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Door lock problems

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
1997 - 2000 V70-XC
1997 - 2004 C70

phidoe2000
Posts: 19
Joined: Wed Jun 27, 2012 5:22 am
Year and Model: 98 V70XC
Location: FL, USA

Door lock problems

Post by phidoe2000 »

Hi Everyone, I'm hoping to get some help. I have a 98 V70 XC. The rear doors will lock, but not unlock using the central lock button nor the key in the drivers door lock. I do not have a key fob. I've replaced both actuators with used units. How do I chase this issue down if it's a wiring, relay, or fuse issue? Is there anything in particular that is unique on these cars to the rear doors? Thanks in advance for any help. Ken
jimmy57
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Re: Door lock problems

Post by jimmy57 »

How adventuresome are you?

Your used units probably have the same issue with the protection resistor failing that the originals had. When I did pick n pull used ones I had the same problem as the originals on mine.

The motor that is built into the latch/lock assembly has a PTC resistor that acts to protect motor from burn out from playing with lock buttons or a stuck system relay. I have never heard of a failure like that of the Denso (Toyota) supplied VGLA locking control that your car has. The resistor is in the end cap of the little DC motor for locking/unlocking. The resistor can be removed and all works great. I did it on mine more than a year ago and no more problems. I bet you will see that your lock knobs move a faint amount up before they quit. Unlocking requires more effort and the extra resistance of the failed PTC is not giving the current needed to unlock before it shuts off current.

If you pry carefully around the lock case and snap out the motor and then pry the two dimpled areas holding on the end cover of motor, you can get the PTC out and replace it with a strip of copper or aluminum and then re-assemble the motor. The lock can be glued and screwed together. I used silicone sealer around perimeter and used one sheet metal screw run through the case where I could see it cleared all linkage and internal parts.
The PTC is stuck into a slot where you see it is the bridge between the incoming terminal and the arm the brush is on.
It is 7mm by 10mm and about 1 mm thick. Looks to be aluminum with a black center. I had some 10 gauge copper single strand wire and I hammered a short piece flat and inserted it. Some other metal could be used if you have anything else you could put your hands on the make a jumper out of.
OR, you go buy two new lock assemblies.
My driver's side had to be replaced due to a broken piece and my passenger front is beginning to show signs of it being sluggish so I will be repairing one day soon.

This issue afflicts other Volvos too. I have done PTC bypass or cleaning on the RWD models. Those units have the PTC outside of motor inside the lock motor unit.
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rspi
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Re: Door lock problems

Post by rspi »

Man, I am really tired of fooling with the locks on our car. Is there a picture of that part somewhere so I can go yank mine out? I thougth the motor was weak and no longer able to push the pin up. :?
'95 855 T-5R M, Panther - 22/28 mpg
'98 S70 GLT, Lil' Red 25/32 mpg
--------------------
Volvo's of past: '87 740 GLE, '79 262C Bertone, '78 264, 960's, '98 S70 GLT, '95 850 T-5R YellowVolvo Repair Videos
phidoe2000
Posts: 19
Joined: Wed Jun 27, 2012 5:22 am
Year and Model: 98 V70XC
Location: FL, USA

Re: Door lock problems

Post by phidoe2000 »

Thanks Jimmy.....I'm extremely adventurous...heard that taking these actuators apart can do a number on your hands as well. I now have an extra unit, so I will be attempting the repair you mentioned. I'll let you know how it goes. I have another used unit ordered and in the way. I even took a right side actuator and hooked it up on the left (left it dangling) to see if I got any movement in the lock mechanism and didn't, so this is worth a try. The most recent actuator was listed that is was checked and is fully functional, so hopefully I can repair one, and just replace the other. Ken
Last edited by phidoe2000 on Wed Jun 27, 2012 1:44 pm, edited 1 time in total.
jimmy57
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Re: Door lock problems

Post by jimmy57 »

rspi wrote:Man, I am really tired of fooling with the locks on our car. Is there a picture of that part somewhere so I can go yank mine out? I thougth the motor was weak and no longer able to push the pin up. :?
The 93-97 800's have a different lock/latch assembly and I have never taken one apart but the PTC is in those too. I think the lock motor is separate motor but is attached to the latch assembly. It should be one where there is a slightly smaller than a dime silver disc inside the case but not inside the motor itself once the unit is opened.
phidoe2000
Posts: 19
Joined: Wed Jun 27, 2012 5:22 am
Year and Model: 98 V70XC
Location: FL, USA

Re: Door lock problems

Post by phidoe2000 »

Ok.....problem solved!! Thank you Jimmy! Let me tell you what did to fix one of my locks. I removed the back of the motor housing. It's the largest flat area on the actuator.....just pry the cover off gently. Inside you'll see the motor and two large white gears. The motor will pop out easily. Remove the aluminum cover from the motor....this was the hardest part for me. I used a very small flat headed screw driver to gently pry the two tabs up until I could get my needle nose pliers on the tabs and straighten them out enough to slide the motor cover off. Now look into the inside of the plastic cap and you'll see the two leads that protrude outside the cap. You'll notice a nice maze of copper that runs the perimeter of the cap. On one side you'll see a square peice about a cm square. This peice is inserted between two pieces of copper.....book stacked if you please. Grab that pieces with your needle nose and pull it out. Replace it with section of conductive material. I used a link of copper chain and it fit perfect. Put everything back together and hook it up and test.

