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92 Volvo 240 speedometer help needed

slasherz59

Member
Joined
Mar 25, 2010
Hey guys working through a speedometer issue here at work.... trying to save the guy some money ( he?s very hard to understand Haitian guy)

Car is a 240 92 came in for a bunch of issues and have worked through those...
but he is complaining of a no speedometer and no cruise fault...

He did some of his own work and ended up plugging in the brake light switch to the two ports in the back of the cluster covered by the rubber hose.... I know that?s bad but how bad? And what does it do? And what is it used for?

He bought another cluster a year ago and put it in. Same concern. With that one. Everything else works except the cruise/speedometer/odometer. (I don?t think he messed with this one but it?s hard to understand him) I have ubat on the feed wire and a nice waveform from pin1and 2 from the rear sensor that multiplies with speed and stops at a stop.

Kinda looking for guidance or tips as I haven?t messed with this specific issue much. I have not taken the cluster apart to check for any obvious issues but that?s coming. Again trying to keep costs down for this guy...

(I have had two other 240s in but they where too nice to borrow a part for a diag.... and my cluster at the house has a broken needle)
 
The 2 spades on the center back of the cluster with the hose around them are tied together and are the speed signal that goes to the cruise control box. I'm not positive, but I'm pretty sure that plugging the cruise control brake switch into those spades wouldn't cause any permanent damage.

A non-working speedo and cruise (and odometer) suggests that the signal from the differential isn't making it to the L or right-angle connector on the back of the speedo. (Another symptom of this is high idle after driving around for a while, that goes away if you turn off the car and restart immediately.)

See cleanflametrap's writeup on how to test the differential pickup signal to the connector, and how to repair connector pins:
http://cleanflametrap.com/speedoDiag.html
(Note: your '92 wires/colors will be somewhat different than the '89.)

You said "I have ubat on the feed wire and a nice waveform from pin1and 2 from the rear sensor that multiplies with speed and stops at a stop." Where exactly are you measuring these?
 
I agree with bobxyz to an extent. The cruise should still work even if the speedo/odo are broken. I would check for the speed signal coming from the rear. However, having a brake switch wire sent to the signal prong sounds awful. Depending on which wire he put there, the damage to the cluster and cruise module might be the death of both.
 
I'm not so sure plugging the brake light circuit into the tabs on the back of the cluster is survivable. The chip maker claims the output is "short circuit proof" while describing it as an open collector NPN output for the taximeter. This is what is used as VSS for the LH2.4 ECU and cruise control.

Many of us know the chip is damaged when the tach wire is mistakenly connected here. I've always assumed the "short circuit proof" NPN transistor was not designed to withstand the flyback voltage from the ignition coil. But maybe it can't take "ubat" connected directly to it either.

The detail can be found by searching the net for the data sheet on UAF2112.

Edit: The chip is UAF2115 not 2112. Can't depend on the biologic memory.
 
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When the OP said: "[the customer] did some of his own work and ended up plugging in the brake light switch to the two ports in the back of the cluster covered by the rubber hose...." I assumed that the customer had plugged the brake light switch wire from the cruise control harness into the cluster VSS pin by mistake. (It would be really strange if the customer decided to make their own new wire to connect the brake switch to the cluster.)

From the cruise control module, there's a single BL/R wire going to the brake pedal switches, and another single OR wire going to the back of the cluster (see TP30866-2_cruise_control.pdf). If the signal on the brake wire to the cruise box is open or +Vbatt, then cruise is disengaged. If the brake wire is plugged into the console VSS by mistake, the cruise box thinks that the brake is being pulsed rapidly whenever the car is moving.
 
For the sake of his two clusters, I hope your assumption was the correct one. I envisioned the two clips normally going on the brake light switch were put on the tabs on the back of the cluster, resulting in the brake lights being on all the time. I have no idea how difficult it would be to have those wires reach the instrument panel.
 
Sorry if I didn’t clarify.... he plugged the two brake light pins not the cruise control switch.

So the wires from the brake light switch are ubat(12v) and then to the bulb failure sensor. Both of those are female terminals that he plugged into the two male spades between 31 and 233 on the instrument cluster -the ones surrounded by the flexzilla like rubber piece (https://www.240turbo.com/240gaugewiring.html)

I was measuring the L connector on the Speedo I have ubat and waveform on the other two pins
 
This may help you trace the signal. Note the 92-93 unit has a separate ground for the differential sender and prescaler circuit, separate from that of the main odo/speedo circuit.

speedoDwg02.jpg


Some of the folks on here have replaced the 2115 chip after similar mistakes and saved their units.
 
OK, I misunderstood. Plugging both brake light switch wires into the back of the cluster will turn on the brake lights and will apply a continuous +12v to the VSS pin of the speedo chip. Even though the datasheet says that the VSS pin is short circuit protected, damage to the chip may have occurred.

Since you see good signals right at the L speedo connector, it sure seems like the speedo chip must be bad now. Before swapping clusters again, check that the flex fuse on the back is still intact (should measure ~0 ohms end-to-end). Does everything else on the cluster work correctly?
 
Hey guys working through a speedometer issue here at work.... trying to save the guy some money ( he?s very hard to understand Haitian guy)

Car is a 240 92 came in for a bunch of issues and have worked through those...
but he is complaining of a no speedometer and no cruise fault...

He did some of his own work and ended up plugging in the brake light switch to the two ports in the back of the cluster covered by the rubber hose.... I know that?s bad but how bad? And what does it do? And what is it used for?

He bought another cluster a year ago and put it in. Same concern. With that one. Everything else works except the cruise/speedometer/odometer. (I don?t think he messed with this one but it?s hard to understand him) I have ubat on the feed wire and a nice waveform from pin1and 2 from the rear sensor that multiplies with speed and stops at a stop.

Kinda looking for guidance or tips as I haven?t messed with this specific issue much. I have not taken the cluster apart to check for any obvious issues but that?s coming. Again trying to keep costs down for this guy...

(I have had two other 240s in but they where too nice to borrow a part for a diag.... and my cluster at the house has a broken needle)
So where do I plug the red and yellow one with the female spade end on it???
 
So where do I plug the red and yellow one with the female spade end on it???
I've got a 93 240 it was my daily driver like a year and a half and then it just said it was done driving for a minute. I put a fuel pump in tank and in line, water pump, the spark plugs the plug wires, distributor cap and distributor button, thermostat, number one injector was fouling out so I changed the injectors. She is still running kind of rough I took the tank off and had it vatted cuz if it's pretty bad I have not got her back on the road yet but I will get her legs back under her before it's all over this is mine I love this car.
 
my electric odometer gear pod is missing/gone. didn't notice it fall out on disassembly so i'm presuming that it's been missing for a while. but now that leaves me conflicted because my brick is a '92 245 super polar so i have no idea if it's 25 or 26 tooth gear. is there any way to find out? it's italian market if that helps at all.
 
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