oz928s4

Thanx jon

the flyin' scotsman

You posted that the 'clicking relay' was XVIII which is the flap control relay...............did you change it and what was the effect? If the relay is no longer clicking but the flaps are always moving then we need to look at the input signals.

The tech book notes 4 inputs:

rad coolant temp
ATF temp
Intake air temp
Refrig. pressure a/c

oz928s4

I have to get my A/C topped up today i wonder if that might be the problem

the flyin' scotsman

Doubt it; haven't had a good a/c system for years and the flaps worked ok until I dumped them.

Can you cycle the flaps through their complete range manually?

oz928s4

Not sure what you mean by cycle manually.
When i plug the loom back together they cycle thru the entire range of open ...close and just keep going open...close......

Alan

As I noted earlier - I'd suspect the motor position track as the culprit. You can test the controller a little to see if it works- But I'd suspect it works OK - they seem to be very reliable from the lack of reported issues (of course many deleted the flaps at some point - functionally at least).

On the car side of the connector not sure if you can see the pin ID's If you can - the way it works is that Pins 5 & 6 are the motor 6 is ground and 5 is from the flap relay. Pin 4 is the switched ground for the flap relay - when its grounded the relay runs... yours must be grounded all the time somehow.

Pin 1 and 2 are the feeds for the Open & Close commands from the fan controller. Not sure which is which for sure but I'd assume Pin 2 grounded = Open Fully and Pin 1 grounded = Close Fully (may possibly be swapped). Pin 3 feeds back to the fan controller and seems to be an intermediate position option via the controller (perhaps).

So you can test those output levels from the controller depending on the mode .. or you can test the switch connections as the motor rotates - connect 5/6 on the motor side to power/ground to get it rotating and see if you see connectivity drop between 4 & 1 in the fully closed position and connectivity between 4 & 2 drop in the fully open position.

This should tell you if its the motor or the fan controller...

Alan

the flyin' scotsman

The flap motor has a thumb wheel where you can move the flaps from one extreme to the other, its below the rubber (condom) cover.

Once confirmed I'd disconnect each input in turn; the easiest is the intake air temp switch.

pmb692

Just found I have a continuous flap operation problem on an 88 as well.

dr bob

Flaps are driven by a control module that lives under the cover next to the passenger's seat. It looks at coolan temp, refrigerant temp, and transmission oil temp to determine wheterhr the flaps need to be adjusted. The logic is very similar to the logic that controls cooling fan speed, also managed by that same controller. If your cooling fans are working correctly, you can probably rule out sensor problems and focus on the flaps directly.

First and most important thing is to clean all the connections including the grounds. That almost always solves erratic operation issues. The flap actuater receives position commands, and needs the swicth feedback to be correct when the flaps reach the target position. Just a little corrosion will cause the continuous operation as the flaps hunt for a position they can not see.

ROG100

The flaps were a good idea but in practice proved very troublesome and in worst cases causing severe overheating of the engine. Porsche removed them in subsequent years.
Make sure the flaps are in the open position and pull the fuse #23 and peace will be restored to your 928 World.

dr bob

FWIW, living in the, um, cooler climates now, I'm thinking hard about putting that fuse back in. Should help get the engine and the cabin both a little warmer a little quicker in the morning.