Help! We just had our first snowfall, and noticed our '93 aerostar AWD seemed to have awful traction. Took a look from the outside and noticed only the rear wheels spinning, and you no longer hear that usual thump as the front wheels engage a moment after the rear wheels spin. No blinking 4WD light on the dash, even though it does come on for a moment when you start the car. No other noises or other symptoms either. Could of been like this all summer, just noticed it now when we got some bad weather. Any ideas? Not sure where to start with no blinking diagnostic lights. Thanks in advance.
Randy

 

Randy,
Hmmmm, well, if the AWD light comes on and then goes out, the system has supposedly checked the continuity of all the sensors and the transfer case clutch coil.
There are a couple of possibilities...
First, the control module itself is bad. This module does the "testing" and also the generation of the "codes". I'd start by disconnecting the module (its located under the driver's seat) and doing a pin by pin check to ensure the sensors, etc are all OK. If all is OK, you could replace the module with a known good unit and see what happens.
The fact that you haven't heard any unusual noises leads me to believe that you have not broken a transfer case chain, u-joint, etc.
It is possible that the transfer case clutch is mechanically stuck inside the case somehow... if so, you wouldn't get any strange noises nor would you get an error code.
Let us know how it turns out.
KenP

 

I noticed this while trying to back up my parents snow covered driveway. When I "babied" it, the rears just spun. The second try, I gave it a bit more gas and the fronts dug in and away I went.

 

Make sure the fuse for AWD is okay. I don't have my manual handy, it might be lumped in with the cruise control fuse.

Pull engine codes to make sure you do not have bad (wheel) sensors.

Check the fluid level in the transmission and transfer case.

Check the front drive axles and see if you can turn one with the vehicle parked. If you can, that CVJ is nuked.

Put driver's window down. Turn engine off! Jack up the front of the vehicle both sides under the control arms, set parking brake, chock rear wheels on front/back of tread so it can't roll forwards or backwards, van in Park.

See if you can turn the either front wheel.

Now, put in N, turn the wheels. When you turn one, the opposite one should rotate the other direction. Is your front drivehsaft turning while you are doing this?

 

Randy,

Were you able to remedy the AWD problem that you described in your posting? I've just encountered the very same problem on my '93 Aerostar, exactly as you described it. The 4WD drive indicator light comes on momentarily when the van is started, then goes out with no follow up fault code flashs yet the 4wd is not working. I too have no idea how long it's been that way since we just had snow the other day and it reminded me of why I would never buy one of these vans without AWD!!.

I did check and the 15A fuse was blown. I've replaced it and it doesn't blow until I encounter slippery conditions. Then the fuse seems to blow when the system tries to engage.

Please let me know if you came up with the problem. I was about to try testing out the control module and trying the procedure that was recommended to you...jacking up the front end and spinning the wheels, etc.

Thanks.

Dennis

 

Sorry, I have not replied back till now, with Christmas and all, I've been buried with other things..........but my Aerostar AWD just seemed to start to work again, right after I wrote my original note! Not sure why, but I suspect something in the transfer clutch was not engaging, similar to what Ken P. mentioned, and has somewhat started to work again. And I'm not really sure it's 100 % yet, but my wife has been driving it and says it fine, so who am I to argue? Looking at the owner's manual, it mentions that the front wheels are engaged about 1/3 all the time, until slippage occurs at the rear, then the fronts fully engage to evenly split the power. I suspect we're getting that 1/3 full time(which why it seems fine in minor low traction driving compared to RWD only), but I really don't hear that solid sound (thunk) of the fronts engaging when you intentionally spin the rear wheels on ice, like it use to, so I can't say it's really fixed yet. But I did check my fuses and none of them were blown. Thanks for all the help and advice, though, and I am going to check my front end, soon. It seems I'm not the only one with this problem, so any new advice is always appreciated.
Randy

 

Ken,

I read your suggestions to Randy a few weeks back regarding the problem with his '93 Aerostar 4WD van that would not engage the front wheels in snow. His problem seems to have cleared itself up but I have the identical problem with my '93 that became apparent during last weeks' snowstorm here in the east. I have no idea how long it has been this way but I found that the fuse for the 4WD system had blown. After replacing it, the 4WD light comes on briefly when the van is started and then goes out, as it should, but it does not flash any fault codes. During repeated starts and stops of the engine and driving on dry pavement, it appears to work OK until I encounter conditions where the rear wheels slip...then I immediately hear the fuse pop. Something is apparently causing a short when the system gets the signal that there is wheel slippage and it tries to engage the electric clutch inside the transfer case.

Using the Factory service/diagnostic CD program, I've run the series of electrical diagnostic tests of the wiring harness, speed sensors, 4WD lamp, NDS, and brake light switch. Some but not all indicate that the problem may be the control module, however there was a test of the E4WD clutch where you disconnect the module from the harness to verify that the clutch coil is engaging by jumping across pins 8 and 14 and grounding pin 13 and then driving the vehicle. As soon as I started to drive (only a few feet!), the fuse popped! This leads me to believe that the problem may not be a bad control module.

I've not heard any noises indicating that something has broken inside the transfer case. I jacked up the front wheels and with the van in Park, I can turn one wheel but the opposite wheel and the front driveshaft do not turn. When I put it in Neutral, the wheels turn in opposite directions as they should and the front driveshaft turns, which I believe is correct. I've also checked the oil level which is fine.

Since you seem quite knowledgable on this issue, I'm wondering if you have any other suggestions I might try? I'm determined to figure this out and repair it myself rather than caving in and taking it to the dealer! Any help would be appreciated.

