So I thought I must have dislodged a light bulb or something when, 3 years ago, I put a tach in my 87 244 (5-spd) and the upshift light no longer worked.

Did the same thing this week in my "new" 92 (also 5-spd). Hmm... new tach, works fine, but no more upshift light. Anyone shed some light on that?

Also, I was curious how it works- seems to observe a tach pulse in some way, and compare that to vehicle speed. I can make it go on and off by coasting at 60 in neutral and playing with the throttle. Above about 2500rpm, it'll turn on. The 90 740 has both an upshift light and a tach, so I was wondering why the 240 can't have both, or maybe I broke something both times! Could happen, you know.
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Rob Bareiss, New London CT ::: 92 244-M47-207K ::: 90 745GL-M47-268K ::: 88 245DL-AW70-230K ::: 88 244 SOLD! 87 244 SOLD! Still looking for a bright red or black 244 with sunroof...

That's the weirdest thing! I noticed the same thing a long time ago but forgot about it until now.

I'd love to know it's little algorithm for shift light display. I can't imagine it is particularly sophisticated.

I wonder if there is some defeat function or if the light just burned out or what. Not that this post helps anything but I just had a weird memory from long ago.

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Chris Herbst
Northern Virginia

Hi Rob,

The yellow/red wire that plugs on the corner .187 tab runs the shift indicator lamp. It comes directly from the ECU and shares no circuitry with the tach.

The ECU has the RPM information from the ICU without needing connection to the coil, where your tach goes for it. It also needs the vehicle speed info from the speedometer, which if missing, should set a 311 if I read the book right.

As many times as you've had clusters out of the dash I'm sure you reconnected that little yellow/red wire, but if you want to verify that end of it, grounding 26 on the ECU plug should light the upshift lamp.

Also, just a vague memory, but I seem to recall someone saying the ECU has to reconstruct its shift point table after being powered down, as part of its adaptive behavior. Does that sound crazy as it does to me?
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Art Benstein near Baltimore

Drive-In banks were established so most of the cars today could see their real owners. (E. Joseph Cossman)

Mmm, yes. No. I'm sure.

The red/yellow wire is indeed connected to the tab in the lower right of the cluster, as it was in my 87 as well. I actually had the back of the 87 cluster labeled for the placement of the couple of individual wires to it. I had that one out many times.

The 92 cluster, I'm sure is connected back as it was. But the upshift light doesn't function. I should connect a jumper to the light wire with an add-a-lug connector (my favorite spade lug in the whole wide world). See if the signal ever goes on anymore.

I need to get in there again soon, as one of my instrument lights seems to have died and also the rest of the dash illumination has crapped out. Not sure really if they ever worked but I know the right instrument bulb was working, and now it isn't.

Another investigation for another day I guess.

I don't buy that bit about the thing having to relearn shift points. It would be set to a certain value of the incoming RPM signal. I don't think these cars had any kind of adaptive electronics, but if they did, I guess it would be the LH 3.1 version.
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Rob Bareiss, New London CT ::: 92 244-M47-207K ::: 90 745GL-M47-268K ::: 88 245DL-AW70-230K ::: 88 244 SOLD! 87 244 SOLD! Still looking for a bright red or black 244 with sunroof...

LH 2.4 is actually VERY adaptable, and there is a procedure in the owner's manual to "retrain" the shift light if you interrupt power to the ECU.

Here's a quick LH 2.4 anecdote: I disconnected the battery when I changed the fuel pressure regulator as a precaution. When I reconnected the battery, the car would barely start, would run only with the throttle open, and the mixture was super rich. I thought I had missed a vacuum hose, checked everything and even swapped back to the old FPR, with no improvement. Then it hit me to disconnect the AMM. I did, and the car started, but ran as it should without an AMM. The idle was a bit erratic and the exhaust smelled funky unitl the car warmed up and the O2 sensor started giving its input. No OBD codes other than that for the "missing" AMM. A good, used, AMM made all happy again.

My theory: The original AMM was well out of spec, and the ECU apparently had been compensating for it. Disconnecting the battery cleared the memory, and with the fresh start, it couldn't figure things out with the bad AMM.

I really like LH 2.4. Simple, robust, and efficient.

-Ryan


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Athens, Ohio -- 1990 245, 128k, M47, E-codes -- 1991 745, 278k (girlfriend-mobile)

Hi Rob,

Yes, I was sure you had connected it too, although I tend to err on the side of more faith, estimating others' diligence.

