inactiveuser1

I will have time tomorrow to get the car back out and take a look at the fans while running.
It may be possible 2 different things at once also or even the fans.If the fans kick on and the noise is there should I just unplug the fans for a moment to see or maybe take the fuse out as I see on 928gt.com number 28 & 29 fuses for each fan that way I could listen to one fan at a time and also have both off for a moment.
Thanks,
Mark

dprantl

Hmm, Bob is right that your car doesn't have a high pressure cut-off switch. It's just those symptoms are exactly what I've seen on other cars that have one. It wouldn't hurt to disconnect both fans for a few minutes to see if them kicking in is the cause of your RPM dip. Just keep a close eye on the temp gauge.

Dan
'91 928GT S/C

inactiveuser1

Will keep an eye on the temp gauge and will check back here later on this evening to give more info on the fans when they are unplugged.

inactiveuser1

1st had fans still plugged in let the car warm up 1/2way before the first white mark running really cool yet the fans went on and sounded good.
Then unplugged the fans let it warm up till it was under the last white mark made sure not to let it warm more than that.Air was on but with it only idling and fans unplugged air conditioning seemed less cool.Could be just from idling or does the fans unhooked have an effect on that?
With the fans unplugged it sounded ok so far (with NO clicking)temp alittle under the last white mark.
Then shut down the car and (plugged the fans back in).
Now with the fans plugged in started car back up with air on and fans on as temp was starting to come down the noise was there and if counting to yourself it was a constant ever 5 to 6 seconds you could hear the clicking sound.The tach would drop off maybe 250.It was idling almost at the last white line before 1000(750rpm)Tach drops to the middle area(500rpm no lower than 450) when it cycles.It is a constant 5 to 6 seconds when the sound clicks in andd out.
When my LH went and the injectors clicked....its almost like a real quiet single click sounding like that is the best way I can describe it.
Do they cycle that much?and if so how about the rpm drop that much also?
Maybe with stereo on before never noticed it.
Any thoughts?
Thanks,
Mark

dr bob

Mark--

You can usually see the front of the compressor under the conditions you describe. Take a look there where the belt drives the outside part of the clutch assy. With the clutch engaged the inside part spins same speed as the belt, disengaged that inside part is stopped while the engine continues to turn the belt and the outside section. Does the inside part of the clutch turn all the time, or does it start/stop with the clicking?

inactiveuser1

Bob-
I when I take it out tomorrow and warm it up again to watch it,was looking at the fans mostly earlier.
On the nose of the clutch the smallest outter diameter at the nose, watch for that or is it actually the inside of the nose area if so hard to see that.
Mark

inactiveuser1

Bob-
I did warm it up today and after it gets over the first white mark on the temp gauge by about the thickness of the red temp needle the clicking starts again.
I looked down there with a drop light and yes the front nose of the clutch stops while the rear belt area is going and then starts on and off every time when it clicks so that narrows it down.
I talked to the dealer they were more like well replace it when it goes.
Would it mean the clutch is on its way out,low or high refrigerant?Or?
Thanks
Mark
____________________
1987 928 S4 Auto

j.kenzie@sbcglobal.net

Clutch fast-cycling could be clutch itself, control unit or wiring or more likely relay.

dprantl

You can test to see if it's the actual clutch itself by disconnecting the compressor wire and connecting it to +12. If it runs all the time without cutting out, then it's an electrical problem.

Dan
'91 928GT S/C

inactiveuser1

Compressor runs fine till the car gets in a certain temperature range then thats when it cycles on and off.
Would it be more of anti-freeze switch or pressure switch?

dprantl

It could be the clutch itself. Just jumper the compressor to eliminate that possibility first. Then you can go from there and eliminate the others, such as the freeze switch.

Dan
'91 928GT S/C

dr bob

You can test the freeze switch as a possible --problem-- by jumpering between the two wires that attach to it. You can test to see if it's a --symptom-- by sticking a thermometer in the center vent and watching the actual air temp as it cycles the compressor off and on. It should shut the compressor off somewhere around 40ºF, and let it restart again after it warms a few degrees. Consider that the freeze switch may actually be doing its job, cutting off the compressor to keep the evaporator from becoming one big block of ice. With your newly serviced system, it's quite possible that you could make ice cubes if the switch wasn't working.

Simple-stupid test: Run the interior fans on high and see if the time between cut-outs increases. If so, the freeze switch is doing its job.

inactiveuser1

Bob and others trying to help out--
I tried the simple -stupid test since that was easiest for me lol.
Since the car has rear air also....
1st I tried the front only fan one 1st setting,clutch seemed to cycle ever 5 to 6 seconds.
With both the front and rear air fans on high I counted past 30 and no cycle at all.
I tried this 3 or 4 times back and forth and it did repeat cycles the llonger for the air of full fornt and rear it didn't happen with both fans on high unless I reved the throttle.
Not sure if this helps with info but while watching an controlling the throttle by hand the clutch would stop for alot longer period when reving the engine up.
It not as warm out being its later at night.When I set the air on around 80 it cycles alot
When setting it colder of course didnt cycle as much.
I only leave the climate control mostly in the 72 to 75area.
If there is any other relays or switches to try pictures would help also.
My dealer almost didnt want to work onthe car at first because he says one thing leads to another and customs are shocked at the bill.So trying to learn more about the car even thou 928's I am at the VERY early learning stages.
Thanks,
Mark

dprantl

If the air out of your vents is cold (i.e. 40 deg F or so) then your system is fine. Here's what happens in a healthy system:

1) You turn on the climate control; compressor comes on and cools the evaporator
2) Evaporator approaches freezing temperatures
3) Freeze switch cuts the compressor off
4) Evaporator temp begins to increase because compressor is off
5) Freeze switch stops cutting off the compressor, compressor turns on again
6) Go to step 2)

3) will take longer to happen if:
- The fan speed is faster
- If the rear air is on
- The warmer the setting on the climate control (excluding defrost)
- The colder it is outside

All automotive A/C systems work this way, the 928 is no different. If your fan speed is on 1 and rear air is off and it's not too hot outside, the air out the vents should be near freezing and the compressor should click on and off frequently like you are describing.

Dan
'91 928GT S/C

inactiveuser1

Dan-
Maybe since the air wasn't working as good I never noticed it cycling as much before as rpm seemed to drop off more now but then again since system wasn't working as much before rpm dropoff might not been noticed.Will check the vent temp too see how cool it is.
Later this fall I would like to get into the cam timing being its an auto would like to check it and advance the cams for more bottom end.Never tried it before on the 928 this will be interesting and of course questions,will be time to try Kens system.
Thanks,
Mark