casm Posted July 12, 2009 Share Posted July 12, 2009 Before I get into this, I just want to point out that I'm not looking to do this to compensate for a cooling system with problems; I just want to improve the rate at which the coolant is cooled when the fan has to kick in. With that in mind: I have a semi-finished (evaporator's not installed) A/C installation in my Brat. The A/C fan is mounted and operational if connected to a +12V source. I'm dithering on whether or not to finish the A/C installation, but I would like to put that fan to good use in the meantime. Basically, I'd like to have it kick in a second or two after the main fan comes on and run until the coolant is back down to normal temperature, at which point both fans would shut off. The idea behind doing it this way is to help keep electrical load down: two small kicks (one from each fan) is better than one huge one. Has anyone done this before? I've searched, but couldn't find what I was looking for. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 12, 2009 Share Posted July 12, 2009 To get it to kick in late like that you would need a 12v delay timer, and a relay.... at least. GD Quote Link to comment Share on other sites More sharing options...
Txakura Posted July 12, 2009 Share Posted July 12, 2009 doesn't Schmuck's have Imperial brand thermostatic fan controllers? you could set one for 185 one for 190, or something like that, to let one work as an aux fan for higher temps Quote Link to comment Share on other sites More sharing options...
casm Posted July 12, 2009 Author Share Posted July 12, 2009 (edited) To get it to kick in late like that you would need a 12v delay timer, and a relay.... at least. Mkay, good to know. This is a project I'm totally unfamiliar with doing, so any pointers are definitely useful. doesn't Schmuck's have Imperial brand thermostatic fan controllers? you could set one for 185 one for 190, or something like that, to let one work as an aux fan for higher temps That would probably work, though (unless I've misunderstood) I'd prefer to not have to mess with the main fan's operation if possible - what I'm getting at is that I'd like to keep the main fan working as it does now, then have the A/C fan kick in once it realises that the main fan is running. I'm guessing that this is what GD was getting at, but if you've got any part numbers or links to the one you're talking about I'd appreciate it - we don't have any CSK stores out here, just AutoZone and Advance Auto. Hell, the nearest Pep Boys is 90 miles away. Edit: Txakura, I see what you were getting at with the switch, and I think you may have just found something else that the previous owner didn't add into the mix when he was installing A/C on this Brat. OK, so it looks like what I need to do is install that switch, then put the delay timer between the main fan relay and its relay (which probably isn't there). Oof. That's not a huge deal in and of itself, but I wish I had an EA-81 with A/C I could look at to figure all of this out. The chances of one of those turning up in the junkyards around here are about zero, so it's going to be interesting. Edited July 12, 2009 by casm Quote Link to comment Share on other sites More sharing options...
Txakura Posted July 12, 2009 Share Posted July 12, 2009 (edited) Hayden Fan Control Kit Part Number: 3652 $25.99 (preset temp), 3647 (adjustable temp) $35.99 from CSK's website that would give you the #1 then #2 fan when the temp load was high, but keep it to single fan when it was more easily cooled and the second wasn't needed - reducing electrical load edit > * you wouldn't need a delay timer with the second thermostat set a bit higher than stock, I would wire the second fan's power source to a relay off of the battery or a bus bar < I have looked into this myself, (it's on 'the list') Edited July 12, 2009 by Txakura Quote Link to comment Share on other sites More sharing options...
casm Posted July 12, 2009 Author Share Posted July 12, 2009 (edited) Hayden Fan Control Kit Part Number: 3652 $25.99 (preset temp), 3647 (adjustable temp) $35.99 from CSK's website that would give you the #1 then #2 fan when the temp load was high, but keep it to single fan when it was more easily cooled and the second wasn't needed edit > * you wouldn't need a delay timer with the second thermostat set a bit higher than stock, I would wire the second fan's power source to a relay off of the battery or a bus bar < I have looked into this myself, (it's on 'the list') Bullseye; that is exactly what I'm looking for! I've got a 185-degree thermostat in there now, so could set the secondary to around 195-200 degrees and get the delayed kick-in I'm looking for. Thanks; I figured there had to be a way to do it but had no idea what to look for. Much appreciated! As an aside, someone had fitted a mystery Subaru radiator to my last Brat - it had two (possibly three, I forget) rows and used a 16psi cap. Even in start-stop traffic in 110-degree weather in Los Angeles, that little sucker just stayed right on the line on the temperature gauge. My best guess is that it was an XT6 or SVX radiator, but I just don't know - and with the compressor and pulleys eating up more space between the engine and radiator on this one, it doesn't look like something I can really do on this one. Edited July 12, 2009 by casm Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 12, 2009 Share Posted July 12, 2009 (edited) If you want seperate thermoswitches for the fans, that's fine - but where are you going to mount it? I don't like the surface mount style units. I think those are gay. I would use the stock thermoswitch - use it to control a relay that in turn trips on both fans. If you upgrade the alternator it won't have any trouble running both at the same time. Besides - the stock AC equipped EA81's ran both fans with the 50 amp alternators. I have one in my wagon and it runs without issue. The stock thermoswitches are set for 95 C, so 203 F. You want them about 8 to 10 degrees above the thermostat. I doubt your Brat had a "mystery" radiator. All EA81 radiators are two-row units. There was a cap style change in '83 so you may have seen something you didn't recognize. My '83 hatch has a replacement radiator in it with the older style cap and automatic transmission cooler pipe. You just have to know what you are looking at. I don't know of any other model radiator that will easily fit the EA81. GD Edited July 12, 2009 by GeneralDisorder Quote Link to comment Share on other sites More sharing options...
