Anyone Here Ever Successfully Repaird a Bad DME w/ a Weak Solder?

[Jehu]

The other night the engine began stumbling and hesitating terribly.

At one point I stopped and swapped in another DME and the engine ran normally .

The next day I refitted the DME I removed and the engine again also ran normally.

The running was so bad I could only manage to keep it going in fourth gear on highway and third on town streets.

I am pretty sure the electronic case cooling fan has not been working and I suspect a solder has become weakened and loosed after several hours of long distance driving and after sitting a night in the cold car it settled back down..

I have looked for replacements.. its a 1995 EWSII unit so not falling off trees.

I want to try looking for the problem on the boards in the unit and attempting to repair it if I find such an issue.

going to get one of these 8388

Anyone had any luck doing this?

[shogun]

I only know of this DME resoldering info and pics, that is the older 0 261 200 059 The car: '88 BMW 535is http://www.e38.org/e28/louielouie/dme_fix.html
but should be a good guide.

[Jehu]

I only know of this DME resoldering info and pics, that is the older 0 261 200 059 The car: '88 BMW 535is http://www.e38.org/e28/louielouie/dme_fix.html
but should be a good guide.

Ok thanks, I'll update after I open and see if I find something clearly broken..

[genphreak]

On an early M50 Motronic 3.31 (similar to M60) one of my spark output transistors failed.

Despite what you think the ebox fan may be fine, you can unplug it to test if it is or not. The later ones seem to last forever.

It wasn't hard to replace, but finding the replacement was, try www.digikey.com or one of the online transistor specialists

[Jehu]

How did you go about determining the fault was a transistor? can that cause an intermittent issue as in my case where after a day sitting the issue wasn't present?

Just interested what I might need other than the magnification to spot any issues..

Did you need to have some way to apply current to the various pins while it was open and test with a multi meter for faults?



On an early M50 Motronic 3.31 (similar to M60) one of my spark output transistors failed.

Despite what you think the ebox fan may be fine, you can unplug it to test if it is or not. The later ones seem to last forever.

It wasn't hard to replace, but finding the replacement was, try www.digikey.com (http://www.digikey.com) or one of the online transistor specialists

[genphreak]

Well it was very easy in my case: One was burnt and cracked, so no need to test it. If there are thermistors, diodes or resistors nearby replace them too for good measure- the local heat/circuit currents may have damaged them.

To test the transistor pins with a multimeter/trans tester you have to remove it AFAIK. Not hard as these are large ones- it is quick to remove them all. Also, if one or two are faulty, removing and replacing the others will ensure the joints are all re-flowed- ***which I forgot to say before- is the first thing to do, if you have not done it already- i.e. Remove, re-flow, replace, test- this may cause it to work with no further effort!

[Jehu]

Right on M8.. glad I have a spare EWS bypassed DME to keep me rolling in the meantime..


Well it was very easy in my case: One was burnt and cracked, so no need to test it. If there are thermistors, diodes or resistors nearby replace them too for good measure- the local heat/circuit currents may have damaged them.

To test the transistor pins with a multimeter/trans tester you have to remove it AFAIK. Not hard as these are large ones- it is quick to remove them all. Also, if one or two are faulty, removing and replacing the others will ensure the joints are all re-flowed- ***which I forgot to say before- is the first thing to do, if you have not done it already- i.e. Remove, re-flow, replace, test- this may cause it to work with no further effort!

[632 Regal]

How did you go about determining the fault was a transistor? can that cause an intermittent issue as in my case where after a day sitting the issue wasn't present?


This sounds more like a capacitor.

[Jehu]

This sounds more like a capacitor.


Interestingly enough I put the DME in question back in and it was OK.. I have had it in since the day after this happened and its been fine every day..

I am flumoxed... possibly it was a very slight weakness and the extreme cold we've had right along is keeping things tight or...

or I don't know.. maybe I guess it could have just been coincidental and the problem was a ton of water in the fuel and it just happened to work itself through at the exact same moment I changed DME's....but that seems extremely unlikely.

Bottom line I have the back up stock unit in the trunk if I find this happening again but next job is the AC evap/expansion valve.

If anyone wants to chime in this is the DIY guide I will be referencing ;

1995 525i EVAPORATOR REPLACEMENT

Ok, I got this one.

I did the dye thing with the glasses and UV light and did not see anything under the hood or the front of the car. I purchased a sniffer thing at Harbor Freight tools and could not detect anything. I did the dye thing again and noticed that the dye leaked out the bottom of the car after several hours. The dye was coming out of the evaporator spill tube (where your water puddle comes from).

I read several postings and could not get a clear understanding on what I needed to do. I ended up finding and pulling out the evaporator with a little bit of a challenge after several hours worth of effort.

