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Can anyone help me diagnose my speedo troubles on my '91 740 Turbo Wagon?
Neither the speedo nor either odometer is working any longer.
About half the time, the speedometer stays at zero, the other
half, the speedometer registers at about 30 mph, even if it's only that
the ignition switch has been put in the 'on' position without even
starting the engine. The odometers never move at this point, however.
It appears the wires are still connected at the rear axle, so do I have
a grounding problem in the dash? Do I need a new speedo head? Can I use
a speedometer from a 1994 940 instrument cluster that I already have?
Thanks for any advice!!!
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I know this is not the correct place for contact, but I tried emailing and from searching I see that email function on BB has been intermittently not working. I am interested in the '91 745ti you have for sale. If you would, please respond to this with alternate contact information. Thanks much.
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I'm amazed my little question sparked such discussion!
And such knowledge.
It also revealed that it was a repair beyond my own interest
in doing. SO,
I just sold the car on Craigslist, and away went my
troubles with it's ABS, interior, speedo, tires, battery,
and mouse infestation odor.
Don't worry, I still have my '94 945!
I've got a spare instrument cluster for that! :)
(now if only I could figure out where the loose connection
in the wiring for the gas-gauge is on that one -- someplace near
the dash -- If I bang on the cluster enough I get an accurate
reading 'til the next time I go over a bump!!!
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I just fixed mine 2nite!
Did all the capacitors, I mean all. Plus you need to retrace the circuit board paths due to the acid from the leaking capacitors.
This was hard because it was really hard to remap the board without knowing the original path. Turned out I needed to bridge a wire from one IC leg to a capacitor point.
The only way I knew the way was by comparing it to a good board.
Also, the tach needed a new 6.8 micro F capacitor. Fixed it!
One thing I learned is a good DMM meter can check the capacitor reading. GO THRU EACH ONE AND TEST THEM! A LEAK IS NOT THE ONLY SIGN.
Highly recommend taking the speedo apart by turning the dial counter clockwise and popping it of. Reset it with the needle at the k in km/hr at full clockwise spin. Take the odometer motor off and zip tying it to the board so it doesn't flop around. Just unsolder the 2 service light switch wires.
Very easy.
Now my speedo and tach work!
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Did you reset the needle by turning *clockwise* or *counter-clockwise* to the 'k' in km/hr?
Thanks for the great tips... just got mine fixed and almost back together.:-)
Thanks!
-Ryan
--
Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sway Bars, GT Braces, Dracos
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars
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sorry, been out of it for a couple of days
yes, you reset the needle going clockwise so it stops at the K
glad you got yours going
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What did you use to retrace the circuits?
I'm doing this probably Saturday. All new capacitors on the kitchen counter. :)
Thanks!
-Ryan
--
Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sway Bars, GT Braces, Dracos
1990 744GLE 189K 16-valve project
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars
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Well, took out my 92 740 speedo and compared it to the 91 speedo circuits.
The board has paths on both sides, so hold it up to the light and you can see better.
I leakings capacitors ruin the paths on the front side of the board.
I needed to take a little jumper wire from the 7th pin on one of the IC boards and over to the leg of the replaced capacitor.
I needed to check all continuity paths on boths sides of the board.
Remove the dial needle by lifting it up and over the stop pin and turn and pull CCwise. When you put it back on, set it so it full stops Cwise at over the k in km/hr bottom mark.
When taking apart the board, just desolder the service light wires off the board. I don't think you need to put this back, but check is it is an opne or closed condition that turns the service light on, and then mimmick it.
Undue the 2 little screws on the odometer motor with the worm gear. Take a small zip tie and tie the worm gear to the area over the rippon on the board. This way it doesn't flop around.
Then remove just two of the remaining 4 screws next to the center. I don't remember which two they are, but alone two are effective.
You will need a good desk lamp and tiny solder gun.
good luck
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Need more explanation on:
"tie the worm gear to the area over the rippon on the board."
"check is it is an opne or closed condition that turns the service light on, and then mimmick it."
What wattage soldering iron did you use?
--
See the 700/900 FAQ at the drop-down menu above right.
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sorry
when you unscrew the motor off the housing, tie it off to keep it from flopping around on the ribbon and maybe break the connection.
You will need to look at the board on both sides. And the motor tied off helps.
I just got a little zip tie and snugged it over the worm drive down onto the narrow projection of the circuit board.
The service light switch has to be unsoldered to separate the dial from board. I don't care about the service light ever working, so when the switch is in the down postion (light off), check if this is an open or closed circuit on the circuit loop - and then provide a little jumper wire across the solder points if it is a closed normal condition.
I was also successful in removing the switch off the clear plastic mount. I had to drill a little hole into the clear plastic just in front of the switch mount screw - and then with a little jewel screw driven, back it out thru the drilled hole. Then the switch comes off with a little wiggle and pry up off the additional clear plastic pin into the switch. getting it back on this way was tricky.
I recommend the desolder way
oops gotta go - making dinner for my girlfriend
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Great work: I've added your comments to the FAQ. Any more are most appreciated.
