[Hey, Moderator: how does one do linked text to an ftp server? Your software tacks on an extraneous "http://" in front of the "ftp://" link, and removes the colon from "ftp://", changing it to "ftp//"! This software needs spanking. I don't want to host all my existing ftp pics on an http server. Sorry, folks.]

Just in case someone is about to have their old A4LD rebuilt for these symptoms . . . Maybe this info is common knowledge, but I didn't run across it in a cursory search.

[long story follows; for the summary, skip to the bottom.]

I have an '89 (my daily driver). I recently picked up a '91 (or maybe late '90, the numbers vary) with a toasted '88 trans installed. I also bought another '89 for parts a while back, and I had driven it before scrapping it: it had a good trans, which I stashed.

OK, when I bought the parts '89, it didn't run but was supposed to. I dragged it home (ftp link doesn't work, copy-n-paste this one: ftp://asavage.dyndns.org/Aerostar/89-89_Aerostar_01.jpg ) and after replacing the dead TFI module, it would run OK on starting fluid, but the ECM was dead, but by then I knew why: the alternator was full-fielded and was overcharging badly, over 18v. That had fried the TFI module, the fuel gauge, and the ECM. OK . . .

So, I pulled the ECM from my driver '89 and installed it into the parts '89 (I was very worried!). That got the thing running, and I could drive it around. It ran OK but had no 3-4 shift (OD) and no torque converter lockup, but since I only wanted the engine as a core (and some other minor parts), that was OK with me. I figured I'd done OK.

The problem came when I put the borrowed ECM back into my driver '89: now it also had no OD or lockup! Oh, no!!!!

I'm an old electronics bench tech, and by this time I figured I'd have to just bite the bullet and buy a used ECM (not too expensive), but since I had nothing to lose . . . I opened it up. Armed with the ECM pinout, the drivetrain wiring diagram, and my stereoscopic headset for the closeup stuff, I found two driver transistors smoked -- open, not shorted. Hmmm. Did an ohm check on the parts rig's transmission connector, and the two solenoids read near shorted (should be around 22 ohms each). Oh. So the bad alternator also shorted the tranmission's solenoids (?) and that fried the driver transistors. Hmmm. That implied that I might be able to replace the shorted solenoids and pick up a spare A4LD, at the expense of having to buy another ECM for my driver '89.

But wait!
I took the cover off the fried ECM from the parts '89 (keeping this straight?) and it too had fried trans driver transistors (no surprise there, eh?) as well as other fried stuff, but the good news is that there are FOUR identical transistors used for various things, and there are two non-fried transistors.

[Now I'm wishing I'd written down the transistor numbers & locations, and taken a couple pics, but I didn't.]

So, I robbed two transistors from the fried ECM and repaired my driver '89s ECM, and now I had OD and lockup again. Whew!

Still with me? Good, because here comes the part of the story that makes reading this far worthwhile.

So I go and buy this '91 with the dead trans, thinking I'll put in the "spare" '89s trans that I just diagnosed as needing a pair of solenoids. I got a good deal on the '91 I thought, since as well all know, there are NO good A4LDs out in the field, they all go bad it seems. I was planning on robbing the solenoids from the '91 to put in the spare '89 trans. Talk about cheap!

First problem: the trans in the '91 is from an '88. The '88 didn't use a solenoid for OD, only one for lockup: the ECM doesn't have control over the 3-4 shift in '88 like it does in '89. Dang! Not only that, but the '88s connector has only two wires because of this, and the idiot who butchered the '88-trans-into-'91 did it by using the '88s connector and just taping both the OD and lockup wires together. So the ECM turns on either OD or Lockup, and the trans goes lockup. And I'm missing the correct 3-wire male connector to mate to the trans. $h#t. Another trip to the junkyard (since I'd already scrapped the parts '89 and couldn't, therefore, cut it off of it) and I had the connector.

So I've got the spare '89 trans on the bench, pull the lockup solenoid from the trashed '91 ('88) trans., and order a new OD solenoid from NAPA. When it came in, I went to install the one-new and one-used solenoids to the spare trans. They are a bit of a pain to replace because you have to remove the valve body and one servo to do it, but it's not too bad when the trans is on the bench and upside-down.

However, when I hooked the solenoids up and bench-checked them, they both read shorted. Whoa!

Here's the reason:

• Shorted connector & solenoids(ftp link doesn't work, copy-n-paste this one: ftp://asavage.dyndns.org/Aerostar/A4...nnector_01.jpg )
• Bad connector! Bad! (ftp link doesn't work,copy-n-paste this one: ftp://asavage.dyndns.org/Aerostar/A4...nnector_02.jpg )

The plastic connector itself was shorted. I cleaned and cleaned and it looks pristine. No burned marks, no corrosion, nothing.