I did this and the lock began to move again, however, it still wasn't functioning fully. My Volvo mechanic had recommended that I tear open the actuator and remove a heavy spring that was inside directly linked into the lock mechanism. I noticed the spring but it wasn't on the inside, rather, it resides next to the obvious red button-like dot you can see very clearly. I popped it off and presto, the lock worked perfectly again!

Sorry this is long but I searched for two weeks for advice other than "replace the actuators" and wanted to share. Took me an hour. Thanks.....Ken
ct98saffv70r
Posts: 16
Joined: Mon Jun 25, 2012 11:23 pm
Year and Model: 98 v70r
Location: Norwich, ct

Re: Door lock problems

Post by ct98saffv70r »

now, if we only had pics!! i think this is the same issue on my 98 v70r. they go down just fine on the front passenger and rear driver door, but don't go up. i think they budge a little, but don't pop up tp unlock. The dealer who sold me the car told me that it probably just needed some silicone lubricant to work again. i kinda figured it was BS.

Is there a definitive tutorial with pics on how to perform this? i'd like to tackle this soon! if not, i guess i'll try to take a whole bunch of pics of the process.
phidoe2000
Posts: 19
Joined: Wed Jun 27, 2012 5:22 am
Year and Model: 98 V70XC
Location: FL, USA

Re: Door lock problems

Post by phidoe2000 »

If I were you, I'd pop the door panel off. There's a plastic moulded cover over the access hole for the actuator. Pull that off. You can see and access the spring from there with a needle nose. Pop the spring off and try the lock. I believe this will work for you since you have some movement still there. You don't have to remove anything else if it works. Sorry about the lack of pictures. I wasn't sure where I was going until I got there if you know what I mean. I might go ahead and take apart my extra actuator just so I can post it here. Ken
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rspi
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Re: Door lock problems

Post by rspi »

jimmy57 wrote:The 93-97 800's have a different lock/latch assembly and I have never taken one apart but the PTC is in those too. I think the lock motor is separate motor but is attached to the latch assembly. It should be one where there is a slightly smaller than a dime silver disc inside the case but not inside the motor itself once the unit is opened.
No, we also have a S70 that has these door latch problems. Are you saying that the part i need to replace is INSIDE the motor?
'95 855 T-5R M, Panther - 22/28 mpg
'98 S70 GLT, Lil' Red 25/32 mpg
--------------------
Volvo's of past: '87 740 GLE, '79 262C Bertone, '78 264, 960's, '98 S70 GLT, '95 850 T-5R YellowVolvo Repair Videos
jimmy57
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Re: Door lock problems

Post by jimmy57 »

Yes. The earlier system has the PTC resistor wafer outside the physical motor case but inside the lock actuator plastic housing.
98 brought the change of putting the wafer in the inside of the motor end case that carries the brushes.

The spring part is puzzling to me. My locks worked fine, not too forceful on lock or unlock, but not at all sluggish either and they complete either function completely with that spring still in place.
My first effort was to lube the motor inside and to eliminate the spring. The spring removal there increased function and made the door I worked on have unlocking more of the time until the temp went over 80 degrees or so inside the car.
I got another used latch assy, plugged it in, and it wouldn't unlock completely. I took it apart knowing the pattern of the PTC failure and determined to find where they hid the PTC. The PTC has 2 ohms or so of resistance before heating so I did continuity testing between connector and the two pins that stick up for the motor to insert over for the motor connection (this is inside the black latch cover where a motor "bump" can be seen). I found there was no resistance so the PTC wasn't imbedded in the plastic where the leads are connected and the conductors disappear as they cross the latch assy. This left the motor itself as being the only place the PTC can be hidden. I took apart the motor on the first latch i had sort of butchered and found the PTC.
I tested that motor by inserting wires into the two connector ports and found the motor was weak and barely spun. I pried the tabs open and got the end cap off and found the PTC and substituted a copper jumper for the PTC wafer and then put the motor end case back on. The motor then had torque and spun fast. BINGO!
Then I took apart my newly picked n pulled $5 latch and did the PTC bypass surgery. Lock worked fine. I did the same fix on the other rear door. My left front lock module got replaced with new as it had a broken arm where lock knob rod attaches and the RF is working fine today but could go under the prying screwdriver for surgery if it ever takes ill.
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