Steve
--
See the 700/900 FAQ at the drop-down menu above right.
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Definitely (please!) add Rob's excellent info to the FAQ.
I just tackled this last night. Rob's method for opening the speedo is *much* better than what's in the FAQ write-up here:
http://www.brickboard.com/FAQ/700-900/ElectricalSpeedometerRepair.htm
The problem with what's in the above file is when you de-solder the 4-pins to the speedo's magnetic coil windings (marked sin/cos). Much heat on those pins when trying to get the solder removed, conducts to the other end of the pins, and you loosen the ends coil windings off of those pins (which aren't very well attached to those pins). This is apparently what happened to me, as I discovered the windings hanging loose, when I did a post-mortem on what was an unsuccessful repair. At that point, the speedo guts are toast, because it's really just impossible to reattach them.
Rob's method avoids all of the risks, and it's easier to boot: Turn the needle counter clockwise (gently over the "peg" at 0mph) and pull the needle off. Then the four screws on the back of the speedo, and the two screws holding the odometer motor to the odometer assembly. Then just zip-tie the motor to the board (you don't want to wiggle the flexible circuit thingy too much). Then you replace the capacitors per the FAQ's instructions and specs. Just be careful with those magnetic coil windings!
Fortunately, I had a pristine spare speedo on hand, so I just swapped the guts into my original faceplate/odometer, and all is well!
Thanks, Rob!
-Ryan
--
Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sway Bars, GT Braces, Dracos
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars
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There is hope :-)
David D’Angelantonio’s file in the FAQ’s on capacitor replacement:
http://www.brickboard.com/FAQ/700-900/ElectricalSpeedometerRepair.htm
Below is a link to my post concerning similarities and differences of the 1991-1994 speedometers. It contains several errors in information.
It assumes the 1995 940 cluster is the same as the 1993-94 and that simply is not true. I can not provide any information on the use of the 1995 cluster in any other application.
It also suggests that the 1993-94 clusters are a direct swap to the 1991-92 cars. In a later post I added that the fuel gauge does not work when the later (93-94) clusters are installed in the earlier (91-92) cars.
http://www.brickboard.com/RWD/volvo/1371221/740/760/780/additional_information_140mph_speedometers_199195.html
In this thread I posted that Karl Nitz had found a work around to make the 93-94 clusters fuel gauges register properly in the 91-92 940’s:
http://www.brickboard.com/RWD/volvo/1382761/740/760/780/making_9395_instrument_clusters_work_9192_79_series_refuel_gauge_procedureimages.html
Good luck in your quest. Please report back what ends up being the fix that worked for you. Obviously these instruments are a weak point and all input is valuable in keeping our cars "fresh"
Randy
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there were some Extensive informational threads about this a few months ago. they provided remarkable detail, and I recommend you do a search for them. One I believe had '91 speedometer' in the subject line.
I know someone who has some spares, I believe the interchange you ask about will not fit, but am not positive.
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I'm just buying another GPS. (My cruise works).
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I am now successful in fixing both my 91 and 92 speedos in the last two weeks.
Replace all the capacitors per FAQ link. If you can't get all of them, them just get what you can at Radio Shack. Do the 220 micoF one.
Clean that board well with electrical contact cleaner. Get a toilet paper roll and cut a little strip to fit under the two IC's. Soak it with cleaner and clean under the IC. Clean between the IC legs.
Check all circuit paths for continuity with a DMM. Note the circuit paths are different on each side. It really helps to hold the board up to a strong light to see the paths. Check them for corrision damage. I had to jump one with a small wire from the 7th leg of the IC to a capacitor leg b/c the path was burned thru from capacitor acid.
I went thru and re heated all the solder points. Careful with to much heat!
To disassembly the board for access, twist the needle off CCW over the stop pin. (reinstall so it stops CW on the K at KM/hr. Desolder the Service light wires from the board. Unscrew the odometer motor and zip tie the motor worm gear to board where the ribbon is attached to the board. I did this to keep the motor from pulling on the fragile ribbon.
Remove the 2 screws towards the center. Not the ones centered between the speedo pins (those remain in place)
Get a small pen solder gun and if you need some solder for touch up.
Getting the cap's off is done by staggering the cap side to side as you hit each leg pin from underneath as the solder breaks from the heat. They will slowly walk off the board. Reintall in reverse. Strip side of a cap is negative! Get the polarity right. Make a picture of the existing cap's. Cut the new cap's legs so they are not so long.
I will tell you that getting the clock connector off the back of the cluster was a bitch. The two prongs don't give up. Get a little flat head to help pry them open as you pull. Bend them away so if you need to remove again it is easier.
The turbo hose is weird. I pryied mine off from the brass nipple out the back of the cluster. Just get a flat hear under the angle adaptor and work it off.
Please undue the battery! To prevent a short.
If you never took the cluster out, there is a white security clip on the 4 pin connector behind the speedo. It breaks so don't worry.
I can do this job now in my sleep after dicking with it so much
Thanks BB!
Rob
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