So I ordered a new connector from Ford (not having a spare: the '88 trans was only two-wire) and after assembling it shifts perfectly. I didn't have to buy the OD solenoid, but I'd already opened the package so I owned it.

Summary: if you have no OD (3-4 shift) and/or no torque converter lockup, it might not be a mechanical failure. It could be

1. Fried (open, in this case) driver transistors in the ECM ('89-on only)
2. Defective solenoid (shorted, open, plugged)
3. Shorted solenoid(s) connector!

More solenoid info here. (ftp link doesn't work, copy-n-paste this one instead: ftp://asavage.dyndns.org/Aerostar/Tr...Solenoid04.png )

Regards,
Al S.

 

Well done Al! I found that a very interesting bit of sleuthing on your part. A lot of time and effort preceeded your post and you should be commended for this contribution. Electronics baffle me, so I really appreciate your expertise in this field. You may be the only one in the country who would devote this amout of time and effort to diagnosing the A4LD in this manner. Just outstanding!

 

It's too bad that I can't make the ftp links work . . . even copy-n-paste doesn't work, because the forum software shortens long URLs by inserting "...", and it prepends everything with a "http://". I have both an ftp and http server, but I tend to keep most of the misc junk on the ftp server, and it's not unreasonable to have the forum software respect an ftp link to a picture.

Oh, well.

Mostly, I wanted people to know that a bad connector to the solenoid(s) can masquerade as a bad solenoid(s), and if any of the three things short, it fries the associated transistor that drives the solenoid. All of which can be repaired. Wish I'd taken some pics of the ECM's guts, but I was PO'd at the time.

Regards,
Al S.

 

I believe you can keep your links functional by enclosing them in tags, [URL...] [/URL...] (take out the dots and put the address between the tags) ex. [URL...]http://www.herringtontech.net [URL...]

 

Al, this was a recently posted problem that rlmdad and cooper did some remarkable online diagnostics to arrive at a similar conclusion - that the solenoids were shorted out but no one was sure why this would have occurred. It would seem your efforts have unlocked the source of many of these problems - a faulty, overcharging alternator. Here is the link to the recent post. It's a long one, but the key findings are within the final two pages. https://www.ford-trucks.com/forums/s...3&page=4&pp=15

 

Works for an http:// link: http://www.google.com.

Doesn't work for an ftp:// link:
ftp://asavage.dyndns.org/Aerostar/Ae...ge_Trailer.jpg

Both are valid links in the "real world" (whatever that means to you) but the forum software butchers the ftp:// link by prepending an "http://" before it and neutering the "ftp://" to "ftp//". Not nice.

It also URL-encodes the colon, the slashes, and all underscores. Blech!

Anyway, to actually see the ftp link above, click on it. It'll run through ford-truck.com, get redirected to a bad URL, and you'll get an error page (from my server) saying that it can't be found. The error URL will be:In the address bar, edit that to remove the leading "http://", then add a ':' before "asavage". That turns it into: and that will work. Whether it's worth the work or not, I'm not sure. The trailer is kinda cute, though.

Regards,
Al S.

 

On mine, neither solenoid was actually shorted; it was this connector in the transmission body that had the short: (copy-n-paste to your browser's address bar)Close-up view:I could have reused both solenoids, but I'd already opened the new OD solenoid's package, so I went ahead and used it.I don't exactly know how that van got into the condition it was, when I bought it. The things that were fried that I know about were: TFI module, ECM, fuel sending unit. After I replaced the TFI and used my other ECM, it fired right up, but anything above idle and the system voltage was pegging the dash gauge, even with the headlights and blower on. I disconnected the alternator at that point so I could test-drive the van to ascertain the condition of the engine & trans, and that's when I found that the trans wouldn't shift to OD, nor would the TC lock. I didn't think anything of that at the time. When I parted out the van, I sent the alt. to the parts store and they verified it was a fried regulator, so I sent it to my local auto elec. rebuilder as a core (and got a "Thanks!" from him).

The ECM, it had other things toasted besides the two transmission solenoid driver transistors, so it was running and operating when those two died. Personally, I suspect the kid had hooked up the battery backward, and that the connector body (remember, this is the connector shown in the link above, which resides in the transmission body, NOT the part that plugs into it) was shorted prior to that event.

What makes me wonder is how that connector shorted. It doesn't look like it got hot, the solenoids can't draw that much current. I suspect a design or QC flaw. I don't think that I kept it, so I can't do forensics on it.

