Questions about Alternator and Aircon

[Lazy-Ferret]

OK, silly question time....

Firstly, anyone know what the switch on the rear end of the aircon compressor is, and how it works...

Mine is showing short circuit, but when my aircon compressor died, it ground away the electro magnet, and made a lovely short circuit, so I think it may have killed the switch as well... I eventually managed to get the switch out of my compressor, but it looks more like a "Hall effect" switch, rather than a pressure switch, which I was expecting.

I got a cheap replacement compressor, off of a car that had "supposedly" only done 61K, put it all on, but the clutch will not pull in, when I checked the switch on the rear of the compressor, it reads "Open Circuit", even with the engine running. I have bypassed the switch, and everything is working, but obviously the switch is there for a reason, I just do not know what.

Second question... The Alternator... Should it really get hot enough to burn your arm???

 

[RJL Services]

i think that the switch is to engage the clutch so as to drive the ac compressor not sure on the heat thing but most get hot due to being near the engine

 

[Lazy-Ferret]

i think that the switch is to engage the clutch so as to drive the ac compressor not sure on the heat thing but most get hot due to being near the engine

Do you know how the switch works? e.g, is it open circuit until the pump is running, or closed circuit, and some condition within the pump sends it open circuit?

There is absolutely nothing about it in the service manual, following their fault finding, it would have me replacing the clutch magnet!!

With regards to the alternator, I am sure it was hotter than the engine, but I will double check that, I have never noticed how hot they get before...

 

[RJL Services]

not sure how the switch works but my altenator gets hot enough to burn if touched if it helps rick may be able to help with switch

 

[Lazy-Ferret]

not sure how the switch works but my altenator gets hot enough to burn if touched if it helps rick may be able to help with switch

Cheers... that's good to know about the alternator.

 

[panelbeater]

could the faulty air unit be drawing to much from alt,just an idear.

 

[Lazy-Ferret]

could the faulty air unit be drawing to much from alt,just an idear.

Fortunately, no, I noticed how hot the Alternator was, before the Aircon was connected back up, otherwise I would have been paranoid.. :nenau

I have done a bit more searching on the web, and it seems to be a common question, lots of people do not realise just how hot an alternator gets, and I was one of them.

 

[kitchenman]

Over 800 watts so quite hot
70 amps x 12+ volts if I got my sums right

 

[solarman216]

Re your compressor switch, I was always given to understand the the switch on the accumulator is the low pressure switch (ie no gas=no compressor run) and the one on the compressor is the high switch(ie if the system has a blockage, as in ice) then this also stops the compressor from destroying itself, Rick

 

[Lazy-Ferret]

Re your compressor switch, I was always given to understand the the switch on the accumulator is the low pressure switch (ie no gas=no compressor run) and the one on the compressor is the high switch(ie if the system has a blockage, as in ice) then this also stops the compressor from destroying itself, Rick

That would make sense, although, I can't work out how the switch works, as it does not seem to have any bits that move.

The Workshop manual, implies that the high and low pressure switch is a singe switch in the condenser, but I do have to say it has a sever lack of practical info when it comes to where things are, and what they look like.

How likely in this country is the system to ice up? I have been running it today with the switch bypassed, and it working a dream.

 

[solarman216]

No the ice is within the system, ie moisture in the refrigerant due to not being vacced down enough prior to charging, it can form an ice plug that stops the compressor dead, Rick

 

[Lazy-Ferret]

Well, after spending 2 nights searching on google etc, I have eventually found out this particular sensor on the end of the DKV 14c aircon pump is actually a thermal protection switch. It protects the pump should it get too hot.

The one on my old compressor was so tight, the brass edges of the body rounded off while I tried to remove it, but I did eventually get it out with a set of molegrips. I used the wiring off of it, to put in a bypass on the replacement compressor, to prove everything else was working.

Tonight, I set it up with the continuity meter on it, and then used the soldering iron to heat it up. I discovered that when it gets to about 100c, it shuts off, then once it has dropped back to about 85c, it turns back on again.

The problem now is, where I get a replacement one from, and if I can get the one out of the replacement aircon pump, while it is in situ.

Please to know that temporarily running without it should not be a major issue though.

 

[solarman216]

Should not be a problem Clive, and the Mrs motor still has the compressor on it but no belt or air con rad, I assume the switch to which you refer should still be on it, if so you are welcome to it if it is the same, probably not be able to look at it till the W/E, Rick

 

[Lazy-Ferret]

Should not be a problem Clive, and the Mrs motor still has the compressor on it but no belt or air con rad, I assume the switch to which you refer should still be on it, if so you are welcome to it if it is the same, probably not be able to look at it till the W/E, Rick

That would be great Rick.

It must be there for a reason, although it's fitted as standard by Zexel, who make the pump, rather than specially for Nissan, but would still be nice to have it there "Just in case".

Its a 19mm nut, right at the back, on the top of the compressor, behind the rear pipe. I think it might be a real pig to get to with the pump in place though, but might be easier for you, as you have the ramp.

It has 2 wires coming out, one goes up to a connector that hangs just under the alternator, and the other wire goes to a connector that is clamped to the side of the aircon pump, which then in turns connects to the clutch magnet. the connectors will just pass through a 19mm ring spanner, but I only have 16 point ones that grip on the nut corners. Ideally you need something like a Glowplug socket, as you want a 6 sided socket to get a good grip, but need somewhere for the wires to come out.