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What actually tells the OD to engage (AW71)?

Three Fat Tigers said:
I assume you know how to read a factory wiring diagram?

Sure'nuff!

Oh, so close! But you still missed.

If all that happened was like your lil' ole red crayon showed, that overdrive would never disengage, and there's only be two shifts, with a real leggy 1st gear like I described. Reverse would be a real trip as well. But that isn't how it happens, is it?...

Darn that pesky transistor in the relay box and those dangling wires that you ignored! Those things keep that solenoid from engaging until the car's in third gear. Shucky darns, no power to the solenoid until then.

We're making progress though! You seem to have realized now that the AW71 isn't the fourspeed gearbox you claimed earlier, and you've figured out it really does have an overdrive. Pretty soon we'll have you up to speed on it!

For bonus points, see if you can find any problems in that diagram of yours that you scanned. I'll give you a hint for one of them, has to do with a series circuit.
 
Damage Control Mode

foxtrapper said:
If all that happened was like your lil' ole red crayon showed
That's not my red crayon, that is Volvo's red crayon. Ok... so in the face of documented proof that you are wrong you deny the facts. On the point about it not being a 4 speed, I am aware of the technical aspects of this transmission, and have been since long before you were born. You still cant deny it has 4 speeds, and can be referred to as a 4 speed transmission, maybe not technically, however I wasn't in super saiyan technical II mode when I responded at that point in this thread, perhaps you next will turn your attention to how I leave out the apostrophe in the word dont, just make sure your power level is at maximum if you hope to make a dent in my armor. You clearly have a bizarre understanding of how this transmission works, and I'm not very interested in damage control.

trunksthing.gif

Suggestions:
Hey foxtrapper, why don't you go back to the brickboard which is where your accent is obviously from, or stfu, as you are obviously are a freaking idiot.


Ok so now somebody ban us both so I can get some sleep.
 
I appologize TFT, I accidently gave you too much credit. Didn't mean to upset you by doing that, truly. :roll: I really thought that you'd traced the circuits yourself, thereby actually following them and thinking about them while you did it. I was really quite impressed.

I was hoping that with some nudging you'd have noticed that the ground side of the relay coil is switched by a transistor. I figured you missed that when doing the red lines, since it's not common and the significance of it is easily overlooked. For it means having juice at the coil won't activate it unless the ground switch is engaged. That's why the solenoid isn't permanently engaged like you think. Power is available to the relay coil, but only when the transistor gets the signal does the unit ground, thereby energizing the solenoid and engaging the overdrive. That's why it only engages when the transmission engages 3rd gear (didn't someone mention that earlier in this thread? I'm sure I saw it somewhere).

I was also hoping you'd notice the problem with the dashboard light and solenoid being in series as drawn. Think about it.

So now you're spinning this weird notion of me denying facts? :???: I'm not the one insisting there is no overdrive in an AW71, that was you. And I'm not the one insisting that the overdrive is permanently energized. Hmm, unless you're claiming 1 2 and 3 are done with the overdrive engaged, and then it turns off. And I really hope you're not going to start insisting that grounds aren't necessary for electrical circuits because of the red lines in that drawing. And please don't say factory manuals are 100% perfectly correct at all times.

I've tried keeping it light and humerous. That's what the tongue in cheek aproach was for. :-P For I could see by your writing style that you're not the type to handle corrections well. Lighten up my little pudgy kitten (intentionally humerous jab at ID). Life is too short to take yourself so self righteously. Live and learn a little. You're not as omnipotent as you think you are.

As they say back ole Meheco; amf.
 
Damage Control Mode

Well you are simply wrong, and it's still crystal clear that you do not know what you are talking about, have no direct experience with this circuit, and are unskilled at reading wiring diagrams.

I have used Volvo OD relays extensively for a wide variety of applications other than transmissions. The default mode (when power is applied to terminal #15 & ground to #31) of the automatic type OD relay is on, that is to say the coil is grounded via the internal logic circuit and the relay contacts are closed. The manual trans OD relay does exactly the opposite. But don't believe me, take an OD relay bench test it for yourself, something you have obviously never done. You can even see this clearly in the diagram above for when power is reaching the solenoid, it is also reaching both legs of the OD indicator lamp and is therefor not lit. If your theory was correct then power would not be reaching the solenoid, and not reaching both legs of the indicator lamp and the lamp would be lit (as it grounds out through the solenoid) whenever the solenoid was not powered, and as everyone who drives an automatic Volvo knows, the light is out at all times unless you manually turn it on (thereby deactivating the OD relay), the indicator lamp is not lit through the first 3 gears and the goes out in 4th. Unless you manually toggle off this relay via the momentary push button, it remains on at all times, it does not just turn off for 4th, it also does not just on for 4th, it is always on. If you will also note, there is no input to the relay that could tell it the trans was in 4th.

foxtrapper said:
I really thought that you'd traced the circuits yourself, thereby actually following them and thinking about them while you did it.
Been doing so all along, when are you going to start? You are defending a position that is indefensible in the face of the factory diagram I posted, anyone who can read a diagram will know this, and idiocy will not win out over facts. And as for tung and cheek, the tone of your response above was snotty, not humorous.

I'm not a baby sitter, I suggest you find someone else to wipe your nose for you.
 
I think Foxtrapper needs to learn how to help without being a jerk; he came close but thought he was really smart and might as well take a shot at someone else who was trying to help. Three Fat Tigers is one of the most helpful maintenance and repair people here and is almost always right and would freely admit he was wrong if that was the case.

