rbeggs

I have always been able to hear the variorum in my '96c4s kick in. Lately, the sound and sensation is absent when getting up into that RPM range.

I have checked for actuator solenoid operation with the ignition on/off trick and the two that are visible appear to operate. What other conditions might cause the varioram function to be inoperative?

Thanks for any ideas.

-rb

il pirata

Search.

Here was the latest thread...

https://rennlist.com/forums/showthre...ferrerid=93689

mpruden

Good thread, as I've wondered the same thing. According to the WSM, you should just use a system tester to activate the varioram and watch the 3 actuators move. You can also do this with the key, as you mention.

You can see all three operate. An inspection mirror can help you see the lower one.

I'm not expert in this, but I have to think that if you can observe all 3 move correctly externally, then that proves many parts of the system are working correctly. Including:
1) You do not have a serious enough vacuum leak to keep the varioram components from moving correctly.
2) The computer can communicate with the varioram, so you don't have any electrical problems between the DME and the vacuum valve things (unsure the proper name for these)

I guess you could always have the "wheeler dealers" problem of something mechanical failing internally to the varioram, but I'm not sure any amount of chasing vacuum leaks or electrical problems would help you diagnose that kind of problem.

Garth S

As there is zilch engine vacuum when the VRAM is called upon to act ( foot well into throttle), start your search at the vacuum reservoir ..... the hard plastic line that connects to a rubber 'T' piece hidden on the left forward side behind the HVAC blower motor is either disconnected - or the interior of the 'T' has delaminated and the flaccid guts are acting as a check valve blocking access to the reservoir. There is a well posted 'stent' fix for the latter.

Open the link above and check out the well marked up diag posted by Bill V in post #3 - the 'T' in question is item #10.
I've noted that Porsche was a bit frugal with the vac lines, and the 'T' is often under some strain.

If an actuator had failed, there should still be some VRAM action - if you have nothing, the only way 3 actuators suddenly fail to function is loss of vac, not 3 blown diaphrams.

coreseller

I am technologically challenged in certain areas and this is indeed one of them. maybe it would behoove us in the 993 community to have group days where we could perform such tests as this to determine if our varioram {or whatever} is functioning correctly or not. I am in the SW Cincy area of Ohio and would gladly offer to host such an event with a grill and a cooler if anyone else {especially someone in the know} would like to attend. Obviously it would need to wait
several weeks for the weather. Let me know guys..............

mpruden

Let's assume that with the engine off, the actuators all move when the key is turned to the on position (powered by stored vacuum, I presume).

Is it possible that the actuators would later fail to move when the engine is running fast and vacuum is low? Wouldn't the same stored vacuum give the actuators enough power under high-rpm circumstances?

Holytin

Same happened to me years ago - inserted a spring into he collapsed T to keep vacuum going. There was an article about this topic somewhere but can't remember (RL, P-Car,...)

nine9six

If memory serves, a spring with a 5/16" OD x 7/16" length, with a spring coil OD of 1/32" will suffice. Home Depot.

To know for sure, do as I did...Pull the rubber T-fitting and measure for yourself. (recommended)

Garth S

Here's a post from '06 re the VRAM stent mod .... not to say that it is the resolution of the OP's issue, but it is a known recurrent prob. ...

rbeggs

This is all good information. I admit to a degree of laziness for not searching before asking. I impulsively cut to the chase. It happens occasionally in a weak moment. Apologies.

The post has stirred some interest and activity accompanied by a nice collection of useful links and thoughtful observations. That's a plus.

Now to find the time to act on this trove of information.

Many thanks,

-rb

schmidtwerk

I had an internal failure of the flapper box solenoid which caused total failure of the 3 VRAM solenoids all on the same vacuum line. This will only happen if the heat is selected on and the flapper box solenoid is energized. Unplug vacuum line to flapper solenoid and plug the line and retest. Additionally you can hook up a line direct to the solenoid, suck on it and see if it hold vacuum. Mine had a double failure. Recently on the dyno one intake tube VRAM solenoid wasn't working which when corrected increased hp from 285 to 308. Reinstalled in the car with flapper box found another bad solenoid. Think these are starting to fail with age. Remember, if car has sat, canister will loose vacuum. Try running at idle first to charge canister then shut off and retest solenoid operation.

Valego46

Hello there! I have the same issue...only with heater on the varioram is not working, can someone help to locate this flapper box solenoid Schmidt work is talking about!? Thanks for any suggestions