I'm guessing your "add-a-lug" is for a .250 faston, and this is a .187, but it is gobs faster to get at the ECU connector than to pull the cluster again - that is why I offered the suggestion that would check the circuit back to the source. Also, the clue I offered about the VSS signal being necessary is worth checking.

Your instrument lights will probably die each time you bump the cluster; they are the newer halogen type, shockingly expensive, and extremely brittle when aged. FCP can provide you with the best prices.

I don't think these cars had any kind of adaptive electronics, but if they did, I guess it would be the LH 3.1 version.

Beginning with LH2.4, the fuel injection ECU is adaptive, although its memory is volatile compared with the Bendix (Regina) equivalent. All you need to do is remove fuse 6 or disconnect the battery for a second, and all modified fuel trim is lost. However, I don't know about specifically the shift point table - most likely because I didn't pay attention, not having any 5-speed cars.
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Art Benstein near Baltimore

The short fortune-teller who escaped from prison was a small medium at large.

Twice, after working on the problem with the blown fuse 5, and having had fuse 6 out to clean it up, I've gotten a single, one-time only stall out of the car. Usually around the first stop sign or red light, where it has been running 1 minute and now must idle.

Restart without hesitation, runs completely normally after. But each time it did it (twice) was after pulling fuse 6. Coincidence? A day or two later, haven't had any repeats of that. Go figure.
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Rob Bareiss, New London CT ::: 92 244-M47-207K ::: 90 745GL-M47-268K ::: 88 245DL-AW70-230K ::: 88 244 SOLD! 87 244 SOLD! Still looking for a bright red or black 244 with sunroof...

Probably a "relearning" thing, since for every 1990-on 240 built after my car, one of those two fuses will clear the computer's memory if removed. I forget which!

-Ryan
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Athens, Ohio -- 1990 245, 128k, M47, E-codes -- 1991 745, 278k (girlfriend-mobile)

According to the Bentley diagram on 390-62 (Grid L-3), the shift indicator light (111) Y/R wire has a nearby(?) connector with either a contining Y/R wire to the Auto OD relay — or VIOLET wire to ECU 26, like Art said.

I don't see anything showing how connecting the tach to coil#1 could affect the 111 indicator circuit.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hi Bruce,

That yellow/red wire was the subject of curiosity for me before. It is used for both purposes - shift light on the 5-speed, and OD-off light on the automatic.

The violet lead is a jumper to ECU-26 which is a harness difference in the manual tranny cars; taped and folded back on the automatics. I suffered a previous tech's mistake (89 245) where the violet wire was thought to have fallen out of the connector (instead of purposely left out and taped) and "replaced". That causes a resistor in the shift indicator circuit of the ECU to char the ECU circuit board when the OD is not disabled.

There were a couple manual to auto conversions of LH2.4 240s done by brickboarders, so I have posted the warning about the harness differences before, but I think in both cases the OD relay circuitry was not included among the AW-7x transplants. Because LH3.1 appears to be only a 5-speed thing in 240s, its harness must be shared by both.

Further checking on another 89 (properly taped) and a 91 revealed Volvo had changed the harness (by 91) to place the violet "jumper" in a less obvious place behind the instrument cluster, instead of in the plug above the fuel injection relay as on the earlier cars. I suspect the 92's violet jumper is where the 91's was found.




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Art Benstein near Baltimore

"He has Van Gogh's ear for music." Billy Wilder

Very interesting to learn about the difference in wiring harnesses between manual and autos!

The upshift light hasn't worked in my car. The red/yellow wire was not installed on my 1990 5-spd 240's cluster, but it is hanging around in the dash. I, too, had assumed it to be for the OD light (that's what Bentley says).

I'll plug her in next time I dig into the dash! (a weekly occurance it seems...)

-Ryan
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Athens, Ohio -- 1990 245, 128k, M47, E-codes -- 1991 745, 278k (girlfriend-mobile)

Hi Ryan,

I'm glad to read about the owner's manual note on retraining the shift light. Guess I should have trusted my recollection, but I could never have cited the source without your input. Thanks!
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Art Benstein near Baltimore

A grenade thrown into a kitchen in France would result in Linoleum Blownapart.

I don't know the answer, but I've researched this a little.

The '92 light is supposed to be turned on by the ECU, which has both crank sensor and Speedo inputs and (I think) a throttle-closed input. I have a '93 ECU in a manual car, and I can't get it to turn on the light, at least not yet.

The '86 light is supposed to be turned on by a separate, unique relay. The '86 ECU has no speedo input. I had an '86 with an added tach, and the upshift light worked properly.

I believe the '88 follows the 86 approach.
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jds