Volvo Community Forum. The Forums of the Volvo Owners Club

Forum Rules Volvo Owners Club About VOC Volvo Gallery Links Volvo History Volvo Press
Go Back   Volvo Owners Club Forum > "Technical Topics" > 850 / S70 & V70 '96-'99 / C70 '97-'05 General > 850/x70 S1 Articles
Register Members CarsBlogs Help Calendar Mark Forums Read

Notices

850/x70 S1 Articles How to's and step by step guides on a specific repair or modification to a Volvo 850/70 car.

Information
  • VOC Members: There is no login facility using your VOC membership number or the details from page 3 of the club magazine. You need to register in the normal way
  • AOL Customers: Make sure you check the 'Remember me' check box otherwise the AOL system may log you out during the session. This is a known issue with AOL.
  • AOL, Yahoo and Plus.net users. Forum owners such as us are finding that AOL, Yahoo and Plus.net are blocking a lot of email generated from forums. This may mean your registration activation and other emails will not get to you, or they may appear in your spam mailbox

Thread Informations

Electric seat diagnosis

Views : 766

Replies : 10

Users Viewing This Thread :  

 
 
Thread Tools Display Modes
Old Jun 15th, 2018, 23:15   #1
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default Electric seat diagnosis

The electric seat on the V70 and similar with the memory function is fairly easy to diagnose when it fails. The faults that are likely to occur fall into two broad catagories;
1) Faults with the motor/s and associated harnesses
2) Faults with the switch panel and associated harness

There is, of course, the possibilty that a fault could have occurred in the control module under the seat, however this is much more unlikely than a straightforward electro-mechanical fault elsewhere on the seat, so unless all other avenues have been explored, it's not worth swapping-out the module. Likewise, if the power to the seat has failed at the fusebox, etc., then that will need dealing-with first.

To narrow the two categories down, a few tests of the switch panel are required;

a) Does the seat move with any switch input at all? If not, then check the fusebox and the supply +12v and ground to the seat module first, before stripping the switch panel out for further tests

b) Does the seat not move on one or more switch inputs, but otherwise moves if the Memory buttons 1, 2, 3 are pressed? Again, the seat switch panel needs stripping out and repairing.

c) Does the seat not move on some switch inputs, but a clicking can be heard from under the seat on those failed movements? This is more likely to be the motor/s within the seat, requiring the seat itself to be stripped down. If the backrest angle function is the failed movement, this can be done with the seat in-situ in the car, otherwise it is going to be easier to remove the seat completely in order to repair it, as the raise/lower and forwards/backwards motors are all underneath the seat cushion - very tight to access for motor removal.
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 16th, 2018, 00:52   #2
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default Electric seat switch-panel removal

Assuming that the seat is making no clicking noises, the switch panel is the likely area of failure in the V70 electric seat. It is fairly exposed to the weather when the door is open, but also incorporates some fragile (in old age) circuit-board electrics. As I will explain later in this thread, there is one specific area that is likely to fail in old age, which is very easy to repair with a soldering iron (small tip circa 1mm required), some solder, and a little time. You will also need a 12v test-lamp with its own built-in battery for continuity testing (a 12v battery, some wire, and a 12v/5W sidelamp bulb will make a good tester), or a simple electrical meter with a Resistance function will suffice.

The first job is to safely remove the switch panel from the side of the seat. There is no need to disconnect the main vehicle battery for this work, though caution is needed to ensure that all correct procedures around the airbag system are adhered-to. It will help with diagnosis and confirmation-of-repair if the seat module is otherwise left powered-up, which is its normal state with the ignition key in the "OFF" position, or even out of the column.

The main thing is to make the seat panel as easy to maneouvre as possible, so that means disconnection of the green multiway plug on the front of the seat module that feeds the harness going across to the switch panel. Volvo have chosen to make thsi plug as fiddly to remove as possible; the latch that needs to be depressed into the plug to release it from the module is facing down towards the module mounting panel. A small digit can just squeeze into the gap to push the latch whilst the plug is gentle wiggled free.

Release any tie-wraps securing the harness to the seat frame.

