Air condition fuse problems

Hi all

I have problems at my 550.

My air condition compressor had a small leak (i think inside) and the bearing inside the compressor got louder and louder over the time.
Last year i ordered a new one, the plan was to change it this spring.
Last autumn at the last days i drove the car before winter), i got a "sharp" chemical smell from the left front of the engine, i think from the compressor, and the 20A fuse of my air condition melted when i switched on the air condition system.

Now i have installed a new compressor.
When i did this, i found a diode that someone soldered inside the + wire a set this to the ground at the compressor. Why, i don't know.
The diode works "against" the + wire and was OK before i soldered the diode in the wire of the new compressor

Now the system is filled with the R134A and has pressure.
Sytem is tight.

Now i have the following problem. (The 20 A fuse is for radio and Clima)



Clima switch in position "off" :
The radio works.
I can control position of the air jets (window, top, bottom, middle, ....).
I can't control the temperature (i think this is normal).

I can use the ventilation in all positions.



Clima switch in position "on" :
The radio works.
I can control position of the air jets (window, top, bottom, middle, ....).
I can control the temperature (but this moment i don't know if the compressor works because it's to cold here in Germany).

But when i switch on the ventilation, the 20 A fuse melt.
When i switch off the clima again, the ventilation works, only the radio is dead.




Can anybody help me ?


Daniel

 

Daniel,

the diode connected with reversed polarity is a free-wheel diode, to dissipate the current that circulates when the compressor's clutch coil stops receiving current from the relay. Not a bad idea!

The fuse could be blowing when the compressor is activated due to a short circuit in its clutch coil. It happened to mine, leaking oil from the front seal of the compressor got to the coil, corroding its isolation and almost shorting it. The fuse would blow after a few seconds of operation whenever the compressor was switched on.

Stefano

 

The compressor is on always(unless you press the "STOP" button) on the HVAC panel. Even if the outside temps are less than the temps selected for the inside temp. The reason for this is to dry the air. What that means is that the air is cooled and then warmed up.

 

No, the compressor is on (i.e. its electromagnetic clutch is engaged) only when its contol unit decides that it is needed and as long as the "STOP" button is not pressed.
It cycles on and off frequently.

Stefano

 

You are of course right. But the thread writer say that it might be hard to test as the temp is colder than use of AC normally would require.. What I meant is that the compressor is supposed to be active and run even in cold temperatures...

 

Its a very unusual ac system if thats the case, my mondial system was off unless requested as are most cars. The system you mention is a comfort zone re heat system but not common.
The idea that the clutch coil is shorting sounds like a good thing to look at, as it sounds like it is earthing and blowing the fuse.

 

The Diode goes in the wire providing power to the clutch electro magnet coil. The Diode provides a one way path for the electricity, only too the coil but restricts electricity from returning from the coil which stores a large amount of electricity when in use, if you suddenly turn off the power to the compressor some of this stored electricity can feed back and damage the computer if not for the Diode, so the one way diode prevents this from happening.

If anyone needs a new clutch coil and doesn't want to pay Ferrari $4155.00 for a complete compressor with clutch you can get just the coil from a late 90s Cadillac Catera, (cost about $100.00) and put your existing Diode that you remove from your old coil inline to the power line going to the clutch coil (It must be installed in the same direction as you removed it from your old coil). General Motors also uses a Diode for this purpose but they install it in line at the fuse box. Ferrari is the only Company that I know of that installs them at the clutch.

Chuck

 

Chuck, this is great news; is it an exact replacement, or a "will fit" setup? If you have the GM P/N, would you mind posting it in our 456/550/575 Interchangeable Parts thread, here: http://www.ferrarichat.com/forum/456-550-575-sponsored-bradan/394955-456-550-575-cross-reference-interchangeable-parts-source-thread.html

BTW, how did you come by this information?

Thanks in advance!

 

John

My clutch coil got oil soaked from repairs that were done before I bought the car and would pop the fuse after about ten miles of driving but worked fine otherwise so I pulled the clutch coil off without even discharging or removing the Compressor and went down to a local A/C shop and started down the shelves opening boxes until I found one that matched except for not having the Diode.

Chuck

 

Hi

The diode was and now is installed as follows :
The + wire to the compressor is uninsulated about 5cm before the clutch.
The diode is soldered to this wire and at the other side of the diode, a new wire is soldered and goes to ground at the compressor housing.
The + wire goes to the clutch, the diode to ground (like a V)
The diode's flow direction was and is against the + flow direction.
Power could flow from ground (Compressor housing) to the + wire, but not from the + wire to ground.
For me, the function is not clear.
Is there any possibility that power could flow from ground to the + wire ???
I think no.
Chuck's description of the diode is logical, the installing at my car isn't logical.


Last autumn, the compressor had a bad chemical smell and the fuse melted.
Is it possible that the leak has destroyed the clutch and the function so the fuse melted ?

I bought the compressor in the UK for about 900 €, it has the original Ferrari clutch.
Now, with the new compressor, the fuse melts when the ventilation starts with clima button unstop, but the ventilation do not run on this 20 A fuse, the ventilation also works without this fuse (and clima postion "stop").
It had 9°C, so the temperature was to low for starting the compressor (i think).

Now i will check
- the compressor function at a higher temperature (the next days)
and also
- the function of the ventilation in position "clima unstop" after the fuse melted.


I'm afraid, that the problem last year damaged something in the clima control unit.


Daniel

 

The Diode does not go to the ground at any time or any way, it goes between the power supply (the wire coming from the dash area)and the + (positive) side of the clutch coil. And it is directional, The power will go through it one way (to the coil) but be blocked from going the other way (that is what Diodes do) keeping the electricity that is built up in the coil from bleeding back to the Controls and Computer damaging them. The other wire coming off of the coil goes directly to a mounting bolt on the compressor as a ground. Since you have had the Diode off you should take it to an Electrician and have it tested and mark the correct direction it should be installed.

To clarify. Power starts at a relay in the computer area and goes thru the dash with the wire harness coming from inside the dash into the engine compartment, and travels out to the compressor area and goes "to" and "through" the Diode and then on to the clutch coil, then through the clutch coil windings and back out the other wire on the coil direct to the ground. But remember the Diode must be installed in the correct direction or power can not feed through it.

Chuck

 

Chuck, i understand all the details you wrote.

But now i'm totally confused.

My old compressor has only 1 wire coming out of the clutch, fixed with a clip and a screw at the edge of the compressor housing and goes to a plug to the + wire from the car.
The Diode was NOT between this wire.
The Diode was soldered like a V, paralell to the wire against the power flow direction a goes to the ground screw of the compressor.

Also the new compressor has only 1 wire, only the plug was a little bit bigger than the original.
Normally, i could connect the compressor with the one and only + wire, but i thought i solder the Diode exactly like at the old compressor which worked the last 7 years, even though i didn't understood the function of the diode.

Watch my scetch, it's exactly the connection at the old compressor (and the new)

Daniel
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Daniel

On yours with only one wire the Diode should be in + wire and not grounded. The original Ferrari setup grounded the clutch coil internally and when you bolted the Compressor in place it became grounded. The replacement Coil I used had two wires and you used one as the power wire with the Diode and grounded the other. It has worked fine for the past 3 years here in the Las Vegas heat.

Chuck

 

OK Chuck
Curious who soldered the diode at my old compressor.
Honestly, it looked not very professional and there is no sense in this installation.
You described the function very well, also for non electrical experts like me.

Waiting for warmer weather, i will check the compressor without ventilation.
But it seems that i have to change the installation of the diode like you described.

Many thanks, Daniel