First of all, you can get the evaporator out without having to remove the dash like I read somewhere. Here are the steps I took
1. Remove glove box
- release the clips on the rear of the box where the glove box pivots on the metal rod. Need a little force to release
- release strap from the door by removing the clip
- release shock absorber looking thing on the left side
Wiggle box off the metal rod, the whole box will pull away
2. Remove carpet panel on right side of center console by removing Philips screw
3. Remove plastic floor vent behind glove box by removing the 2 screws by the pivot bar
4. Remove plastic cover on the right side of the center console. This is the piece where the flashlight plugs in. There are a couple of screws and some clips. You can let this piece hang without having to remove the electric connection
5. Remove evaporator side panel. It has 7 T20 torx screws (the top 2 screws are longer but he other 5 are the same size). After you remove this piece, you will be able to see the evaporator and the expansion valve. Too bad you can't just (easily) grab and pull this out because you have to disconnect the high/low gas tubes. There are 3 thick bundles of wires that will get in the way of sliding out the evaporator. These bundles are plugged into a control module tucked behind the center console and the firewall. The control module easily slips out by depressing the tab and pull it out. You can leave this hanging, no need to disconnect the plugs

Here comes the fun part...If you look at where the expansion valve connects to the tubes through the firewall, you will notice that those pieces are held together by a bolt coming from the direction of the engine compartment (why make it easy from the passenger compartment side). Go to the engine compartment and see where the high/low tubes goes through the firewall. I pulled back the rubber gasket/grommet thinking that I would see the bolt I needed to remove but I was wrong. Instead, those tubes do a 90-degree bend toward the center of the car and then does another 90 degree bend towards the passenger compartment about 3 inches after the 1st bend. Check out www.realoem.com (http://www.realoem.com) to see diagram of that part). How do you find the bolt? Ah, here is the trick, there is a black plastic cover over the firewall, who knows the purpose of this. You do not have to remove the whole thing, only remove the screws on the side closest to the tubes.

Go to the engine compartment:

7. Remove 2 - 7mm hex head bolts that hold the plastic cover to the firewall. Pull back on plastic cover and you can see where the tubes make the final 90-degree turn through the firewall. I jammed in a screw driver to hold the cover back.
8. Get long extension and use 12mm socket to unscrew bolt between the tubes. I used a u-joint on this. You might have to use a deep socket.
9. Remove 2 T20 torx screws to the right, these hold the bracket to the firewall on the passenger side. I had to use a socket torx on an extension. I don't think I needed the u-joint on this. This will be the tough ones to get back on when this is reassembled.
10. Not entirely sure if this step is required but I disconnected the double pipe tubes near the fill valves so I could pull the tubes away from where the tubes connect to the evaporator valve.

At this point, the evaporator can/should slide out. The fins might get caught on plastic housing so it will take some wiggling a bit to get it out. But, you won't be able to get it fully out of the housing because the expansion valve will hit part of the dash so the evaporator valve needs to be removed.

11. Using 5 mm Allen wrench, remove the screw that holds the expansion valve to the evaporator.

You are done!!! If you did the dye test, you will see some of the dye inside of the housing. The big question is if your leak is from the evaporator or the seals between the expansion valve and the evaporator. Look what looks wet from the dye/oil. My seals were nice and dry but the fins had the green dye.

While you have everything apart, you might as well replace the air filter that sits in front of the evaporator. If you are like me, this filter has never been replaced and was thick with black dust/dirt. To get that out, you need a T20 torx to remove a small screw at the bottom of the white door. The top has a latch you have to switch counter-clockwise and the door pulls off. Grab the filter and pull it out.

Hope this helps. One of the postings said this is a $3,000 job at the dealer. I found the evaporator for $150 on ebay. Some were as high as $250, dealer price is nearly $600. I have read several suggestions that the dryer needs to be replaced (under the windshield wiper fluid bottle). I have seen this for about $50. They also suggested that all seals be replaced (about $15). The also said I might as well change the expansion valve but that can be expensive. Need to vacuum air/moisture out. If you don't have the equipment, an A/C shop can do this for you.


I inadvertently added Compressor Oil (forgot my reading glasses) and the system got jammed up and there was also I hole in one of the pipes along the front fender..

I replaced the Receiver/Dryer and it worked ok for a few weeks then I went over a railroad track too fats and with just the blower on suddenly smelled something ghastly.

I have since been smelling what I think is compressor oil or refrigerant volatilizing when I have the heat and have been seeing a smallish clear oily stain under the area where the airbox is located so I am thinking the evap blew and that half a can of compressor oil is all over the inside of my airbox...

[632 Regal]

I have an old vacuume pump I use when evacuating. It says it goes negative pressure but thats impossible so I let it run over night and then close everything off and add new oil and refridgerant. Make sure to drain as much oil as you can cause if you don't it can lock the pump. I think this was mentioned if your post. Other than that watch the bubblizer when charging until the bubbles just go away. Any more and you will have problems.

[Jehu]

I have an old vacuume pump I use when evacuating. It says it goes negative pressure but thats impossible so I let it run over night and then close everything off and add new oil and refridgerant. Make sure to drain as much oil as you can cause if you don't it can lock the pump. I think this was mentioned if your post. Other than that watch the bubblizer when charging until the bubbles just go away. Any more and you will have problems.

I am going to be doing it at a shop but not sure they have a vacuum system.. last time he filled it he just had the gauges and a tank.

If he has no vacuum I guess I'll take it to a shop with a Snap-On machine and properly evacuate it and test for leaks before filling it.

Now I read if the system is open for any length of time over a few minutes the Dryer will require replacing.. should I have one on hand if I run into delays putting the pipes back on the new unit?

I just replaced it a few months ago but if there has been a leak of any size is that enough to contaminate the dryer ( with moisture I assume) and result in damage to the compressor if that isn't already the case?

[632 Regal]

If you have a leak and no pressure left then I would replace the drier again. If it still has pressure it probably is not contaminated yet.