JF506E fault - anybody experienced this before?

[alienb4ndit]

Hi guys.

I've posted here recently asking for opinions on my 75. It had a non functioning reverse gear . I replaced reverse piston but only because I had the box stripped in order to remove reverse piston to examine it - could not find a crack anywhere. Built it back up and there was no difference (not surprising really). I've shelved the job for a month or two while I carry on with other projects and now I'm back on it and looking at electrical side of things.
I've got the valve body off and have been testing the solenoids. There are approximately 8 solenoids... 2 of which click nicely when 12v is applied to them. The other 6, however, do not click, they have shorted out. I've done a diagnostic check which confirms a short circuit.
My question is this...: Has anyone ever encountered such a problem? I am now in the process of checking the wiring to the gearbox ECU. If this checks out ok I may end up condemning the ECU... why else would "6" solenoids fail at the same time?
I don't want to replace the solenoids or box without checking what may have caused the problem as it may fry the new solenoids if the underlying problem is still there!

Any thoughts would be welcomed.

[DMGRS]

6 solenoids failing at once, especially to a short, is almost beyond the realms of probability. I'd definitely be looking elsewhere. :)

There's only 1 or 2 solenoids that are known for failing.

[mh007]

You should be seeing 9 solenoids by the way.

[SD1too]

Paul,

I agree with DMRGS I'm afraid. The results you have obtained from your solenoid tests should be ringing alarm bells. What about your earlier thread:

I've now checked resistance across all pins at the multiplug found at n/s turret. All readings were within spec ... all solenoids check out ok.
So what's changed?

Also, are you sure that you're following the MG Rover procedure for filling and checking the level of the ATF (I know from bitter experience on an AP transmission that low fluid affects reverse engagement), and are you using the correct N402 fluid? Was it one of these (http://www.the75andztclub.co.uk/forum/showpost.php?p=1138687&postcount=23)?

Simon

[alienb4ndit]

Paul,

I agree with DMRGS I'm afraid. The results you have obtained from your solenoid tests should be ringing alarm bells. What about your earlier thread:

So what's changed?

Also, are you sure that you're following the MG Rover procedure for filling and checking the level of the ATF (I know from bitter experience on an AP transmission that low fluid affects reverse engagement), and are you using the correct N402 fluid? Was it one of these (http://www.the75andztclub.co.uk/forum/showpost.php?p=1138687&postcount=23)?

Simon


I did a resistance check on each solenoid and all readings were good BUT the solenoids do not activate when given 12v. I am now checking the wiring to and from the gearbox /ECU. I'm hoping to find some damage.... if not I may have to replace the ECU as well in case its fried and damages a replacement gearbox!

[SD1too]

I did a resistance check on each solenoid and all readings were good BUT the solenoids do not activate when given 12v.
Paul; I seem to recall from MGR's technical manual that the solenoids are not triggered by 12v DC but by a pulsed waveform of some type. I will look it up tonight for you.

You haven't answered my questions about the fluid! Don't get hung up on the ECU. I bet you it won't be that. It's always easy to blame a mysterious box of electronics when you don't know what to do next. ;)

Simon

[alienb4ndit]

That makes sense! If the solenoids are PWM controlled then that would explain why I'm getting no response from them by just applying 12v.
I'm going to go and check the voltages to the plug for the valve body and see what I've got there.

In answer to your question about filling the gearbox wirh oil, No I didnt follow any correct procedure although I did put the correct amount in. I don't think lack of oil is the problem, even if the level isn't quite right.... it wouldn't cause me to lose reverse completely, overnight.
I'll report back with voltage findings and if you can see if there's any info on PWM signals that would help.

Thanks

[Anon3]

Interestingly, 6 of the solenoids are on/off and the other 3 are fed at 50hz cycles, according to the manual, which seems 100% wrong to what you're saying :shrug:

Relevant info attached and it's part 2 that explains :}

[alienb4ndit]

Thanks for that info, very useful.

Although some of the solenoids are duty cycled they are, at the end of the day, a solenoid. With that in mind surely they should click like any other solenoid?

It would be nice if someone had a valve block handy and could check it for me 😉

I'm at a bit of a loss right now as to what to do. Do I just bite the bullet and throw another box in it?

[Anon3]

Thanks for that info, very useful.

Although some of the solenoids are duty cycled they are, at the end of the day, a solenoid. With that in mind surely they should click like any other solenoid?

It would be nice if someone had a valve block handy and could check it for me 😉

I'm at a bit of a loss right now as to what to do. Do I just bite the bullet and throw another box in it?

I'd agree with that.
The 50hz pulses will be what makes them variable
And either way, they should not be showing short.

That said, I assume you mean short as in 0 ohms?
The correct figures are low.
And attached, just in case.

[Anon3]

Going back to your reverse problem.
Note that if the low clutch timing solenoid is turned on, the reverse clutch is drained and won't engage, inhibiting selection.
Could it be jammed in?
Possible, but extremely doubtful, especially for 6 solenoids.

Are you 100% sure you had enough oil in?

That still doesn't explain the solenoids being short though.

All 9 solenoids are available at just over £200 for the whole set; a road I'm looking at going down.
Expensive, but would clear them as an issue in my case;

http://www.onestopgearboxshop.com/collections/jf506e

[alienb4ndit]

I did a resistance test and all readings were correct which is why I'm struggling to understand why the solenoids dont switch when 12v is applied to 6 of them.

It may be that they are seized somehow and unable to move but electrically ok?

[Anon3]

Afaik, the usual problem is that they go open, although as you'll have read, they can go short to 5V or 12V.

If the resistances are ok, I'd expect the solenoids to be ok too.

Which is exactly where I'm at.
My resistances are fine, but the box is still clunky.
Which is why I'm only thinking about changing the lot of them.

And that's where I'm afraid I'm out of ideas.

[alienb4ndit]

So you have a situation where your solenoids aew reading good resistances but not working as they should?

Mine is that I have no reverse as well as very harsh gear changes and slipping.

Are the ECU's reliable enough... do they get water in the plugs or anything like that?

[Anon3]

I think Simon answered that one.
They're dry, so that won't be the problem.

Harshness, slipping and no reverse?
Blimey, you've got the lot there and a bunch of duff solenoids would explain that, but it just doesn't make sense that they'd all go together :shrug:

I'm more inclined to think there are more likely to be resistance type problems in the wiring because of age, myself.

[alienb4ndit]

Sorry, what did you mean when you said they're dry?

[Anon3]

The ECU is behind the glovebox and isn't known for getting wet.

[Anon3]

Ah, sorry.
Afaik, the ECUs are not known to be unreliable.
The multiplug connector is known to be iffy though, I believe.
There's a fix where people apply 2 jubilee clips round the plugs and cable tie the two together.

[SD1too]

Mine is that I have no reverse as well as very harsh gear changes and slipping.
Those are classic symptoms of low fluid level.
In answer to your question about filling the gearbox wirh oil, No I didnt follow any correct procedure although I did put the correct amount in.
How do you know what "the correct amount" is if you didn't follow MGR's method?

You haven't answered my question about which fluid you used.

Simon