Air con issue - W124 E320 C - 1994

[MotardMan]

I picked up our (new to us) car, on Saturday to be greeted by the dealer telling me they had not got the a/c repaired as promised. He has asked me to get the system sorted out, and bill him for the work.

So, does anyone have a recommendation for a competent agent that can sort out why the compressor is not engaging even though the "dealer" has (allegedly) pressure tested and gassed the system?

The blower refuses to do anything but blow hot, not nice when outside is 27 deg C!!

I predict OVP is going to get mentioned, as wil the control panel for the heater controls... This car does not have the full CLimate, but does have the vertical row of 3 buttons for EC, Dehumidify and recirc.

Fangs in advance..

 

[MotardMan]

Oooh, I should mention the area I need this service is Aztec West, near Bristol, M$/M5 Junc if possible........

 

[shj]

I had a simular problem with mine,my Inderpendant suggested fitting a dedicated in line fuse which he did, no problems since,apparantey the overheating of the blower fuze in the fuze box of the late 124s is a common problem.

 

[MotardMan]

Excellent.

Is there a way of testing the compressor function by jumping it directly?

 

[shj]

I'm afraid I don't know

 

[jibcl500]

if the gas is low the compressor wont kick in, try kwik fit they do a regas at £40 no fix no fee. But check your fuses first, my dads CE AC fuse was blown and MB didnt find that even after charging £300 to fix his AC, which they didnt fix !!!

jib

 

[MotardMan]

It is gassed up, apparently.... They had to vent the gas wen the cyl head was done, and got a local place to regas and pressure test the system. Fuse in bay 7 looks and tests all OK.... I'm praying it is not the control head on the dash. Mind you, if it is, the dealer has said they will pay to get the A/C running, so they can foot the bill......

 

[Bolide]

You can jumper the low-pressure switch to try and get the compressor to kick in. But it'd be best to get an expert to work his way through the whole system

Whoever gasses it must check to see if it's a factory system or a retrofit. The retrofits can take a different weight of gas

Unfortunately I've not met anyone so far who knows these systems inside out

Nick Froome
www.w124.co.uk

 

[Andy Wr]

It is gassed up, apparently.... They had to vent the gas wen the cyl head was done, and got a local place to regas and pressure test the system. ....

Report them to the environmental health and watch their faces as they are prosecuted and fined £20,000.

 

[Parrot of Doom]

Is it blowing roasting hot air, or just warm un-airconned air? If the former, consider the duovalve (see DIY section of forum).

 

[c955]

Is it blowing roasting hot air, or just warm un-airconned air? If the former, consider the duovalve (see DIY section of forum).

What if it's the latter, just warm un-airconned air? Likely diagnosis?

 

[Ade W124]

Took the CE to Kwik Fit this morning for a regas.. A/C currently blowing at 14C, the mechanic fired up their system, has 300E, TE but no CE??? and then after 20 minutes of poking round under the bonnet with a torch, he couldn't find the valve to connect to.

Looks like I'll have to take it to a specialist..:roll:


bet it'll be more than £44....

Ade

 

[carabind]

14c is a bit high. It should be under 10c as a min - have seen sone a/cs go down as low as 5-6c measured at the vents. A good indie might be able to recommend someone who have experience of MB ac

 

[MotardMan]

Is it blowing roasting hot air, or just warm un-airconned air? If the former, consider the duovalve (see DIY section of forum).

Sorry for the late responses. Daughter turned 5 this weekend, so we have been REALLY busy.

It is odd as the heater WAS blowing roasting hot air, but now varies. I've tried to pick up a pattern here, of what happens when do make adjustments, and this is how it appears to (mis)behave.

EC button on (red light), cool air from centre vents, hot air from drivers vent and warm from the passenger side. Both wheels set to 18C. If you set them to the blue dot, no change.
The temp does vary a bit, but not in line with the wheels...
I have tested the air temp sensor by the light and air is being drawn in the vent so it is not the blower motor beihnd the passenger air bag. (Phew!).
EC button off, HOT air out of everything!