(see photo 1) Lift the front-facing edge of the switch panel straight upwards to release it from the airbag trigger housing, then knock it backwards towards the rear seat to disengage it from the seat tubular piece near the seat buckle. IT IS IMPERATIVE THAT THE SEAT SIDE AIRBAG TRIGGER IS NOT ACCIDENTALLY PUSHED TOWARDS THE SEAT CUSHION DURING THIS STAGE.

As soon as the switch panel and seat trim surround is loose from the seat, carefully remove the inhibitor (orange coloured) plastic piece from its stowage under the trim panel, and insert it between the inner and outer parts of the side airbag trigger unit. Do not knock or accidentally push the trigger face towards the seat. Once the inhibitor piece is in place, things are much safer to work-on.

The switch panel can be removed from the seat side trim panel on the workbench. There are three screws (Torx T20) securing the switch panel. The tie-wrap securing the harness to the seat trim near the airbag trigger clipping area will need to be cut to release the harness. It is important on reassembly to renew this tie-wrap, as it prevents the seat switch harness from fouling the airbag trigger unit.

(see photo2) Release the plastic latch at one end of the switch panel, and push the panel upwards (in its normal, fitted orientation in the car) out of the trim. It might be a bit tight on its dovetailing, but it will just slide out. Guide the harness through the trim, and then the module connector plug.

The switch panel can be further dismantled by removing 8x screws securing the circuit board to the switch front panel. Note that two (ringed) are also cord-grip screws. It is important that the switch buttons are facing down towards the workbench, and stay in that orientation during this work. There are four tiny springs (yellow-ringed in photo3) that will escape from the memory buttons if the panel is inverted, then there will be fun trying to find then, let alone feed them back into the buttons. Just work with the circuit board facing upwards towards you.

(see photo3) The main concern on this circuit board is the harness connection plug that is header'd onto the circuitry (red-ringed in photo); the joint is mechanically loaded, and the solder cracks. It is obvious from each of the microswitch units where the circuits go, and the best test is to operate the switches in turn and measure the continuity to the common 12v feed to them. This is the main circuit around the outside of the circuitboard, it is fed by the Orange and Blue wires in parallel to each other (either will work as a test-point). If the header solder joints have both failed on these two wires, then all switch functions will cease to work, hence this switch panel is a valid part of the overall seat diagnostics after a fusebox check for supply voltage. The wire colour that feeds the main seat module (pin_1 on plug A) is a Green with a Red tracer, and this should have 12v on it permanently when the car is "awake" with the doors open.

All the microswitches have a unique wire colour which should show good continuity to the Orange or Blue wires as each is pressed. Note that the switch contacts are made on each unit in the opposite direction to that which the switch is pushed. The functions and their wire colours are;

Forwards - Red wire
Backwards - Black wire
Rear raise - Yellow/white wire
Rear lower - Orange/white wire
Front raise - Brown/white wire
Front lower - Red/white wire
Backrest raise - Violet wire
Backrest lower - Green/white wire

(see photo4) It is likely that a close inspection of the header joint for the harness plug has broken (cracked or "dirty" looking solder) joints on one or more pins (see close-up photo). To rectify this, the joint should be heated with a fine-tip iron, wiped clean of old solder (an old cloth will suffice), the joint fluxed slightly, and new solder added back into the joint. The important thing is to work progressively through all the affected joints in turn, and avoid bridging across between the pins with solder that is being removed/added.

Reassembly, as they say, is the reverse of disassembly, but it is well worth doing a series of checks before putting everything back. Firstly, check for continuity between all adjacent pins - there should be none, except the diagnostic resistance pins with the Yellow and the Grey wires - that is normal. Secondly, assemble the switch button panel back to the circuit board, then plug it into the car and check that everything is now working - don't panic if it doesn't, as if the switches have been duff for a while, there is a chance the motor/s have seized in the meantime from lack of use. That is a further repair!

Remember to secure the harness lead inside the seat side trim over the airbag trigger moldings (that clip the trim down over the airbag trigger) with a new tie-wrap, and leave the harness plug loose whilst the switches/trim are refitted to the seat - it will lessen the chance of the airbag trigger being pushed accidentally once the orange piece has been removed and re-stowed. Locate the trim panel first over the tube at the rear edge of the seat, ensuring the seat buckle is clear of the area, then lower the front of the trim panel squarely over the side airbag trigger housing, and push downwards to latch.

If the seat motors need investigation, that is to be continued....

