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A/C compressor only turning on when radiator fan turning on.
Topic Started: Jun 23 2017, 09:43 PM (305 Views)
Geogreg
GeoGreg
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Hello everyone!

So I have kind of a weird thing happening with my A/C system. I have what looks like a factory installed aftermarket A/C system when what looks to be some questionable relay wiring (A random relay is ziptied to the engine bay). So the A/C blows cold when it blows cold, the A/C fan turns on when I push the A/C button but the compressor only turns on when the radiator fans turns on. So if I get in my car I have to wait 10 minutes until the engine temps get high and the radiator fan turns on for me to actually have cold A/C.

I swear I remember at some point the A/C working all the time without this issue, but I might have just used it when the car was getting hot?

My initial thoughts are that geo metro's that didn't come with A/C factory don't have an evaporator temperature sensor (Correct me if I am wrong here) and the dealership took a short cut by wiring the A/C compressor to the engine coolant temperature sensor.

Has anyone had this issue before? Do geo metro's without factory A/C have an evaporator temperature sensor?
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geogonfa
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Just my .02...without seeing the wiring set up, and not knowing what year model...best guess... I would take the wire from the temp sensor going to the a/c and ground it...see if the system acts normal, if so, your going to need a temp cut off sensor in which mounts into the lower intake manifold just above the alternator and attach that wire to it... :type
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Geogreg
GeoGreg
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Awesome will try that! Thanks for the reply!
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Geogreg
GeoGreg
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Ok just checked some stuff out. There is one relay which a lot of the A/C stuff is hooked up to.

My model is a 1990 Geo Metro, 3/5

Here is the relay:
Posted Image

Here is the wiring going into the relay:
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The wires that are going to the relay are as follows:
Top: Compressor power, radiator fan power
Right: Blue/Red wire
Bottom: Power
Left: Nothing

If I supply power to the left position then the A/C compressor turns on and the air gets cold. When the radiator fan turns on it supplies power to that top compressor wire in addition to the radiator fan and the compressor clutch engages and cold air comes out of the vents.

Not sure how it is intended to be set up, but it doesn't seem like the radiator fan and the A/C compressor clutch should be hooked up in any way?

Is this the AC temp sensor (Ignore the horrible wiring)? Should this shut off the compressor if the A/C lines get too cold?
Posted Image

Edited by Geogreg, Jun 25 2017, 07:29 PM.
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JellyBeanDriver


That's a low pressure cutout switch. Should be closed except when you have a leak. BTW, you make have dealer installed aftermarket AC but someone hacked up the wiring.

The 12v power source should come from the blower circuit. Blower on = source for coil on relay.

At this point you should just rewire it correctly. My original AC, there was a thermostatic switch with bulb on the evaporator. You'd string that in series with the blower +12V, in series with the low pressure cutout switch then to the relay that drives the condensor fan and ideally another relay to the compressor coil.
Edited by JellyBeanDriver, Jun 26 2017, 12:14 AM.
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bkgeig
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I've spent way more time than I'd like diagnosing and repairing my AC. Where are you located? I'm in Socal, Riverside.

I'd recommend returning this to stock and then debugging from there. The fuse box is on the drivers-side fender wall. Inside is one 15a fuse for the AC system. That feeds 2 relays, also in the fuse box, one for the compresssor and the other for the condenser fan. Is all that stuff in your fuse box?

There are a number of ways the AC cuts out, some in the cabin and some in the engine bay. Not all are necessary, in my opinion, especially if you monitor engine temp.

Here's a link the '94 factory service manual: http://geometroforum.com/topic/5044844/1/#new

Here's a link from the FSM to diagnosing the AC electrical. I'd spend some time familiarizing myself with it. It looks more complicated than it really is: https://docs.google.com/file/d/0ByZnrvyffe1KS25OajhCYVo4bzg/edit
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Geogreg
GeoGreg
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Thanks so much JellyBeanDriver and bkgeig! After reading a ton and following the all the wires to the A/C I have come to a similar conclusion as you two. I am going to be stripping out the wiring as it is now and doing it properly. Started reading through all the factory wiring diagrams for how the stock A/C works and with that and your awesome comments I feel like I have a good understanding of how the A/C should be wired up now.

Going to tackle wiring it up soon so my A/C is not so intermittent :p

Thanks again!
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