A/C problem intermittent and throttle body issue

[globalgrooves]

So i have been having ac problem for a while, finally got my buddy a Merc tech to look at the car today. My car is 1994 E500

Problem is sometime ac works and sometimes it doesn't. When working everything is fine and very cold. More often than not it does not work at all, it has become progressively worse over a period of about a year. Switching car off, and on doesnt change anything, switching the button no luck either.

My tech friend came back said i may have a couple of problems, first the throttle body was fluctuating up and down 100 rpm, and that could cause the sensor inside the AC compressor to not switch on, and/ or the sensor in the ac compressor is bad. The throttle body was changed a few years ago by the PO (at great cost) so what can be done to fix the rpm fluctuation without replacing the throttle body ideally !!
thanks
neil

 

[gsxr]

First you need to pull all codes, clear all, and then check codes again after the AC acts up. If there are no codes at all, then we go into wild guessing model.

The RPM fluctuating should be irrelevant. The BM compares engine RPM to compressor RPM, they should fluctuate together. I'm assuming the serpentine belt is tight / tensioner working. If the ETA was already replaced with new, it is extremely unlikely to be defective. More likely that you have a vacuum / intake air leak causing the idle fluctuation. If the ETA was replaced with used or rebuilt, it's somewhat questionable but still unlikely to be related to AC performance. The sensor on the compressor could be bad, also check the wiring to the compressor, and the wires on the compressor itself to the speed sensor on the rear.

 

[globalgrooves]

ok i will chek that out, wires are supposed to be all good, belt is tight and so it the tensioner. ETA was new when fitted, do they sell the speed sensor separately ?

 

[gsxr]

IIRC, the compressor speed sensor (aka tachometer) is not sold separately. But, you might be able to swipe one off a junkyard compressor? I forget if they are a simple R&R or not. Never done that, can't recall offhand reading of anyone else either. I'd rule out other stuff first.

The new ETA is probably fine, btw.

 

[globalgrooves]

cool thnx gsxr !!