Apologies for lack of photos - forum is having difficulty uploading these right now. To be added later.
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 16th, 2018, 10:49   #3
Baffler
Premier Member
 
Baffler's Avatar
 

Last Online: Jun 15th, 2019 08:59
Join Date: Dec 2002
Location: Co. Limerick, Ireland
Default

Brilliant, SwedishBus, great write up so far! Many thanks in advance for going to such lengths!

If you're having difficulty uploading pics it could be that they're too big...? Do you have a means to resize them such as Microsoft Office Picture Manager or Image Resizer for Windows?
__________________
Liam...
'96 854 TDI SE (D5252T/M56)
'99 V70 2.5D S (D5252T/M56)
'98 V70 2.5T SE LHD (B5254T/AW50-42)
'05 C70 2.0T Collection (B5204T4/AW55-50)
Baffler is offline  
Old Jun 16th, 2018, 23:37   #4
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default

Quote:
Originally Posted by Baffler View Post
Brilliant, SwedishBus, great write up so far! Many thanks in advance for going to such lengths!

If you're having difficulty uploading pics it could be that they're too big...? Do you have a means to resize them such as Microsoft Office Picture Manager or Image Resizer for Windows?
Hi Baffler,
Yes, I had already resized them down again - I normally resize photos for other forums to 450kB max, but I see this forum needs them much smaller. There are four shots that are around 250kB apiece, but I will double-check that the pixel count also meets the forum requirements.

To be frank, I'm probably struggling because of my geographic location; we are the land that time forgot as far as broadband is concerned - as well as any governments!

I'll keep trying, as a picture speaks a thousand words, and I'll do the write-up on the seat motor repair ASAP. If you are having trouble with your base motors, that is the fore/aft slides, and the cushion raise/lower functions, then the seat/s will need to come out, as I think motor access is just too tight against the floorpan.
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 16th, 2018, 23:46   #5
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default

Photo_1 Switch panel removal;
D5252T_seat_switches_removal.jpg

Photo_2 Switches being dismantled;
D5252T_seat_switches_dismantle1.jpg

Photo_3 Switches exposed for working-on;
D5252T_seat_switches_dismantle2.jpg

Photo_4 Detail on dry-joint inspection;
D5252T_seat_switches_dryjoint.jpg
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 18th, 2018, 09:40   #6
Baffler
Premier Member
 
Baffler's Avatar
 

Last Online: Jun 15th, 2019 08:59
Join Date: Dec 2002
Location: Co. Limerick, Ireland
Default

Quote:
Originally Posted by SwedishBus View Post
Hi Baffler,
Yes, I had already resized them down again - I normally resize photos for other forums to 450kB max, but I see this forum needs them much smaller. There are four shots that are around 250kB apiece, but I will double-check that the pixel count also meets the forum requirements.

To be frank, I'm probably struggling because of my geographic location; we are the land that time forgot as far as broadband is concerned - as well as any governments!

I'll keep trying, as a picture speaks a thousand words, and I'll do the write-up on the seat motor repair ASAP.
That would be great! Thanks so much, SB! Pictures are indeed invaluable

I see you and others have managed to attach them directly to the page as opposed to a thumbnail...what option does one need to select in order to make them appear like so?


Quote:
Originally Posted by SwedishBus View Post
If you are having trouble with your base motors, that is the fore/aft slides, and the cushion raise/lower functions, then the seat/s will need to come out, as I think motor access is just too tight against the floorpan.
If I remember correctly it was only the drivers fore/aft and passenger backrest that nothing was happening...all other functions were there so I'm hoping it's just a bad solder joint in both cases. I had managed to remove both front seats for inspection, removed and stripped the drivers control panel and gave it several blasts with contact cleaner but never thought to inspect and solder the joints

I'll get another look later in the summer as we only just bought the car early last July so my priority was to get it 100% mechanically for its trip across Europe. Never missed a beat, by the way, but do you know what makes this thread even more interesting...it was originally registered in Sweden making it a proper Swedish Bus
Attached Images
File Type: jpg LHD V70 3.jpg (306.3 KB, 0 views)
File Type: jpg LHD V70 2.jpg (375.9 KB, 1 views)
__________________
Liam...
'96 854 TDI SE (D5252T/M56)
'99 V70 2.5D S (D5252T/M56)
'98 V70 2.5T SE LHD (B5254T/AW50-42)
'05 C70 2.0T Collection (B5204T4/AW55-50)
Baffler is offline  
Old Jun 18th, 2018, 22:53   #7
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default

It sounds like you need my next stage of the post!

