Hi, can anyone tell me exactly where the aircon compressor relay is located on a '96 Mk1 Eunos and what it looks like please. I want to check that it is getting the right voltage when the A/C is switched on and also the output voltage is there too, but have no idea where to find the relay or what it looks like!
Also, if the voltage is getting through is there any other reason why the compressor may not be pumping - like a low pressure cut out or something - that might be activated, and if so, where might that be located. I have no real idea of the AC system and it’s component parts on this car!
There is a pair of AC relays hanging off a bracket next to the driver’s side headlamp, usually under a rubber boot.
There is a pressure switch which usually has a brown plug with 2 wires. If the system pressure is low this senses that and prevents the compressor from engaging. You can bridge the connectors in the switch and see if the system comes into life. That will confirm that it is a low gas issue.
Hi Roadster - thanks for that. Where is the low pressure switch located? I am assuming it is on the high pressure (small diameter) pipe on the exhaust side of the engine about half-way back, is that right? Will look for the relays and switch tomorrow as it is very dark now!
The pressure switch seems to move about a bit depending on the age of the car. Yes, it’ll be on a high pressure pipe. There will only be one electrical connector on the AC pipes so it’s probably the one that you’re referring to.
That’s what I thought - hence the query on where to find the relay and also if anything else (like a pressure switch) could inhibit the compressor running. Hoping to find that it is something simple, like a duff relay or lack of gas rather than the compressor or magnetic clutch. Saw the price for a new one from MX Parts - good job I was sitting down!
If it is the compressor/magnetic clutch do you know if the Mk2 compressor/clutch fits the Mk1? Autolink I think it was had a second hand Mk2 one for £95 all tested and OK, a new one is four times that!
I don’t know if the compressors are interchangeable between NA & NB or not. Some of the pipe layout is different on NB so that may dictate whether the compressor will fit or not.
The pressure switch inhibits operation of both the magnetic clutch and the fans.
Since last post I have found MX Heaven has a Mk1 1.6 Aircon compressor for £95 too - seems to be the going rate.
Both fans runs when the AC button is pressed, plus the engine speeds up and the aircon light comes on. So as the pressure switch deactivates the fans as well as the mag clutch, the finger of suspicion is pointing at the magnetic clutch, or the compressor. The next step I guess is seeing if the clutch is getting an electrical feed or not. Your advices are much appreciated, many thanks. Always better with two brains on the job!
Time for bed now I guess, will ponder more in the morning… or during the night!
As you suspect, I’d rule out a relay fault before condemning the compressor. The compressors are pretty robust. You can test the magnetic clutch by feeding it (the single wire to the compressor) with 12 volts, but be aware, it draws A LOT of current so you need heavy gauge wire and good connections. I wouldn’t power it up for more than a second or so.
Well, made some sort of progress I suppose - the compressor clutch is definitely NOT pulling in, but it is free as a bird to turn when checked, with the engine stopped of course. As you said Robbie, pretty damn obvious, pulley wizzes round but bit in the middle with an end flange stays put, stationary.
Robbie, I only found one relay hanging off a bracket behind the back of the drivers headlight. As the engine is a 1.6 I thought this must be the A/C 6 wire relay, but then found 7 wires to it, 2 very small and rest a bit bigger. I presume, because I haven’t been able to see the actual connections yet, that one pin must have two wires on it which if so could be to the 2 fans, I thought? Or does one wire go to the other (engine) fan relay? Not having a wiring diagram with me isn’t helping! So, I was wondering, would that mean the relay does both jobs, supply to the fans and to the clutch, with the very small wires being the relay operating wires?
Also found a wire coming out the loom behind the passenger side headlight that goes via a connector down to the clutch, so that will be first port of call when I am home and have access to a multimeter again (visiting youngest daughter at present, devoid of tools etc). But although I can just see the compressor itself, reaching it is something else because of all the stuff like the air filter and pipework and the hydraulic pump being in the way. Plus without a decent light it’s all black down there! Is the usual mode of access from below by removing the under-engine pan? Otherwise I need 1inch diameter hands and arms with universal joints to get there! Though removing a section of air ducting might help. I can just see, sort of, where the feed wire goes to the compressor clutch, but no sign from above of the earth wire, hence the “is it accessed from below” query.
I have no wiring diagram for the AC system so I can’t help with the wiring of the relay. I’d guess that it must control both the compressor and the fan, you’ll have to chase wire colours to confirm. The compressor grounds through it’s body so only has one wire going to it which is the 12v feed wire.
I have the manual at home written for the Miata that MX Parts sell, it’s very good but from memory a bit light to say the least on the AC system, considering it to be requiring specialists to service it which has a strong element of truth, but I am hoping that of the several wiring diagrams in the book there will be one that will help. If I can prove it’s the compressor clutch I will get a second hand one at get the garage to fit it as they have the kit to recharge the system afterwards.
Earthing through the body seemed the obvious solution to me, but elsewhere I read to check the earth link so I presumed, again presumed, that there would be an earth wire.
I hate chasing wires in cars, the colours have a habit of sometimes changing without notice!
My car does not have the two 4 pin relays mounted behind the drivers headlight but a single 6 pin relay (not replay as in the title!) in the same place. I state this to help any others faced with this system!
As far as I can see, the relay supplies the fan and also the compressor clutch via the pressure switch. That is, the wire from the relay goes to the pressure switch and then to the clutch - hence no continuity found earlier between clutch and relay!
The clutch is kicking in when supplied with a 12V supply directly from the battery, so I presume that that is all OK for the time being.
The wire from the pressure switch to the clutch shows continuity so that is OK too.
The pressure switch is open circuit however - the manual says that it should show continuity, so presumably either the pressure switch is faulty, or the system pressure too low, or the system pressure too high, whichever way the system is supposed to work! So the next step is for the garage to determine what is at fault. The system was recharged at the beginning of the season but never really worked and I was too busy to fault find until now. So there is a possibility that the gas has leaked out the system through leaky seals or whatever, we will have to see.