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1970-1995 Range Rover Classic
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Discussion Starter #1
The factory-fitted system is designed to automatically adjust the side mirrors whenever the seat is adjusted. Over time, the switches move the mirrors but not the seats. The problem can be caused by faulty contacts in the switch unit, but also by damage to the electronic control unit under the seat. The latter has a battery hard-wired into the printed circuit board. When this battery leaks it usually damages the board and/or various component parts. While it is possible to fix any damage and replace the battery, the result is rarely reliable. For this reason, many service shops refuse to work on them. OEM replacement control units and switch packs are very expensive. “Refurbished” units frequently have a poor performance record so many workshops will not use them.

I finally got tired of repairing the original seat controls with lack of success. They would work for a while, then revert to "mirrors moving only"

If you are a “purist” then this article is not for you. You will either have to pay the money for replacement parts and hope the repair lasts OR build a DIY switch unit. If you are prepared to do without a few inessential functions this article describes how to restore the backwards/forwards action, the back rest angle and the tilt for under $50. It will NOT raise or lower the seat or the headrest. The mirror adjustment will still operate using dashboard control.

Components

All parts are available from any electronics store or on-line. If you are experienced with electrical hook-ups there are other ways to make the connections but the following are the simplest:

3 X “centre-off” 6-pin toggle switches. The functions must be “ON-OFF-ON” (Switches without the centre “off” will not work)
2 X small connector strips AND forked spade connectors
3 mm auto wire in at least two different colours
Cable ties and heat-shrink tubing.
A box in which to mount the switches -( you can make one but diecast alloy ones are cheap and convenient)
A few small Philips-head self-tapping screws

Switch wiring

First, make up the three new wiring looms. Do not try to economize on cable – it is cheap and if you cut it too short, it will make the job much harder.

power_supply_wiring_for switch.jpg switch_with_all_ wiring.jpg

Each switch requires a positive wire in plus a bridging wire screwed to ONE corner pole. The bridging wire then loops across to the OPPOSITE corner pole. Replicate this arrangement with the negative wires. Though not essential, using different wire colors for positive and negative makes it easier to keep track of the wiring

The centre terminals are the ones that connect to the motors. With the switch in one “on” position, one cable becomes positive, the other negative. When the switch is moved to the alternative “on position, the polarity is reversed, making the motor run in the opposite direction.

Make up all three switches in an identical way.It is also not essential to use different wiring colours but it makes it easier to keep track of what you are doing. It also helps to tape these wires in pairs. On this switch, light and dark green wires are paired and taped.

Assembling the mounting box

mounting_box_drilled.jpg

The box in the pictures is an excellent size to mount all three switches and hide most of the wiring. Mark all holes so there is clearance space between the switches, also room to get a screwdriver between them to mount the box to the seat frame. The mounting screws go through the small holes and the corresponding larger holes on the opposite side are big enough to get the screwdriver right through.

Install the switches into the box so that all the switch controls move the same way (forward or backwards etc). Tidy up the wiring with small cable ties. Do NOT mount the box onto the seat frame just yet- that would just make it harder to join the looms.

Preparing the power connection

The three pairs (3 black negative) and (3 red positive) wires now hanging out of the new switch pack need to be joined into the main seat wiring loom and this where the use of the connector strips will make life much easier. By a bit of simple bridging, the power connections to the loom will be reduced to ONE positive and ONE negative. You could use a "busbar" but the simple loops are just as efficient. Obviously negative and positive wires must be kept isolated.

A small section of heat-shrink over the "double" wires helps to keep them in place while being assembled. Note the small cable ties keep everything neat and help take the strain off the connections.

power_connections.jpg

Leave the new box at the front of the seat (along with the other sets of wires that will go to the motors), slide all of the power-supply wires under and towards the back of the seat where you can reach them. Tidy it all up with cable ties but leave the ECU un-mounted for the moment

The ECU has several looms attached to it with multi-plugs. You want the large bundle containing a fat white/red wire and some black wires. Cut 10 mm of shielding from each of these two wires and affix (preferably solder) your new red to the white/red wire and your black to the black wire in the loom. NOTE – both of these wires are switched so will not register any connectivity without ignition.

Wiring the switches to the motors

It is nearly impossible to access the solder contacts between the wiring loom and each motor. Reach through from behind the seat and unclip the multi-plug that has ONLY yellow and green wires. Pull this loom forward so you can work on it from the front.

WITH THE VEHICLE BATTERY DISCONNECTED, clip temporary positive and negative cables long enough to reach from the vehicle battery to the contacts of the motors under the seat.

