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240 '91 240 What is this and how do I fix it?

ZVOLVO240

Active member
Joined
Mar 30, 2008
Location
MD
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This is found on the driver's side of the powersteering bracket.

It has a black wire running from it, under the pulley. It is connected to a green wire in the harness via some sort of bullet plug.

Anyone know what this thing is, what it does, and where to get a replacement?

I just noticed that the wire has been completely frayed off from the right side of the green cube.

Help :omg:
 
IIRC, that is for "noise suppression" of the compressor in the electrical system.

If you already have an aftermarket radio then it's likely of no benefit to replace (as many newer electronics can filter out noise like that.)

Maybe someone else can help with exact info for a replacement.

HTH?
 
ok so its either AC or radio?

My radio is working fine but I have not used my AC yet.
 
It's best to have the diode, but the a/c will work without it.
You can either get a used one from j/y, or as I did once, dremel away the potting and solder in a new wire to the lead (if the lead is too short to solder to directly)
These are not available through Volvo except when buying a new compressor (clutch). There are some aftermarket diodes that can replace it, but the j/y route is the best way.
 
it's not really necessary to have it.

Well, I think you should reconsider that statement.

Will the compressor clutch work without it? Yes.

How long will the compressor clutch work without it? ???

How much longer will the compressor clutch last with this diode in place? A whole freaking lot longer.

That is the reason that I rescinded my original remark.

It does potentially suppress any popping due to compressor engaging, but the actual purpose is to keep the inductive flyback from the compressor disengaging from welding the clutch center and outer pieces together.

The link that I originally posted to Wikipedia should be a good place to start.

jjh242t nailed it. And, I wouldn't drive around with a working compressor intentionally shortening its life ;-) (or at least the life of the clutch - which in most cases: clutch = compressor)
 
Well, I think you should reconsider that statement.

Will the compressor clutch work without it? Yes.

How long will the compressor clutch work without it? ???

How much longer will the compressor clutch last with this diode in place? A whole freaking lot longer.

That is the reason that I rescinded my original remark.

It does potentially suppress any popping due to compressor engaging, but the actual purpose is to keep the inductive flyback from the compressor disengaging from welding the clutch center and outer pieces together.

The link that I originally posted to Wikipedia should be a good place to start.

jjh242t nailed it. And, I wouldn't drive around with a working compressor intentionally shortening its life ;-) (or at least the life of the clutch - which in most cases: clutch = compressor)

So you wouldn't drive the car? If I do whats going to happen until I fix it?

Its an auto btw.
 
Well, I think you should reconsider that statement.

Will the compressor clutch work without it? Yes.

How long will the compressor clutch work without it? ???

How much longer will the compressor clutch last with this diode in place? A whole freaking lot longer.

That is the reason that I rescinded my original remark.

It does potentially suppress any popping due to compressor engaging, but the actual purpose is to keep the inductive flyback from the compressor disengaging from welding the clutch center and outer pieces together.

The link that I originally posted to Wikipedia should be a good place to start.

jjh242t nailed it. And, I wouldn't drive around with a working compressor intentionally shortening its life ;-) (or at least the life of the clutch - which in most cases: clutch = compressor)

So you wouldn't drive the car? If I do whats going to happen until I fix it?

Its an auto btw.
 
Well, I think you should reconsider that statement.

Will the compressor clutch work without it? Yes.

How long will the compressor clutch work without it? ???

How much longer will the compressor clutch last with this diode in place? A whole freaking lot longer.

That is the reason that I rescinded my original remark.

It does potentially suppress any popping due to compressor engaging, but the actual purpose is to keep the inductive flyback from the compressor disengaging from welding the clutch center and outer pieces together.

The link that I originally posted to Wikipedia should be a good place to start.

jjh242t nailed it. And, I wouldn't drive around with a working compressor intentionally shortening its life ;-) (or at least the life of the clutch - which in most cases: clutch = compressor)

I will not reconsider my statement because of the fact that here in this HOT box we call Florida, the A/C is on constantly. Will that stupid thing shorten the life of the compressor? Perhaps. The average life of a Sanden compressor in Florida is 5 years. Relays and A/C thermostatic switches are there for a reason. My personal car has a sanden without that block on it and its been no problems. Yes, are those diodes there for a reason? Yes. But in all my years doing this, Im yet to see a compressor/clutch fail prematurely because of not running that block.
 
So you wouldn't drive the car? If I do whats going to happen until I fix it?

Its an auto btw.

Nothing noticeable will happen (immediately).

So, you can continue to drive the car. I was just saying that if I had a working A/C system and all I had to do was knock out one bolt for a silly diode, I would do so because the work involved would be so much less than what would prematurely be needed if I was to say f'it.

---

My experience with flyback suppression is in security applications where magnetic door locks will kill push-to-exit switches in a matter of weeks that would normally last for years when wired a certain way and not using a flyback gate. This is due to arcing that happens in the contacts when pushing the button to leave.

A very similar thing is happening in the A/C compressor. So, eventually it will fail due to buildup of carbon from arcing. If it is always on as in RP80242GT+T's case then there isn't too much of an issue (I suppose - I would have to watch it with a scope to be sure, but likely not enough issue to cause a failure).

Again, it will be fine to drive. I would keep an eye out for a good used diode at any local junkyards that you peruse. If I were going at all in the near future I would promise to find you one.
 
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Relays and A/C thermostatic switches are there for a reason.

Your car: fine.

Maybe not for others. This is Turbobricks, not RP80242GT+T's-brick.

And, the flyback suppression has absolutely nothing to do with the relays and solenoids used to construct an A/C system.

That diode is there to keep an arc (read stream of electrons) from removing metal from one location and electroplating it in a location which would be wholly undesirable to persons not fond of a $400 compressor clutch job ;-)

And, I happen to believe that the O.P. would rather spend his money on other things than this...
 
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Your car: fine.

Maybe not for others. This is Turbobricks, not RP80242GT+T's-brick.

And, the flyback suppression has absolutely nothing to do with the relays and solenoids used to construct an A/C system.

That diode is there to keep an arc (read stream of electrons) from removing metal from one location and electroplating it in a location which would be wholly undesirable to persons not fond of a $400 compressor clutch job ;-)

And, I happen to believe that the O.P. would rather spend his money on other things than this...

We will just leave it as that. You know everything, I know nothing. 10 + years as a Volvo Master tech and I know nothing. Your theories and synopsis are fine and Im not arguing with the fact that is there for a reason. Heck we dont even know if this man's A/C is working or its on its way out. The simple fact is, to me it looks like an old compressor and if he can get another few years out of it without messing around with that block then so be it. The guy is so scared that something is going to blow up if that stupid thing isnt hooked up. I try to give a best case scenario and everybody is arguing over this stupid thing. point closed. ZVolvo, do what you think is right. forget my opinion and listen to these other guys.
 
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