jschiller

While poking around the CE panel, trying to locate the source of a recent battery drain issue, I discovered a PO has pulled fuse #23 out of the panel. My chart says this is the Cooling Air Flap Adjustment fuse but the wiring diagram calls it the Fresh Air and Flap Control. So I'm not sure of its function. I resisted the temptation to putting a new fuse in there to see what happens (mostly because I didn't have the proper 7.5 amp fuse anyway).

But I wonder why the fuse was pulled. Is this a common way to disable the grill flaps so they remain open or could there be more to it? Is it A/C related? What is the proper way to troubleshoot this? There has to be a better way that just sticking in a new fuse and seeing if it blows or starts letting the smoke out of the wires. Does anyone know what resistance I should see on each leg of the fuse holder with power off and the fuse out?

Kevin in Atlanta

When the flaps misbehave by closing and staying closed your car will overheat so it became standard practice to manually open them the full open position and pull the fuse. 90 and up 928s no longer had the flaps.

jschiller

Ah, since the flaps are currently open and I'm not experiencing any overheating issues, I will leave well enough alone and not replace the fuse. But it's going to bug me that there is something broken. Maybe when everything else is fixed, I'll take a look at it.
Thanks, Kevin.

polecat702

The 2nd stage controller, is that finned box at the front of the passenger side under the hood. I think Greg Brown rebuilds them and whatever he does makes them bullet proof. Send him yours, it'll be guaranteed never to fail.

dr bob

The flaps concept started as a way to lower the Cd on the S4+ cars. Whwn cooling demand was lower with lots of airflow available at speed, the flaps would go to a mid position so the nose looked smoother. On a cold engine, the flaps stay completely closed to speed engine warm-up. On my car I noticed that the car would warm up with flaps closed and fans off. When the engine gets to temperature, the flaps go to mid position and the fans start at mid speed. There's no flaps-at-mid-position and fans not running state in the middle, so the fans end up running from the time the engine makes normal temp regardless of available airflow from car movement. In the month that didn't demand AC in SoCal, this seemed like a conundrum that could be easily solved by pulling the fuse. Now that we are in the 4-seasons climate in Oregon, the fuse is back in and the flaps do their duty as designed. The heater starts warming the cabin before I reach my destination so all is working as designed.

With your location in Florida where engine and cabin warm-up is very seldom delayed even on your most frigid [brrrrr!] mornings, leaving the fuse out and the flaps open is undoubtedly the best option. Not that many opportunities to stretch the legs out to north of a buck-fifty, where the flaps-closed drag reduction would be noticeable.

jschiller

The whole flaps/fuse issue might also be related to my DS fan not kicking on when the temp comes up. It just might be that a rebuild will solve that as well.

polecat702

I'm on my 2nd controller, for the 2nd stage, and like a dummy, I tossed the other one out, just before Greg posted that he was able to rebuild them. My fuse is pulled cause the one in the car doesn't open the flaps. but both of my fans will run when the car heats up to temp, or when the AC is on as they should. When I do the intake refresh, and replace the head gaskets, I have to give Greg the heads off my 89, I'll have him do the 2nd stage as well. Both fans should run even with the fuse pulled. The controller opens the flaps, and controls the fan speed, if I'm not mistaken.

worf928

Mrmerlin

NOTE a non running fan is usually a bad fuse connection from corrosion or the fingers have gotten spread or the fuse blade is thin.
or a loose/dirty wire at the battery positive post.

NOTE the two wires that are bolted to the battery hot terminal post are for the fans

NOTE you can find bad connections at the CE panel fuse sockets with an IR gun any that are warm or hot had poor connectivity