I am sure, from your description, that your problem is a dirty commutator and/or brush-box on the seat recline motor.

This is the one motor you can do with the seat in-situ, and is not a bad job to do at-all. The motor will have to come out onto the bench, but once you have it loose, I reckon you could fix this in 40minutes.

I'll try and get the next bit uploaded ASAP, but in the meantime, double check whether you are getting a distinct "click" when you try to operate the seat recline button in either direction. If you are, job is in the motor or its wiring from under the seat. If not, then the job is likely to be in the circuit board and wiring header as I described above. Good luck!

PS. Your car looks great in the thumbnails, and your seats are certainly in far better condition than mine. I have only had my second V70 (TDI) for 4weeks as a "wrecker", but it has potential - if it behaves itself after its engine rebuild!
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 19th, 2018, 13:53   #8
Baffler
Premier Member
 
Baffler's Avatar
 

Last Online: Jun 15th, 2019 08:59
Join Date: Dec 2002
Location: Co. Limerick, Ireland
Default

Quote:
Originally Posted by SwedishBus View Post
I am sure, from your description, that your problem is a dirty commutator and/or brush-box on the seat recline motor.

This is the one motor you can do with the seat in-situ, and is not a bad job to do at-all. The motor will have to come out onto the bench, but once you have it loose, I reckon you could fix this in 40minutes.

I'll try and get the next bit uploaded ASAP, but in the meantime, double check whether you are getting a distinct "click" when you try to operate the seat recline button in either direction. If you are, job is in the motor or its wiring from under the seat. If not, then the job is likely to be in the circuit board and wiring header as I described above. Good luck!
Duly noted! Will check what's going on next time we're in Poland. I look forward to your next installment

Quote:
Originally Posted by SwedishBus View Post
PS. Your car looks great in the thumbnails, and your seats are certainly in far better condition than mine. I have only had my second V70 (TDI) for 4weeks as a "wrecker", but it has potential - if it behaves itself after its engine rebuild!
Thanks SB! The seats are indeed like new and for a 2.5T it's only run-in at 190k kilometers (118k miles). After driving it from Ireland to Poland I knew I wanted another, for daily use, so when we returned to Ireland I sold our '03 S40 and bought the 2.5D V70 last September. Am I mad? Yes!
__________________
Liam...
'96 854 TDI SE (D5252T/M56)
'99 V70 2.5D S (D5252T/M56)
'98 V70 2.5T SE LHD (B5254T/AW50-42)
'05 C70 2.0T Collection (B5204T4/AW55-50)
Baffler is offline  
Old Jun 25th, 2018, 21:45   #9
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default Failed seat recliner motor

Assuming that the seat recliner motor is being fed a supply voltage, but is not responding, the most likely scenario is that the commutator segments at the present (stopped) position are contaminated. This happens if the motor is stopped in one position without being used for several months.

To access the motor, the procedure is very much like that to access the "transmission" on the 850 for the seat-recliner that richard describes on his YouTube channel. The difference is that the motor drives the recliner mechanisms directly on the V70. Note that my pictures are taken on reassembly, so the hog-rings that are removed are depicted as plastic tie-wraps; these are a far better way of reassembling the seat. 4.8mm ties, roughly 150mm long are the easiest to work-with (they can be shorter, but it helps to have lots of spare length to aid reattachment of the covers).

The first thing to do is to remove the switch panel and protect the side airbag trigger as described above. It is worth leaving the switch panel plugged back in and resting in the front footwell, as it is necessary to move the seat forwards (if it will move) and raise the rear of the cushion upwards as far as it will go, in order to allow the recliner drive-bar to be extracted through the drivers door aperture.

The next thing is to remove the lumbar support knob and its trim from the seatback. This involves rotating the knob out as far as it will turn, pulling outwards sharply, and then turning further until it will extract from the seat.

