Thank you for that info, everything's back to where it belongs including the yellow wire-double spade.

I've located a nice 1990 cluster that should work on my car, I dunno if $150 is a good price though. Its supposed to work but I have no clue of the sellers testing methods.

 

You dont need a whole cluster. Just a speedo. I would test your wires very well first before you throw a single dollar at it.

 

Got ya, and I'll be testing them sooner or later I'll make a different thread on them.

I really don't want to replace the speedometer, I know that the current mileage isn't accurate but I don't want to tack on an extra 100k.

 

Just buy one with 100k LESS than your actual mileage! jk.

You can use a pick and slide the numbers over to the left carefully and they freespool and you can change em. At least that worked on 740's....


Pierce told ya how to check your sensor and confirm wiring is good ALL THE WAY up to the speedo. start there.

 

I can do the "cleanflametrap" test tomorrow, hoooking up a modded 9V adaptor to the rear speedometer wires, that and I'll have a mullimeter to test on them.

I'd love to run Pierces test, but I wont have a second hand available until this weekend, and thats an if.

If you can drop the odometer numbers individually that would be nice, I'd probably set them at 122k.

 

I picked up a nice Millimeter I'll be testing out tomorrow, I don't have a second pair of hands so it'll just be simple stuff, I'll get readings from the back wires, maybe the cluster.

I really wish I could work on this thing more but my wagon double duties as a daily driver and a project.

 

Even a $5 harbor freight multimeter will do the trick. All you need it for is measuring resistance (ohms. The omega symbol), and for 12v voltage.

You can't "read" the signal with a cheap voltmeter, but you will be able to at least check that the wiring is good between the plug in your trunk and to the sensor at the diff. You would need a graphing multimeter or an oscilloscope to chart the waveform. Chances are it's fine and you just have a speedo problem. Much MUCH more common.

If you had problems with the wiring back there you would also have check engine light saying speedo signal and idle issues. Cruise control on this car? Does it work.

So all in all I bet you have a dying speedo, but instead of tossing $150 at a cluster, it is worth crawling in the dirt to unplug the sensor wires at the axle and do a couple tests first!

 

I dont have a local Freight so I hit a Sears for a $15 Multimeter, have a spare Harbor one but the sealed batteries dry.

My car has cruise control but it does not work, wont work with a dead speedometer. Idles great at 990 rpm, no CEL light.

Months ago I DID have a CEL light go off once and some idle issues, but re tensioning one of the plugs behind the speedometer sorted that out (after at least a dozen other fixes that didn't).

The wiring in the back isn't frayed but I'll test it tomorrow when the suns out, knowing that the meter must be at ohms will help me.

 

warmed up idle should be 600-700 rpm. 990 is a cold idle.

ohms is used for measuring resistance and continuity, and can only be used on isolated unpowered circuits.

powered circuits, you use the volts setting, an usually measure relative to ground.

 

Its probably lower when I'm driving about, I'll check next drive.

Thank you for the note on which setting to use.

 

If your speedo signal is missing, you will have idle issues. High idle after freeway speeds is what I saw.

That is what these forums are for! Learning. The learning curve is very steep at first. You start to know enough to be dangerous pretty fast!

 

For me my idle was always too low when in park, fine in gear, would sometimes stall out when I'd start the car. It was like the ECU wasn't aware that the car was parked or when the engine was cold.

Indeed, I know a bit about the engine but electronics are still kinda new to me.

 

Sounds unrelated. Maybe dirty throttle body.

The best diagnostic test procedure I have ever read is simply the greenbook process. I have always just created my own test scenarios, but sometimes I made it harder than it needed to be. This process walks you through how to test every input AT THE ECU. For example, don't be foolish like I have in the past and do coolant temp sensor tests digging deep under the intake manifold and probing an unplugged sensor. Another example this .pdf shows is to BACKPROBE ECU pins too. Dont go poking multimeter probes in sensitive ECU connections.

