UKSaabs

So your having boost problems and suspect your APC valve could be defective. Here's a few things to try...

First use a solvent cleaner/carb cleaner and blast it down all 3 ports and keep an eye out for any debris or discoloration in the fluid coming out. Keep blasting through till the fluid that comes out is the same as what's going in. This is cleaner I use.


If this doesn't solve the issue and you have access to a DVM/Multimeter you can check the continuinty between the coils inside the APC. To do this set your DVM to Ohms and rest a probe on the centre pin and then place the other probe to each of the end pins on the APC (photo of pins below)


You should see a value of 3 ohms. Most working ones I've seen are usually within a .2 tolerance so I'd say 2.8 to 3.2 ohms is good. The two outer pins should be the culmination of your 2 values (around 6 ohms). If this checks out ok your coils are working and intact. If you find one or both coils open circuit all is not lost.

If you suspect the valve to be sticky or the pin resistance is zero or out of spec you may wish to dismantle the APC which you can do with a couple of craft knives. The best place to start is under the pin housing as this is where the most glue is.

If you can get a small hammer tap the knife into the seam (like in the photo above) and work your way around the circumference of the valve. It will take a bit of time but it will come apart. Once the bottom has come off you can clean the valve better and use a bit of compressed air to blast up the centre hole and down the nozzles.

If your valve resistance values were reading zero (open circuit) check the thin wires that go to the pin chamber haven't snapped or come lose. If they have just solder them back on as its easy enough to see where come from. If the wires look ok check resistance directly from the soldered pins. If they still read zero im afraid it's the end of the road as the breakage has occured on the coil winding itself. After thoroughly cleaning the valve and blasting air though use a very thin oil and drop or spray a little up the centre hole at the bottom of the valve and give it a good shake. If you can hear a little metallic clicking or rattle and the little plug feels like it's now free its time to glue it back up like this.

The glue and oil I use a pictured below.




After gluing I leave the valve to go off, clamped hard in the vice.

Hope this helps and good luck.

Good post Phil, moved to the knowledge base.

There is also meant to be a method of checking which involves energizing the centre pin with 9v and briefly touching each outer pin and it should move the floating valve to each respective position. I've never tried it tbh so can't vouch for it.

Nice write up, thanks.

What do you use the silicon spay for?

To add to the electrical test, it is possible to do a basic flow test on the valve. It's function is to act to divert pressure away from the wastegate. It does this by varying the ratio of connection of the wastegate to either the compressor or return flow. All compressor, you get base boost. All return, and max boost. The 3 ports are labelled (top to bottom)

C ompressor
W astegate
R eturn

If you try blowing through the ports, you should only ever be able to blow from C-W or R-W, and only one of these at a time. Test it by covering W and trying to blow through C or W. You should have no flow on a good valve

By dabbing a 9V battery alternately between the middle contact and the outer, you can force the valve to switch. You should hear a click and the flow of air will switch from C-W to R-W or vice versa.

Mark E wrote:To add to the electrical test, it is possible to do a basic flow test on the valve. It's function is to act to divert pressure away from the wastegate. It does this by varying the ratio of connection of the wastegate to either the compressor or return flow. All compressor, you get base boost. All return, and max boost. The 3 ports are labelled (top to bottom)

C ompressor
W astegate
R eturn

If you try blowing through the ports, you should only ever be able to blow from C-W or R-W, and only one of these at a time. Test it by covering W and trying to blow through C or W. You should have no flow on a good valve

By dabbing a 9V battery alternately between the middle contact and the outer, you can force the valve to switch. You should hear a click and the flow of air will switch from C-W to R-W or vice versa.

Thanks For the added info Mark.

@Kev

I use the silicon oil to very lightly lubricate the chamber in which the floating valve travels. Just a tiny spray or drop of a very thin oil down the bottom hole when it's apart really helps after cleaning.

Inside the metal block (two facing electromagnets) it's bult like this



The ###'s are the metal body / electromagnets
The ________ is a metal ferrous disc which gets pulsed up or down to seal the hole on the middle of one of the elctromagnets

You can just see the disc/valve in this picture. It only travels around 2 or 3mm in the chamber but can become stuck. With a good clean and lube it can be freed up.

like above

a bit further...

Brilliant write up Phil, so wish i'd had your knowledge. As when i had the 9-3 i went though four of them in a year . the carb cleaner made them work for a little while , but all but the final one packed in.

Now its in an Astra Coupe.