Thanks.
Dennis

 

Dennis,
Hi. I think you're pretty close to the problem...
Looking at the circuit, you know that pin 8 is +12volts battery power.
Pin 13 is the ground for the clutch coil.
Pin 14 is the clutch positive lead.

By connecting pin 8 to pin 14, and then grounding pin 13, you bypass everything and engage the clutch... so, I would concur its not the controller that's causing your problem.

Looking over the diagnostic codes that the blinking light would generate tell me that there are codes for open circuits to the clutch coil, sensors, etc... but, none for a dead short. So, if the clutch coil or harness is shorted to ground, there wouldn't be a code generated.
So far, so good.

so, the question is... is the short in the wiring harness (hopefully) or the clutch internal to the transfer case?

The manual says measure the resistance between pin 13 and 14 with the control box disconnected. If its less than 1 ohm, you have a short.
If its between 1.5 and 4 ohms, its OK. This the resistance of the clutch coil itself.

Based on the fact that you keep blowing fuses, I can almost guarantee the it will be less than an ohm.
So, disconnect the plug on the transfer case that goes to the clutch coil and retest the circuit. If you still show a short with the harness disconnected at both the control end and the coil end, the harness is shorted somewhere.
If not, check the resistance of the coil right at the transfer case with the connector off... should be on the order of a few ohms. If its less than 1 ohm, I'm afraid you'll have to replace the coil.
Hope this helps. Let me know if you need anything else.
KenP

 

posting an e-mail I sent someone earlier:

I would try using the cruise control on a dry road and see
if that pops the fuse. Check the ABS too.

Then look for a short by disconnecting the negative battery
cable and attaching a test lamp. You should get a quick flicker
and that is it.

What I would do in either case, is remove the seat and remove the
control module. Then make sure the connector and the wires
have not been damaged by accident or rust from the floor.

I do not have my manual in front of me, but, if the module
fails the self-test it should flash nine (?) times.

(Though it sounds like a clutch problem with the transfer case).

Then trace the wires all the way back to the clutch. Make a few
test leads about 15 feet long with ATO fuses in each. I would go 3
amps on each fuse for testing the clutch wires. First test for
continuity on each wire.

Then go
(+)
(test lead)
(harness module end)
(harness clutch end)
(test lead)
(test lamp to ground)

You should be able to light up a small test lamp without blowing even a 1 amp fuse if the wires are okay.

Unfortunately, my transmission died a while ago so I have no way to
do a clutch or transmission test on the Aerostar for you because I can
not move it or jack it up where it is.

While you are under there, make sure the bolts for the
transmission/transfer case are nice and snug. Especially the ones at
the top of the case.

> This leads me to believe that the problem may not be a bad
> control module. I jacked up the front wheels and with the
> van in Park, I can turn one wheel but the opposite wheel
> and the front driveshaft do not turn. When I put it in Neutral

That is correct, because the front axle is connected to the rear axle
through the transfer case, which is connected to the transmission pawl which is what locks the axle.

The clutch ONLY engages at 5 mph or less. The transfer case always transmits a 1 to 3 split of torque to the front axle (unless defective). You should be able to put your vehicle up with the four wheels off the ground (lift by the lower control arms so there
is no droop on the front axle shafts), put it in gear and allow the motor, at idle, to spin the wheels on both axles. I usually keep my foot on the brake so it gets no higher than 5/10 mph on the speedo. Otherwise it will vibrate itself off the jackstands or lift.

You can leave the motor off, put into D, and turn the rear wheel which
should turn the front. Though I have never tested it like this before
myself. I usually used a lift.

 

Ken,

Thanks for the info. Based on the tests you suggested, I'm afraid it looks like bad news for me.

I did "Test F3: Continuity Testing of the Clutch Circuit" the other day and got a reading of 1.8 ohms between pins 13 & 14 which seemed fine. I just tried it again as you suggested and now it reads 0.00 ohms. I don't know why it was OK before but it's not now.

I also checked the resistance at the plug that comes out of the transfer case. It also read 0.00 ohms.

Sooooo, from what you're telling me, the problem is with the internal clutch coil. Any thoughts on removing it, splitting the case and replacing the clutch vs. R/R with a good transfer case from the bone yard?

Another member..."rebocardo"...just posted a few more suggestions to try which I will do and see if they shed any more light on the problem.


Thanks again,
Dennis

 

Dennis,
Yup, doesn't sound good. Once the system is unplugged from the contoller under the seat, its a straight shot to the electric clutch connector via pins 13 and 14. If you're getting a bad resistance reading at the clutch connector right on the the transfer case, I'm afraid your problem is in the case, not part of the cruise control or any other components. For other readers, the code light flashing 9 times (as mentioned in earlier posting) is not indicative of a bad controller... it is the DTC for mechanical slippage (i.e.) between the front and rear shaft outputs.
As you know, the clutch coil should read a couple of ohms, not infinity or 0 (dead short).
I just looked over the section in the manual concerning replacing the electronic clutch. Removing and splitting the transfer case doesn't look too bad... although you'll need a puller to remove the front drive shaft flange. The clutch is mounted with the planetary gear set on the stub for the front axle set inside of the case.
I'm pretty handy with a wrench, but not sure I'd dive into this given that Aerostar transfer cases are pretty plentiful and cheap. Just went to my favorite wrecking yard asset, www.car-part.com, and there are a number of them for $150 bucks or less. Once you put the car information in the search engine, it will give you yards/prices in order of price. Don't bother emailing the yards, most won't answer.. but a phone call and a credit card will get what you wanted shipped UPS to your door.
Sorry your new year isn't starting well, but at least you now know what the problem is and the fix is straightforward. A bit of wrenching while lying on your back, but not bad...
Happy New Year to all, KenP