Imo000

Anyone knows what the voltage is for the Variocam actuator? I'm getting ~3.3V after 2000rpm. The other pin has a constant battery + (~13.8V) when the engine is running. This is for a '99 C2 (3.4).

Ahsai

The pin that has 3.3v is the "ground" supplied by the DME. When I don't know the exact voltage when variocam is triggered, 3.3v sounds low enough as the solenoid will see 13.8v-3.3v=10.5v across it, which is plenty to actuate it. What problems are you trying to solve?

Imo000

I have a P1539 code that points to a possible solenoid issue on the passanger bank. I'm trying to check every other possible causes to make sure its not something else like the wiring. How can a "ground" be +3.3V?

Ahsai

The DME uses transistors (not relays) to supply ground which will not be able to pull the voltage all the way to ground. Also, I'm not sure if the DME uses pulses (PWM) to modulate the voltage to the solenoid. I know it does for the timing solenoid in variocam+. For variocam, I think it's a simple on/off. If it does use pulses though, the 3.3v you measured would be an average value of the pulses with some on/off cycle. However, I don't think that's the case.

Anyway, what matters is the voltage seen by the actuator. You can measure the voltage between the two pins and it should be ~10.5v based on your previous measurements. You can unplug the solenoid and supply 12v to it when engine is running. Idle should change. Have you tested the other bank? Same voltages?

Ahsai

Fyi https://rennlist.com/forums/996-foru...el-1539-a.html

Imo000

I had access to a Durametric cable so had the solenoids turned on and off on both banks. The driver side (bank 1).reacted the way it should and the idle sutbked but nothing happend for the passanger side (banks 2). I will measure the voltage between the pins and set something up to ppwer the solenoid remotly to make sure its not working. I'm pretty sure at this point the solenoid is gone but want to be 100% before moving on to pull the valve cover.

Ahsai

Sounds like a good plan. You may also want to ohm out the resistance of the solenoid ~13 Ohm, as mentioned by Logray in post #3 in the link above. If you want to make sure there's enough power reaching the actuator, you can hook up a 12v 6w light bulb (e.g., our peanut size front parking light bulb) in place of the actuator. When rev over 2k or actuated by Durametric, the light bulb should light up. That will tell you the DME is providing enough current and the wiring is good all the way to the solenoid.

If the resistance checks out and you can hear a click on the solenoid when powered, maybe the solenoid itself is OK but the actuator is stuck at the idle position. Either case, it needs to be torn down and replacement of both the solenoid and actuator make more sense due to labor.

Let us know what you find.

Imo000

Got tons of those bulbs laying around. Will try that in a couple hours. Getting to the connector was a real PITA, the AC hose and the big coolant hose are in the way. Had to do some creative prying to get the harnes side disconnected. The solenoid side will be a pain to get acess too. I'll try to pull it from below. As usual, I'll report back with everything I find. That's the only way this and other info will ever be usefull in the future.

Imo000

Some update. Hooked up a 3W peanut bulb to the harness side and it didn't light up. Then I disconnected the bulb and re measured the voltages on the two pins and the B+ was still normal (13.xV) but the other one (I call it trigger pin) now went down from the previous +3.3V to +1.9V. Then checked the trigger pin to see if it was grounding to the chassis and it wasn't. After his I checked for resistance and above 2000rpm the trigger pin goes to ~1600 ohms. This is the same time as when the solenoid is supposed to be triggered. There is something weird going on with the trigger pin (haven't yet checked the solenoid yet). I have also tried turning the peanut bulb on with the trigger wires +1.9V and the bulb did not turn on however at the same time the voltage dropped to pretty much zero (+0.07V) AND the resistance showed an open circuit. I'm starting to think the trigger wire is broken somewhere. In the next few days I'll get the info for the pins at the DME and pinout the harness between the solenoid and the DME.

Ahsai

Imo, slow down a bit First, do NOT measure resistance on the trigger pin unless it's disconnected from the DME! It's connected to the DME directly so you risk damaging the DME by doing resistance measurements, where power is sent from the multimeter to the object being tested.

I do not think your trigger wire is broken or shorted. You would have seen no voltage if it was. You are sure the light bulb is not burned? Can you just measure the voltage between the two pins on the harness side? i.e., red probe on one pin and black probe on the other pin (not using the chassis as the ground). If you get 10v or so when the solenoid is supposed to be triggered, the light bulb should turn ON.

Imo000

I checked that too. Voltage between the two pins is the same as the B+ (~13.4V) all the time, regardless of RPM. The bulb is good, I checked it with the B+ pin and the chassis ground and it lit up nice and bright but when I replaced the chassis ground of the bulb, with the trigger pin, it didn't light up, even above 2000rpm. I will stop the resistance tests.

Ahsai

Um...interesting. I agree that does sound like something funcky going on with the trigger wire. So when the bulb is connected, somehow it doesn't provide a low voltage.

I guess next step is to ohm out the solenoid and hotwire 12v to it and see if it works. If it does, that means the problem is only on the DME harness side.

Btw, DME 5.2 pin 25 is the trigger wire for bank 2, and pin 52 is for bank 1. Easy to remember with the digits reverse of each other.

Imo000

Thanks for the info, I'll dig into it tonight.

Imo000

To hotwire the solenoid, one pin needs to get +12V and the other -12V/ground? I'm planning to use the jumping post in the engine bay for the +12V and the chassis as the ground.

Ahsai

That should work. One pin to +12v and the other to any ground point or chassis. There's a brass color bolt on the airfilter box close to the latch that provides an excellent ground.

Just be careful that the +12v jump terminal in the engine bay is ALWAYS hot, directly connected to the battery +ve terminal and not fused.