A/C blowing hot - W124 coupe

[steve moores 1]

The recent spell of good weather has given rise for the need to use the a/c, however, mine when set to the coldest setting is blowing hot.

The system was apparently topped up approx 2 months ago. Both the fans spin at high speed and the compressor turns, however, the metal "disk" (plate) on the front of the compressor spins for 2 seconds, then stops whilst it makes a "pumping" type of noise - or the other way around-, then spins for 2 seconds then stop, etc and repeats this cycle when the a/c is switched on. :?

Can anybody advise if this is normal and if it is, what direction I should be looking in? Thanks. :? If it isn't is this a replacement part or a delicate nudge with a hammer if something is sticking?


Steve Moores
'95 E220 coupe

 

[dieselman]

The air con compressor is not staying on for some reason, possibly due to the rotational sensor detecting belt slip.

The heater blows hot because the air entering the car is heated again after being chilled otherwise you would freeze.

You could try feeding 12V directly into the compressor clutch to force the compressor to run, at least you could then test the actual air con system.

 

[steve moores 1]

Thanks Dieselman

Am I right to assume that because the engine has a small idling problem (ECU perhaps - I've tried cleaning the inside of the plenum) then the sensor detecting the speed of the engine (possibly at fault) will have a detrimental effect (safety induced) on the sensor monitoring the a/c compressor. This having a net result that the a/c compressor cuts out virtually as soon as it starts and keeps doing so?

Having spoken to the local steelership in Croydon, they have advised that the W124 can not be plugged into a PC with appropriate software. This would leave them with the option of the pinbboard technique (similar to playing a game of "battleship") at nearly £100 p.h. (incl VAT)! OUCH! :evil:

Am I missing something here? There must be a more cost effective way. Any suggestions? :?:




Steve
'95 E220 coupe

 

[jaymanek]

Why dont you take to a merc specialist in your area?? Where about are you in the country??

jay

 

[steve moores 1]

Croydon, Surrey.


Steve

 

[jaymanek]

theres George Fraser in Wembley, but if you do a search on this forum, you will no doubt find more.....

When i was looking at convertible e220's, i came across two that had the same problem, but in those cases, i think they had had front end damage and so i put it down to the system leaking...

Anyway, good luck!


Jay

 

[wagamama]

you could also try s.g. smith in crystal palace... they might be able to help...

 

[dieselman]

I'm not sure about this, but I believe the belt slip sensor uses the crank angle sensor and / or alternator, allied to the aircon compressor speed sensor. Make sure the belt is tight.

 

[R22]

A/C blowing hot

STEVE MOORES,
All a/c systems are protected by H/P (high pressure) switches and L/P (low pressure) switches amongst other preset parameters.
If a system detect too high a pressure--i.e. blocked condenser or say seized condenser fan motors/ additional engine fan motors, then the feed to the compresor coil is cut to prevent the compressor grenading itself.
Similarly, if the system detect a low pressure from lack of gas, or say a blocked expansion device(less likely) then the feed to the coil is cut to prevent the compressor seizing and / or sucking in moisture and foreign matter.
DO NOT directly feed the coil unless you have a set of gauges connected, because what may start of as a reletively cheap fix MAY hurt your wallet!!

You describe what is typically known as L/P cycling -- you have a leaky system

 

[steve moores 1]

Thanks for all the advise chaps.

Certainly measuring the refrigerant / pressure testing the system seems to be a way forwards after checking the belt tension.

Out of interest does anyone know the company Steve Redfearn Motor Co Ltd in Wimbledon? They advertise in the club magazine. :?:

I've also heard of something costing between £300 - £400 on the injection side of things (ECU - but not quite) which could be at fault. Apparently it is only capable of being checked by substitution - typical - however not many specialists carry them. Does this ring any bells? :?: or am I "blowing in the wind"?




Thanks


Steve
'95 E220 Coupe

 

[steve moores 1]

I have just got around to having the refrigerant measured, and it measured exactly as shown on the slam panel adjacent to the bonnet catch, (0.8kg).

When I took the car to Steve Redfearn Motors of Wimbledon he advised that the system should have been charged with 1.0kg of refrigerant and that the figure quoted on the slam panel was incorrect. He confirmed that there wasn't a leak to the system. He also drained the oil from the compressor and re-filled it with the correct quantity (there was far too much installed) and changed a few seals / valve inserts, etc. The system now works fine (only 48hrs of use so far).

Now at least I have the a/c working prior to going on vacation.

Thanks for all the advice.

Is this a relatively common issue? :?:



Steve
'95 E220 Coupe