Calling anyone who understands the hydractive electrovalves

Unread post by **Dommo** » 18 Jan 2010, 11:58

Hi folks

I've bought an Activa and it had a leaky electrovalve, a spare XM hydractive electrovalve was supplied with the car to replace it. Upon inspection I found it was the Activa anti roll electrovalve that was leaking and not the hydractive one.

I've stripped both electrovalves and the only difference I can see is that the flat spots on the sprung pin that the slug sits over are different by a few mm, and the length of the coil is 0.7mm different, as is the alloy part. So when I rebuild it using the hydractive alloy part and activa everything else there is a bit of slop - ie, the crinkle washer is still slightly crinkled, is that normal??

And secondly, we rigged up a 10v supply to the coil (just to see if it did anything) and it did, but it wasn't particularly powerful. And we also put the 10v supply to the coil when we rebuilt the electrovalve assembly, and there was no noise from the internals. We assumed there'd be something from 10v, although not a lot, but there was nothing.

We're struggling to understand how the electrovalve works, are both the input and output (not the leak off) on the sphere body side of the valve - the alloy part? Surely the coil we attached to a 10v supply isn't powerful enough to counteract the massive pressure of the hydraulic system?

I assume we're missing something obvious but we need someone to tell us!

Thanks a lot. Dom.

Unread post by **CitroJim** » 18 Jan 2010, 13:00

Dom,

Firstly NEVER apply a DC voltage to the electrovalve. They're designed to run on a 1KHz PWM signal. 10V DC (if applied for more than a few seconds) may destroy them and if wrong polarity will damage the back-emf diode.

That's not the way to test them

You'll hear nothing much from them just applying a vlotage.

Their off (hard) condition is achieved by the pressure of the bigger spring holding the needle valve on the seat in the alloy body.

When operated, the coil generates a magnetic field that moves the slug upward against the spring and lifts the lower needle from the seat. Lift ing the needle from the seat opens a passage between the middle and periphery of the threaded part, essentially between the two green O rings.

The spring tension is such that the valve only operates with BOTH an electrical signal AND hydraulic pressure present.

The top pipe connection is the leakoff outlet. Leakoff is only egffective when the valve is between states. In going to the operated condition the leakoff valve is closed by the upper part of the needle valve. You find in practice that there is a "spurt" of leakoff when the valve switches.

I hope you have not ruined the good valve you have by trying to test it.

Unread post by **Dommo** » 18 Jan 2010, 16:12

Cack. How would I know if I've knackered it? And how about the diode? Cheers.

AndersDK · Unread post by **AndersDK** » 18 Jan 2010, 16:18

The valve is a coil with low ohmic resistance.
If cooked they are disrupted = high ohmic.

The diode is connected in parallel to the low ohmic coil, and can not be checked by any normal means.

Unread post by **CitroJim** » 18 Jan 2010, 20:12

The only real way Dom, to test an electrovalve, is in-service.

If it hums and clicks as it changes state then it is working, as confirmed by a noticeable hardening and softening of the suspension. The Activa electrovalve is harder to test but a drive will soon show it working or not. If it goes round corners on rails with no roll, it'll be good.

Have a look at the Activa Buyers Guide as that tells you how to check.

An additional check is to slip off the leakage return pipe, slip on a length of pipe into a jamjar and check there is minimal leakage in both states with a "spurt" as it changes state.