Each motor draws power via one pair of yellow and green wires. The pins in the multi-plug make it easy to find the relevant wiring combinations. By touching your temporary positive lead to the pin of one yellow wire and your temporary negative lead to the pin of the opposite green wire you can easily work out which sets of wires control the various functions). Just reverse the leads to change direction of the motor. Do NOT let the leads touch each other.

The easiest way to make the permanent connections is to work one pair of yellow and green wires at a time, cut and strip the ends and join a pair of wires from your new switches using plastic connector strips. That way everything stays neat

Finally

Connect the starting battery, turn on the ignition and TEST the switch operations to ensure you have slide, tilt and rake adjustments in both directions. It is entirely possible that some or all of your original seat switch functions will work too, but that is a bonus.

Drill a couple of small holes and mount the box with self-tapping screws onto the seat frame in some convenient location. Tidy everything up using wire-ties, re-attach the seat loom to the multi-plug and remount the ECU under seat frame. ALL DONE!

new_controls_installed.jpg
 

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1970-1995 Range Rover Classic
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brilliant write up. One problem... if this is for a 95 RRC / memory seat model, and somebody else can chime in if they disagree, but the voltage sent to the motors is less than 12 volts, and regulated by the seat ECU. Therefore, if you are sending 12 volts to the motors without the ECU it may work here and there, but over time you will not have a long lasting solution...
 

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Discussion Starter #3
Thanks for the feedback. I'm the first to admit this fix was never based on science, but on practicality. The vehicle is a 93 SE and yes, it is /was a memory seat version.

You may well be right about the voltage input but that is one reason I took the feed from the cables between the ECU and the motors. Also, this is an operation that will get used very infrequently - once set there will be no need to change the seat settings unless a different driver uses the vehicle - In my case never. In practice, this means the new switches merely sit in "off" mode pretty well permanently.

Just for interest, I also have a 91 Range Rover High-line and swapped the original seats for P38 leather electric seats. I did not want the memory or mirror functions in that one either, so merely connected the existing motors and switch wiring to a power supply. It has functioned perfectly for several years.
 

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I totally agree with you.... if you were applying voltage to these motors constantly, i would bet you might fry them, but just once now and then / its the same thing as using a power probe (which i used to do before fixing my seat ecu) =)

still.... excellent write up...
 

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brilliant write up. One problem... if this is for a 95 RRC / memory seat model, and somebody else can chime in if they disagree, but the voltage sent to the motors is less than 12 volts, and regulated by the seat ECU. Therefore, if you are sending 12 volts to the motors without the ECU it may work here and there, but over time you will not have a long lasting solution...
On 95 RRC, front passenger seat is not controlled by seat ECU. Voltages come directly from battery via control switches.
 

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Reviving this thread for some questions. When I started fooling around with the seat problems, I thought of doing something along the lines of this project.

Evidently my ECU just started dying. The driver's seat won't stop moving rearward. Even when it reaches its end, the ECU continues to try to push it further back. I confirmed that it is the ECU by disconnecting the motors, and disconnecting the switch. When the door opens, or when the key is turned, there is a repeated clicking coming from a silver box under the seat. I managed to hot-wire the seat back into the proper position, then I pulled the fuse for the seat. Although I don't adjust the seat much, it's annoying to leave like that, and I think this also disables the mirrors, right? The seat movement works very well in all directions. The switch is clean, but the back adjust is not in good order. So....
  1. Is there any way to easily disable just the forward/back (bad part) of the ECU, while leaving the others to keep working?
  2. Is there any way to get to the ECU short of removing the seat?
  3. Is there any way to be able to adjust the mirrors if the seat is disabled?
 

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1970-1995 Range Rover Classic
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Reviving this thread for some questions. When I started fooling around with the seat problems, I thought of doing something along the lines of this project.

Evidently my ECU just started dying. The driver's seat won't stop moving rearward. Even when it reaches its end, the ECU continues to try to push it further back. I confirmed that it is the ECU by disconnecting the motors, and disconnecting the switch. When the door opens, or when the key is turned, there is a repeated clicking coming from a silver box under the seat. I managed to hot-wire the seat back into the proper position, then I pulled the fuse for the seat. Although I don't adjust the seat much, it's annoying to leave like that, and I think this also disables the mirrors, right? The seat movement works very well in all directions. The switch is clean, but the back adjust is not in good order. So....
  1. Is there any way to easily disable just the forward/back (bad part) of the ECU, while leaving the others to keep working?
  2. Is there any way to get to the ECU short of removing the seat?
  3. Is there any way to be able to adjust the mirrors if the seat is disabled?
if you have a LWB it’s a walk in the park, cut the zip ties and pull all the connectors out and you’re good to go. SWB might be a little tighter
 

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For #1 disabling inside the ECU may be difficult, but you could disconnect the wires for that motor by pulling the pins at the connector. They relay inside the ECU would always be triggered, but it doesn't seem like it would harm anything.