I reckon the duo valve could well be the issue. Are they expensive?

 

[MotardMan]

14c is a bit high. It should be under 10c as a min - have seen sone a/cs go down as low as 5-6c measured at the vents. A good indie might be able to recommend someone who have experience of MB ac

I have a chap coming in to work on the 22nd June to give the whole system a health check. He is both a vehicle sparks, and an aircon guy, so I'm hoping he will be able to fault find the whole darned thing. I'll certainly post up what he finds and the actions taken to remedy.

If you need a boke in the Bristol/Glos area, then you could do worse than look up Go Cool and speak to George.

The other company that came recommended by a neighbour, is AMA Air Conditioning in Nailsworth. However, 2 emails and a phone call have not elicited a response from them to me, yet, other than a request from them for my telephone number..

 

[Bolide]

Sounds like the Duovalve. They are expensive new

I don't know if they go hot or cold when you take power off them. It'd be worth pulling the feeds off the Duovalve and seeing how the system works then

If the Duovalve is bad then your a/c guy can't do much. You might be better fault-finding & sorting the Duovalve before getting him out to the a/c

Nick Froome
www.w124.co.uk

 

[MotardMan]

Sounds like the Duovalve. They are expensive new

I don't know if they go hot or cold when you take power off them. It'd be worth pulling the feeds off the Duovalve and seeing how the system works then

If the Duovalve is bad then your a/c guy can't do much. You might be better fault-finding & sorting the Duovalve before getting him out to the a/c

Nick Froome
www.w124.co.uk

Hi Nick,

Thanks for the reply. OK, done some car park fettling and found the vlaves in the duovalve do click when you pull the plug off the assy. So there is voltage at the duovalves. I also tried winding the temperature up to max on both sides and felt the air get increasingly hot as the valves opened up and let the water through. Turn the wheels back down, and the air cools to ambient. It seems to happen very slowly, and I'm guessing this might be due to the pump not working:

I'm assuming the pump is the cylinder behind the duovalve? I have no test lamp or multimater here to verify voltage at the pump, but cannot "feel" it running when I remove and reseat the connector on top of it.... All of these "tests" were done with the a/c set to "EC". If you take EC off, the centre vents blow hot. The fan also speeds up when you select recirculation, so it would seem my control panel is OK....

Have any of you any more tests I can do to prepare myself for Friday? Anything I have missed?

 

[Ade W124]

Have very similar issues to you Motard.. Lots of heat, very little cold without AC on.. also big time lag between hot to cold.

Be interested to see how it pans out. (could be the spider)

Ade

 

[MotardMan]

(could be the spider)

Ade

I'll be sure to let you all know what the man says. As for the spider, he or she, is more dessicated than a dessicated coconut on dessication island in a drought.

;o)

 

[MotardMan]

The quote is in!

Very nice and competent chap from Go Cool came out to see the car. This is what we and he found out.

A broken wire in the connector to the speed sensor on the compressor. Repaired it on the spot so the compressor now runs. Excellent.

Gas was analysed as R134a and was free of air. Good news.
Condensor is leaking, Bad news.
Filter drier requires replacement as part of replacing the condensor. Bad news.
HP port is leaking, bad news.
He also noticed the serpentine belt is WELL past its best with cracking on the flat side, and worse the ribbed side has chunks missing and is cracked.

Even though the compressor now runs, the car still only blows hot from the drivers vent. We clamped off the output hose from the heater matrix to prevent the heater from receiving hot water as if the temp dials were set to cold, and the vents all blew cold down to between 5.8 and 11 deg C. Excellent.

So it seems the duo-valve is broken.....

As the dealer had agreed to sell the car with a working a/c system, and pay for the remdial work, I suspect he will be perfectly happy about the bill for £785 to fix it all........ Don't you? Especially as his "specialist" a/c man said all it would require was a thermo switch. I'm especially upset that the car was supposedly serviced before I picked it up, and the belt was not noticed? If this snaps then I lose PAS, alternator, cooling......

I'l let you all know the result.