Foxtrapper may have read some books somewhere, but he has not studied the wiring diagrams or, if he has, he does not know how to read them. And he certainly has not been under the car with a test light. Give it a try. He does not even have to be able to read wiring diagrams to do that. I think he needs a large slice of humble pie.

Philip Bradley
 
Geez... all this on my account?

It was the solenoid. I swapped out a $5 JY solenoid. I bench tested the original and it wouldnt activate, but the replacement fired right up thanx TFT.
 
Time to eat crow

*cough* Time to eat crow: well it appears I've unintentionally reported incorrect information over the past years in several posts (including this one), specifically relating to a singular point regarding the operation and function of the automatic trans OD dash indicator light on '85+ Volvos (white OD relay, 200/700/900 series). I've found that I have miss read the wiring diagrams on this point: Where I have reported that the OD dash light is grounded through the OD solenoid, it is however in fact grounded via the relay.

One leg of the OD relay light is powered via the ignition switch, and so is hot whenever the ignition is on. The other leg of the OD light is connected to the OD relay via terminal #87a, which is connected internally at all times to the #87 terminal used to supply power to the OD solenoid. When the relay is on, power is supplied to #87 & #87a, and because the OD light sees 12V+ on both legs, the light turns off. When the relay is off, power is removed from #87 & #87a, and I has assumed and miss read that there was no other connection at that point, thus assumed the lamp had no other ground but through the solenoid, I failed to notice that with the relay off, terminal #87 & #87a were connected to terminal #31 (ground). My assumption was also based on advice from my friend who has worked on thousands of Volvos over the years, and who is also wrong on this point, this is not an excuse though. The truth is clear as day for anyone to see in the diagram above, if one looks :oops:

This is not however true for the '84 and earlier 240 type OD relays (orange relay), which are the type I have the most experience using in my own circuit designs, where there is no internal connection to ground, but also the '84 and earlier OD light is always grounded, and is powered only by the OD relay when the relay is off.

So anyway in relation to this singular point regarding the OD light operation, I sincerely offer my apologies to foxtrapper and all who tried to diagnose related issues via my instructions.
 
Or Dremel it yourself (use the damaged solenoid) and buy your wife some flowers and yourself some six packs with the money you saved :wiggle:

By the way, nice thread I learned a lot (again).

Picture from TheLostArtOf.

Photo072.jpg


Picture from TheLostArtOf.
 
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Wow, please don't delete these post, I need to keep reading this thread to understand the correct answer, learn the wiring diagram, read this thread again, fail, buy a bunch of parts, fail and then read this thread again. I am doing it right?

I now officially have two cars with similar issues.

1). My 1993 245 is shifting through the first couple of gears and then just revving higher and higher! OD Light comes on and off but has no affect on drivability. I may just buy the IPD bypass kit? I think it could be the fact that the white wire that runs from the OD Solenoid to into the tranny tunnel and up into the car before it connects to the wiring harness has a bad connection? If I buy the bypass kit, that white wire doesn't matter obviously and I can simply disconnect the relay permanently without any battery draw issues and what not.

2). My 1992 today had its OD poop the bed, drove the car 20 miles after work parked it, then got in to go home and reversed out of my parents driveway and the shifter wouldn't go into drive, the shifter seemed jammed in neutral. Finally somehow got it to go into drive and for some reason the OD light wouldn't turn off the whole trip home. Once I got home I checked the fuse, it was blown, so I replaced it. After replacing the fuse, the OD light would toggle on and off again. However when I tried to shift pass (D) Drive into (2) the fuse would blow again and I can't seem to shift the tranny into gear (2) and gear (1) on the shifter while shifting out of park. Now over the last two weeks I have noticed that even after warming the car up for 3-5 minutes in the morning, it takes the car about 1/2 miles to feel like I can actually drive past 10 miles an hour, anything else feels like I have jammed the car into neutral until it finally chirps into normal operation (yes of course I always take it easy onto the car until it warms up, this is just way fussier then normal). Finally this happened today............. and the car doesn't seem to be shifting through all the gears as it normally does (@ ~ 20MPH, 40MPH, 60MPH).

Now I have two cars with similar issues and no where near the technical intellect or know how that 'Three Fat Tigers' has. Dive into the books I will!
 
Very impressively written! Unfortunately, it's completely wrong.

The ZF transmission is the 4 speed unit. The AW transmissions (both the 70 and 71) are conventional 3 speed planetary geartrain units. They are just like a Ford C-4, or a GM Turbo 350 in their 3 speed planetary geartrain design.

A separate overdrive is used by the AW71, and inhibited in operation to only third gear. This overdrive lives within the transmission case, but is distinct and separate from the rest of the transmission.

The electrical circuit to the overdrive solenoid on the transmission is not normally energized, it is normally off. It is only energized when the solenoid closes the contact, providing electrical power. This event only happens when the transmission is in third gear, and the shifter electrical switch is closed, causing the relay to close. Then, and only then, is electrical power provided to the overdrive solenoid, engaging it.

If the overdrive unit were to somehow "hang up" in the engaged mode, the transmission would no longer shift to four distinct gear ratios, but would engage only the conventional three, at the higher overdrive enhanced ratio. This would be most noticable in 1st gear, as it would be a much taller ratio, resulting in substantially slower acceleration.

I hope this information helps you to understand how these transmissions and overdrive units actually operate. Further information on this subject can be obtained from a factory service manual, wiring diagrams, and examination of the transmissions themselves.

My od button quit doing anything and 1st gear is so sluggish all the sudden...this explains it perfectly! I was wondering why it was so slow all the sudden in first...seems like I can do like 45mph in first and 70 in second with no problem but it's slow off the bat it's so weird.
Edit...also I only notice "3 gears" it's a trip
 
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