Self Levelling Suspension

[kingscoop]

I had a leaking rear shock for a while and the self levelling pump had been running rather more than usual. Last week the pump stops working and after a 10-15 mile journey the warning light comes on.
I've just installed a new shock absorber and tried checking everything but it's still not working.
I took the compressor pump out and put 12v through it and that worked fine.
Between the pump and where the air lines split to go to each shock there is a 2" long cylinder with an electrical connection. Air line goes in and out of it and I can feel it clicking every 30 seconds or so. What is this bit?
I've checked the two fusees in the central fuse box. The ladder height control system is all connected.
Anyone help?

 

[hworksinc]

There are actually 4 fuses relevant to the Air-Suspension system - make sure they're all good:

Battery Junction Box (under the hood):
Fuse 9 - Powers the compressor
Fuse 8 - Powers the control module

Central Junction Box (in the dash):
Fuse 9 - Used for the Break pedal position switch (provides an input to the suspension control module among other things)
Fuse 10 - Powers the steering rate sensor and tells the control module when the ignition is in run

The black cylinder is (I think) the solenoid module that houses the fill and dump solenoids. Since they are clicking, it means that at least part of the control module is working fine.

It sounds like the system is calling for air, and triggering the solenoid, but the compressor is not actually turning on. I'd check the compressor relay - it's located in the Auxiliary Relay Box under the air cleaner. There are several relays in the box - the one for the compressor should be the large one on the end.

 

[kingscoop]

Thanks for replying.

Just checked the fuses and they are all fine. Looks like I have a different arrangement to your Explorer (UK version) and the fusebox is the same as post 6 in this thread http://www.explorerforum.com/forums/showthread.php?t=254896 There is no fuse 9!

I've electrically checked the compressor relay and that is fine. I can feel this relay clicking every 20 seconds or so in time with the solenoid (mine is off white plastic). I'm calling it a solenoid for lack of a better word. It looks like it could be stopping the air coming out of the shocks and opens when the compressor starts pumping.

I thought the dump valve was mounted next the the compressor and the 6" long black cylinder. If you look at post 3 in this thread http://www.explorerforum.com/forums/showthread.php?t=248754 it shows the compressor. My assembly has a 6" long, 3" diameter cylinder mounted next to the compressor and the post above it gives pinout details saying that two of the pins are for the dump valve. Could it be that I have an air heater mounted next to the compressor. I've read about the heater as well but not found out where it is. Apparently the compressor will only work when the heater is up to temperature.

I will admit to taking out the car radio last week and installing a new radio. Somewhere I have read that the self levelling control module is located behind the radio. I have a module either side of the radio opening, anyone know which one is the self levelling module so I can take a very careful look at that one - space is very limited in there.

 

[hworksinc]

Yes - ignore the Fuse 9 for the BPP switch - apparently that does not exist on RH drive!

The control module is indeed next to/behind the radio. In the US version, it's on the right side, but I don't know about yours. The other module in there is the GEM (has 4 big plugs on it). The suspension control module should have 2 plugs going to it, one black and one grey.

Sorry - I mistyped in my original post. The solenoids I was referring to are the fill and gate solenoids. The vent/dump solenoid is larger and is mounted to the compressor assembly as you found. The fill solenoid allows air flow to the air shocks and is between the compressor assembly and the gate solenoid. The gate solenoid (downstream of the fill solenoid) isolates the two air shocks from each other when the system detects uneven lateral loads (eg when turning). Which one of these is clicking?

None of my schematics mention a heater associated with the air suspension system. There is a passive air drier in the line, but that's all I've found.

If that compressor relay is clicking but the compressor is not coming on, it sounds like the control system is working since it's calling for the compressor to turn on. I'd recommend using a multimeter and checking for voltage at the relay contacts (verify that 12V is being supplied to the relay contact from fuse 9 under the hood). The relay panel is very susceptible to corrosion. Power should be coming in on pin 87 of the relay connector (closest to the relay box mounting tabs). If there IS voltage there, it wouldn't hurt to swap the relay (even though it tested ok). If that doesn't do it, check to see if you're actually getting 12V at the connector for the compressor. Corrosion is a concern at any of the junctions on the way to the compressor. You might also need to check the ground wire at the compressor connector.

