob, but again, only the gas door. Both of the salvaged relays cause this and when I reinstall the original it is back to previously detailed situation.

Would like to get my central locking back to working properly, but not really sure where to begin with this strange situation.

Thanks!

P.S. 1993 Volvo 850 GLT

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jvl
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Re: (Very Strange) Central Locking Issues

Post by jvl » Wed Dec 05, 2018 1:32 pm

Hmmm, I've no experience with 850's.
But, in general electrotechnical terms, this sounds to me like your replacement actuators might either have a different pinout/and or a different resistance compared to the original one. This might cause this erratic behaviour?
Are the part numbers identical?

It could be so that the replacement actuator has also gone bad.

Another option could be that the actual fault is with your wiring loom (broken/stripped wire somewhere?) and that it's just a coincidence that one setup works and the other doesn't.

Sorry for not offering more specific guidance.
Good luck, hope you'll find the cause soon.

Joost
1999 V70XC. Stock, except.... I like tinkering:
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Volvebaker
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Re: (Very Strange) Central Locking Issues

Post by Volvebaker » Wed Dec 05, 2018 2:40 pm

Did you mean the replacement relays may be different? As that's what I got two of at the salvage yard but only one actuator just for the gas door. In any case the relays are both the exact same as my original from what I can tell (same part number and pinouts) just a slightly lighter color.

I considered the possibility that when fender was dented around the gas door actuator and harness that it possibly cause a sort of surgery through the system (I have no real electrical knowledge) and fried all the actuators? Which is possibly why the replacement gas door actuator works but all the others remain not functioning.

However, I would assume had this been the case it would have blown the use or the relay but that was not the case as relay appears to still be sending the signal and fuse isn't blown.

I suppose the next thing to try would be to get some door actuators at the salvage yard. I have another door I recently took at the salvage yard to replace mine but the door actuators seem a little involved to get to as they appear to be inside the door itself not just behind the panel. :?

It's just strange as I can hear a very faint click from the relay when I turn the key that tells me the Central Locking does seem to be working, as well as the gas door recieved the signal, it's just that the driver and passenger doors (and as such also the rear doors as I understand they run off the front door signals) are either no longer getting the signal or just not responding for some reason.

Nonetheless, thanks for the response! I'll keep digging.

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