For #2 I agree with xalt. I have uninstalled and reinstalled them on my trucks without removing the seats. If the seat can still be moved then it is pretty easy. I would recommend raising the back of the cushion as high as it will go. Raising the front doesn't really help or hurt much. As far as forward/back it is actually easier when it is back rather than forward. Lay down on the floor in the back with a flashlight and you can get to everything. Start with the easy connections like the one for the motors on the back. The hardest is the big, double connector on the right and the small connector that is far forward on the left. I disconnect the one on the left last when uninstalling and first when re-installing.

A couple of them clip into the metal under the seat and you need to release the clips so you can manipulate the connector to unplug them. The only other potentially confusing part is the quarter-turn knob that attaches the left side of the ECU.

It is oriented like this when installed in the truck if you are looking at it from the back.
284197
 

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RIchard55 - I like your remote/external Varta battery. I may have to borrow that idea!
 

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I don't trust the new battery not to leak like the old ones over time so I decided keeping it away from the PCB by mounting it in a separate enclosure was the safest path. The seat ECUs are hard enough to source that I don't want to take chances with any working ones I can get.
 

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The hardest is the big, double connector on the right and the small connector that is far forward on the left. I disconnect the one on the left last when uninstalling and first when re-installing.
I un-plugged everything but that big connector on the right! I've got big hands which complicate the issue, and I left the seat in my standard driving position (so I don't have to hurry to relocate the battery).
 

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The three pairs (3 black negative) and (3 red positive) wires now hanging out of the new switch pack need to be joined into the main seat wiring loom and this where the use of the connector strips will make life much easier. By a bit of simple bridging, the power connections to the loom will be reduced to ONE positive and ONE negative. You could use a "busbar" but the simple loops are just as efficient. Obviously negative and positive wires must be kept isolated.
I printed Aussiebushman's writeup for future reference, but the section above has me confused as he seemed to just gloss over the use of, and connections to, these "connector strips".

What exactly are they? HOW do the switch wires connect to it? I get that we're combining 3 pos and 3 neg wires from the switches going IN to the connector(s) and 1 pos and 1 neg coming OUT (I think...), but a little more clarity about how to utilize these connector strips would help me (and others) a lot.
 

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Couldn't you salvage a passenger seat harness to use on the drivers side, effectively making a power-non-memory seat? You may have to swap pins, and work out the mirrors, but seems a simple solution if you don't want to make your own harness.
 

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1995 Range Rover County LWB
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I just pulled the ECU out of my 95 RR LWB. Does anyone have a current source for refurbishing them? Like everyone else, the battery has leaked and left quite a bit of corrosion on the circuit board. I definitely love Richard55's external battery mod, btw.
 

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For #1 disabling inside the ECU may be difficult, but you could disconnect the wires for that motor by pulling the pins at the connector. They relay inside the ECU would always be triggered, but it doesn't seem like it would harm anything.

For #2 I agree with xalt. I have uninstalled and reinstalled them on my trucks without removing the seats. If the seat can still be moved then it is pretty easy. I would recommend raising the back of the cushion as high as it will go. Raising the front doesn't really help or hurt much. As far as forward/back it is actually easier when it is back rather than forward. Lay down on the floor in the back with a flashlight and you can get to everything. Start with the easy connections like the one for the motors on the back. The hardest is the big, double connector on the right and the small connector that is far forward on the left. I disconnect the one on the left last when uninstalling and first when re-installing.

A couple of them clip into the metal under the seat and you need to release the clips so you can manipulate the connector to unplug them. The only other potentially confusing part is the quarter-turn knob that attaches the left side of the ECU.

It is oriented like this when installed in the truck if you are looking at it from the back.
View attachment 284197
Richard55 - may I ask which Varta battery you used for the replacement?
 

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1970-1995 Range Rover Classic
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2000IQ move - don’t bother with a battery at all unless you actually need memory functions. that’s what i did

proper parts are the only guys who refurbish (throw away old board and reuse case/connectors) at $470 a piece. no memory functionality but does have working mirrors. would try cleaning it at the very least before you shell out that money.
 

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2000IQ move - don’t bother with a battery at all unless you actually need memory functions. that’s what i did.
Do all seat/mirror functions work with the battery removed?
 

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I did not know that. Now I think I’ll make my external battery pluggable!
 
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