The cover for the seat cushion will also need unclipping, as well as the trim for the lower part of the seatback (as richard describes). This is to access the wiring harness for the seat recliner motor, which passes over the front of the tubular cross-beam at the rear of the seat cushion. There are three hog-rings that need to be unclipped (screwdriver turning technique is the best) and the harness itself needs unsecuring from tubular cross-beam;

D5252T_seat_cushion_wiring_clipping.jpg

The cover for the lower part of the seatback has four hog-rings that secure the cover rods for the front/back of the cover together under its base - between the seatback and the cushion.

Unfurl the backrest cover over the plastic pieces that protect the sides of the backrest frame - use two hands to grip the cover down, then roll it over the plastic webs.

Go carefully when unclipping six more hog-rings that secure the front of the backrest cover to the foam at the front of the seatback - the foam will tear-out and leave the cover saggy if you are impatient. Once the cover is unclipped for the height of three sets of hog-rings, there is enough access for the seat recliner motor to be seen;

D5252T_seat_back_components.jpg

The motor is accessed by removing the spring that is circled above, then pulling the plastic seatback trim outwards towards the door aperture (one plastic stub to pull through the metal frame and retain), then a single screw is accessed through the drivers door aperture. The back side of the screw is visible on the picture below, which shows the general arrangement of the motor;

D5252T_seat_back_motor_fitted.jpg

Note that the motor has already been partially-stripped in this picture, as I will explain in the next post.
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
Old Jun 25th, 2018, 22:33   #10
SwedishBus
Member
 

Last Online: Today 14:23
Join Date: Oct 2014
Location: Isle of Skye
Default Seat motor strip

The motor components are showed laid-out on the picture below. The circled cover and insulator disc are pushed over the back of the motor itself, and are there to prevent anything shorting the two main supply pins in service. The pins are fed with 12v, either one polarity or another, depending on desired drive direction. The other 3pins are irrelevant for this exercise; they are there to sense the drive worm itself;

D5252T_seat_back_motor_components.jpg

To remove the motor, first unclip the spring from the seatback hole (both arrowed below) and allow the friction cord to hang loose from the recliner mechanism. This allows the mechanism to be turned easier for reassembly of the square drive-bar, as each side of the seat has an independent mechanism that needs fine adjustment to slide the bar in smoothly. Then remove the nut from the other end of the bar as circled (i.e. the tunnel side of the bar) then pull the square drive-bar out through the drivers door aperture and recover the nylon protective sleeve;

D5252T_seat_back_recliner_mech.jpg

Remove the motor to the bench, and strip off the bracket (two fixings circled yellow below) and remove the star-washer (circled orange below) to release the harness;

D5252T_seat_back_motor_dismantle1.jpg

Desolder the two main supply pins on the back of the motor. This is not strictly necessary, but it helps a lot with the reassembly of the motor end cover and brush-box. Then fold the two retaining tabs out (as arrowed) to release the motor end-cover. There is no internal spring pressure, so nothing will fly apart. The easier way of many to fold the tabs out is to use a small'ish pair of locking pliers with good square jaws. Lock them solidly over the square tab, and use the pliers to fold out the tab;

D5252T_seat_back_motor_dismantle2.jpg

The end-cover is keyed so that it will only assemble one way, but it can help to make a small Tipex or paint mark to help align the cover to the motor body. Just ease the cover back off the motor, and most likely the brush-box will come with it - no problem. This will then expose the commutator, which can be cleaned with a light abrasive (P1000 wet and dry paper) gently on the segments that are blackened. Switch-cleaner solvent or isopropenol alcohol is best for cleaning this up afterwards.

Check the brush-box for sticking brushes, but be careful not to displace the brushes out of the box. If they come out, you will need to feed the brush coil spring back in behind each one again, but they will tend to stay within the brush-box if they are not poked. Clean any excess solder from the brush-box contacts, then assemble the brush-box back over the commutator, using a fine screwdriver to ease the brushes outwards as they need to pass over the end of the segments.

Place the motor end cover over the brush-box, then test the motor with 12v in either direction to confirm it now works. If all is OK, resolder the harness back on again, otherwise give the commutator another clean to be sure. The tabs can be bent back over the motor end cover using the same technique with locking pliers.
__________________
1998 V70 2.5 10v petrol
1997 V70 2.5 TDI
SwedishBus is offline  
 

Tags
seat buttons?, seat electrics?, seat motors?


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 14:43.


Powered by vBulletin
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.