The main thing I wanted to document, for anyone else who has an early (two or three wire connector) A4LD with a 3-4 or lockup problem, is that if you don't run through the diag procedure first, and just replace the trans, you might still have a problem: in the ECM. You have to have 12v on the center wire (three wire connector) at key-on time, and ground on both other wires (three wire connector) at 60 MPH part throttle (ie wheels off the ground, or long test leads and a road test). If you have power to the solenoid(s) but the ECM doesn't ground them at high speed, the ECM or associated wiring between ECM and trans is bad. And if the ECM is bad (not grounding the solenoids), replacing the ECM might fry the new ECM (which is what happened to me, because when I swapped in my ECM, I didn't know that there was a short on the line to the solenoids). In my situation (non-running vehicle), I really didn't have another way to go, but if yours runs and you only have a trans shifting problem, the whole electrical shebang is easy to test.

IOW, no point in replacing or repairing the trans if the ECM has become fried, and I've found at least one reason why the ECM fries: shorted trans body connector, a non-obvious culprit.

Whether the overcharging alternator had anything to do with this is still an open question. Personally, I vote no: I think that's a red herring.

Sorry about this long-windedness, I can't seem to get concise tonight.

Regards,
Al S.

 

asavage, I've got a message in to the website gurus here to see if it's possible to post an ftp link.

 

Post a link to your website home page then display the images or ftp link there. I have tried several things and the forum software does not allow the link. I had a ton of images on a site and they were all available with a simple http link. Your "code designation" workaround seems to work.

 

In case anyone's interested, here's a marked-up partial wiring schematic of the solenoids, 1989 to whenever the A4LDE came online. For 1986-88, there is no 3-4 (OD) solenoid.

(copy-n-paste to your browser's address bar)

 

A++ sleuthing.

Ken

 

2 LED's and 2 series current limiting resistors and one has dash OD and TC LU indicators
4R series also has trans connector circuits for same plus a volt meter on tranny temp sensor circuit and one has a tranny temp dash gauge

 

I like the TCC & OD indicator idea. Can you spec the resistor value?

Related: I would like to install one or two miniature switches. One to ground the TCC ECM line (holding TCC locked), the other grounding the OD line (holding in 4th).

The EVTM says the solenoids' states are ignored below 30 MPH, in case I forget to un-ground them. I used a similar setup on an '83 700-R4's TCC on a diesel, in order to get off-accelerator engine braking (credit here to Dad for actually doing the work on that rig). It worked very well: TCC remained locked at hwy speeds, and pulling out of OD on a downgrade gave very good engine braking.

I see mention in the EVTM about fault codes

• ON-BOARD DIAGNOSTIC TROUBLE CODES 86/566 SS 3-4/4-3 SHIFT ERRORS
• ON-BOARD DIAGNOSTIC TROUBLE CODES 89/626 TORQUE CONVERTER CLUTCH CIRCUIT FAILURE

A) Has anyone added manual grounding toggles to a pre-96 A4LD?

B) Am I going to set fault codes doing this? (correlative Q: what does the ECM sense when it senses something at fault in this circuit?)

 

Use Ohm's law to find resistor values:

Most LEDs can be safely driven with 3 volts at 20 mA, so you need to drop from 14 volts down to 3V, or 11V at 20 mA. V = A*R, R = V/A = 11/.02 = 550 ohms. Or 500 ohms is close enough.

How do you get engine braking with a diesel engine? Do you have a Jake brake?

 

Kinda reminds me of the guy at my tranny shop. He came across a problem that nobody had figured out in all these years, and so he decided that rather than swapping the whole valve body, which is what every one else would do, he was going to find out why. Basically, what seemed to be happening, was it felt like it was engaging second gear on takeoff if you put the shifter in the OD position. In drive it seemed to work normally. Once it reached a little more speed, it felt as if it dropped out of 2nd, into first, and then shifted back into second. Now heres the kicker, sometimes when this happens, you add a pressure boost valve and the problem goes away. Basically what is happening is that the modulator need wears into the soft aluminum casing, and the boost valve is basically a unit that is inserted into that opening after it gets enlarged by a machinist. My mechanic had found several transmissions he had worked on that behaved in the same manner. Occasionally, this didn't work and this stumped him. In my case, the boost valve had no effect. Now most mechanics at this point would just keep swapping parts till the issue went away, or until they just admit defeat. But he kept looking into it and digging through his schematics until he finally figured it out. Basically what felt like starting out in second gear was actually starting out in first gear, with overdrive engaged. There was a leak between the first gear circuit and the overdrive circuit, so if you had the shifter in the overdrive position, it would engage overdrive on top of 1st. At this point he explained to me that the 5 speed transmission does just that, but the computer controls it. Same with the newer 6 speeds, they stack OD on top of 1st, 2nd, and 3rd.

Anyway, didn't want to hyjack this thread, just thought I would share my experience as well.