 

[BIGHVM]

Have you checked the ladder is connected, sometimes the balljoints can come loose, get under her and with the ignition on, look at the top and bottom of the ladder, if they are conected, puch the ladder up and see if that triggers the compressor- it should and you should see the rear going up. Let us know the result mate!

 

[kingscoop]

Thanks both of you.

The ladder mechanism is fully attached, I tried disconnecting one end and pushing up to compress the trigger and no action from the compressor. I also tried pulling it down as well - no joy.

I'll check the power supply to the relay in the morning. Something I didn't think about! I'll also try swapping relays - I believe there is a similar relay in the main fuse box. I can also try bypassing all the wire from the relay to the compressor and see if I can get it to fire up.

Control module to the right - I can't actually reach the wire connectors and will have to dismantle the dash to get in there. Last resort since it does sound like it is functioning.

Air drier - air heater. Sure I read that it had to get up to temperature but who knows where that bit is?

I'd had a good look underneath and hadn't noticed these two gate solenoids. I have the compressor and fill solenoid and the big black cylinder with one air tube coming out of it. The air line goes into my off white plastic "solenoid" and has one pipe coming out of it. There is also an electrical connection to that "solenoid" with two wires and it is this that clicks. After the air line comes out of the "solenoid" it goes to a t-piece and then an air line goes to each shock. All this gubbins is mounted on top of the chassis and felling it all by hand I really didn't notice anything else in the line.

 

[kingscoop]

Thanks to your help I feel that I might be getting somewhere. There is no power to pin 87 on the relay but I do have power on the fuses.
Can I assume that there is (or should be) a direct connection between the fuse and relay so that I can "hotwire" the relay and see if that gets the compressor running? I've let more than enough smoke out of electrical components in the past to be a bit wary of destroying my pride and joy!

 

[hworksinc]

Yes - fuse 9 connects directly to the relay.

 

[kingscoop]

Hworksinc, you are the greatest, where did you get this wiring diagram from?

I have the Haynes and Chilton manuals and their wiring diagrams leave something to be desired. They have no mention of the suspension control system. I remember the old Haynes wiring diagrams where the whole circuit for the car was on one page and you spent ages trying to trace wires but this partial schematic is so easy to follow.

The auxiliary fuse box is almost what I have, there is a small relay where the high speed blower relay is. The washer relays are the same because I had trouble with those before. A quick wriggle and a spray with WD40 sorted them out.

Can't get to have a play about for a couple of days but will let you know how I get on.

By the way, did I tell you that you're the greatest?

 

[hworksinc]

These are from the factory service manual (3 volumes - 2 books focused on troubleshooting/repair/replacement and 1 book of wiring diagrams). I bought mine on eBay a few years ago - absolutely invaluable. My books are for the 2000 model year, but most things are the same for 99. I don't know about the availability of the manuals for the UK version - can't say I've seen them but then again I've never really looked.

I might have a CD version of the 1999 manual - if that would be helpful let me know. If can dig it up I can put it online and send you a link to download it. It has the same information that the books have, though the interface is a bit cumbersome.

 

[kingscoop]

Victory is mine.
There was no power on pin 87 so I took the air filter out and eased the auxiliary fuse box off of its bracket and took the bottom off. There was a load of crap in the bottom and the terminals to the relay were very corroded. Pin 87 was disconnected. What seems to be happening is that the bottom of the relay box where the wires enter is exposed to the elements and water is getting in and collecting.
I've rewired the relay and it all worked straight away. What a relief.
A link to the 1999 manual would be fantastic if you could do that for me. I'll start looking for a UK manual on Ebay but don't hold out much help. I certainly need something better than the two manuals that I have.
Thanks again.