If you ever have problems with your 1989+ 240, use this process:

http://www.volvowiringdiagrams.com/v...20Complete.pdf



I am still learning electronics myself. I am at the point where i need to invest in a graphing multimeter/oscilloscope so I can test sensor outputs such as the RPM sensor and speed sensor.

 

A quick note I should mention, the previous owner who told me about the loose back wires mentioned that he couldn't get the air conditioning working. I did nothing to the AC, but yet it works really good for such an old car.

Thank you for the PDF, I've dug around and found my own cars ECU, its a newer white tag like you'd get on later 240s (usually '90 models got a pink tag one).

 

I like to test the Coolant Temp Sensor by unplugging the ECU and ICU and measuring the resistance at the harness plug pins. take the interior access panels off, drive the car til its nice and hot, park, shut off, unplug the ECU, ICU, take hot measurements, wait a few hours, take cold measurements. bonus points for using an IR thermometer to read the engine block/head temperature under the intake manifold where the sensor is, and plotting the Ohms/Temp values. the charts are in that book.

the Volvo OTP 240/260 service manual CDs have "Engine Management LH 2.4/LH 3.1 EZ116K 240 1989-1993", TP 32135/1 but its 256 pages and copy protected.

the 940/960 disk has mostly stuff on the 960's MFI because that was all new, but there's TP 32043/1, "LH 2.4 EZK 116K for 700/900 1989-", it covers the B200F,G,FT, B204E,FT, B230F,G,FT,GT, B234F,G" 'modifications to 1992 included'

I don't have the 700 CDs

 

But do you desheath the plug and backprobe? I haven't ever caused a problem front probing things, but good practice is to always backprobe so you dont bend the pins and cause a poor connection. When you pull the sheath, the pin numbers are printed right there too!

I have read everything from guys putting their sensor in boiling water to ice cream to test it! Ha. Not bad ideas, but too much work and wont tell you if you have bad wires or connections. Temp sensors barely ever fail. I have never had one fail. It is just where noob volvo mechanics start first whenever they have a hot or cold running problem. Logical to some degree, but probably NOT the issue.

I have spent years doing it the noob way. Doing tests according to that .pdf is the ADVANCED way of checking things. Glad I could help. Others have obviously helped me by linking me to it too.

My 1990 240 has a white tag with replacement VOLVO parts label on it. I am surprised if there are any pink label ECU's still working! jk, but only kinda....

At a minimum, the fuel pump priming circuit on them dies. I have a dead white label ECU in the garage. Primes fine, but you go to start the car and its dead dead dead!

 

no, I test the coolant sensor with it unplugged from the ECU/ICU, as I just want to measure the resistance of the sensor and verify the harness is connected well.

there are other tests where you peel back the shell and probe the outside. i use gold plated wire-wrap pins from electronics as the probes, and connect those to the meter with clip-leads like these...
E-Z-Mini-Hook? X100W Series - E-Z-Hook - Jumper | Online Catalog | DigiKey Electronics

 

Multimeter tessted, the rear wires from the sender have a base reading of 2.92


This weekend I'll see about getting a second hand for the wheel test.

 

was that 2.92 k-ohms or 2.92 ohms?

you /could/ take some lamp cord or whatever, hook it up to the speedo connector behind the instrument panel, and run it out the door far enough, hook up your meter to the other end of these wires, and spin the wheel with a foot while watching the meter in AC volts mode (put it in AC Volts, and if it has a range button, push that a few times to get a range that shows x.xx V). also if the meter has a 'Hz' frequency mode, spinning the wheel should show some number of Hz, probably a fairly small number at sane spinning speeds, this would go up and down with the speed of hte wheel.

oh, I believe the speed pickup is only on the right hand wheel, so jack THAT one up, leave the left rear on the ground.

 

2.92 k-ohms

I'll dig around my wires and see if I can find anything long enough, dose the wire have to be thick or just anything long enough to reach the connectors?