casm Posted July 12, 2009 Author Share Posted July 12, 2009 If you want seperate thermoswitches for the fans, that's fine - but where are you going to mount it? I don't like the surface mount style units. I think those are gay. Good question, and I'll figure it out after it's back from getting the clutch, axles, and struts done. I would use the stock thermoswitch - use it to control a relay that in turn trips on both fans. This is what I'd like to do. Basically it looks like there're two options: the surface-mounted thermoswitch (easy) or tying in to the existing system (not particularly difficult, but not as clear as to how to do it). If I can find a delay relay, that one's a no-brainer - but it all comes down to finding that delay relay. If you upgrade the alternator it won't have any trouble running both at the same time. Besides - the stock AC equipped EA81's ran both fans with the 50 amp alternators. I have one in my wagon and it runs without issue. Point taken. I have a spare alternator I'd like to have rewound for about 75 amps so I can run the spotlights as well as everything else at the same time; looked into the Maxima swap, but the problem is finding a Maxima in the junkyards around here. The stock thermoswitches are set for 95 C, so 203 F. You want them about 8 to 10 degrees above the thermostat. Good to know; thanks. I doubt your Brat had a "mystery" radiator. All EA81 radiators are two-row units. There was a cap style change in '83 so you may have seen something you didn't recognize. Entirely possible; my Brats have been an '86, an '85, and another '86 in that order. Thing is, someone cut (IIRC) the crossmember / panel normally between the grille and radiator to get it to fit. This sucker was *thick*, and I was surprised by the pressure it had to run at. Not discounting what you're saying... Just that it looked like something that wasn't originally there. My '83 hatch has a replacement radiator in it with the older style cap and automatic transmission cooler pipe. And this one had the auto tranny lines as well. You just have to know what you are looking at. I don't know of any other model radiator that will easily fit the EA81. Point taken, and to a large extent I don't know what was in there. I wish the person who bought that old Brat of mine up in Seattle (white, sold on Mercer Island about 2 months ago) would get on here so I could needle them on it Quote Link to comment Share on other sites More sharing options...
casm Posted August 6, 2009 Author Share Posted August 6, 2009 Okay, made an interesting discovery today. In front of the battery (between it and the headlamps) is a single yellow wire with a female bullet connector on it. If I connect that wire to the positive side on the A/C fan, both fans come on. If I ground it, only the main fan comes on. What have I found? I'd like to tap this if possible - I'm just not sure of the best way to do it. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 6, 2009 Share Posted August 6, 2009 That is the connector for the thermo-switch that controls the main fan. It is designed to be the ground for the main fan - the thermo-swtich grounds that lead when it hits the required temp. As for the AC fan coming on if you apply 12v to the ground circuit of the main fan.... I would have to look at the schematic but I'm assuming they share the same ground and you are back-feeding the circuit by applying 12v to it. Obviously the circuit is not diode protected. Don't do that anymore - it's not appropriate and you could easily hurt something doing stuff like that. As a general rule - green, yellow and combinations of the two are nearly always ground leads - sometimes black is ground as well. Red, black/red, and black/white are almost always hot leads. Those are general guidelines and they are NOT always adheared to so have your schematic and DMM handy at all times. All you have to do is plug that yellow lead into a thermo-switch in the radiator - then you pull the hot lead off the main fan, use that lead to close a relay. Run a seperate fused power lead off the battery, through the contacts on the relay and to both of the fans. When the thermo-switch closes it will energize the relay and power both fans. Start out with a 20 amp fuse and take an Amp reading on each fan - add the two readings together and add a couple amps to find what fuse you should be running in your power lead to the fans. GD Quote Link to comment Share on other sites More sharing options...
monstaru Posted August 6, 2009 Share Posted August 6, 2009 (edited) i will attest to the fact that the there are color changes in these wires.most of the ones i have found have been either straight opposite from what they were before,or different colors altogether . ,but have found it to be true in wagons and brats. specifically the years from 83-84 wagons,and 86-87 brats. defenitely get the schematic for your vehicle. cheers, brian Edited August 6, 2009 by monstaru cause i'm a *********************..... Quote Link to comment Share on other sites More sharing options...
casm Posted August 7, 2009 Author Share Posted August 7, 2009 (edited) Taking all previous advice on board: i will attest to the fact that the there are color changes in these wires.most of the ones i have found have been either straight opposite from what they were before,or different colors altogether . Good to know. defenitely get the schematic for your vehicle.cheers, brian Agreed, and will do. Thanks. I think that what I'm going to do is tap the positive for the main engine fan, wire a relay to it in parallel, and connect the positive on the A/C fan to the relay. I did some math, and the electrical system should be able to cope with the startup hit of both fans. Actually running them won't be an issue; it's just the startup I'm concerned about but it should be OK. I'm also going to go back to the OEM thermostat. It's currently an Autozone generic replacement (Stant, IIRC), and I'm not happy overall with its performance. It works, but its concept of 180 degrees seems to be somewhat flexible. I'm not overheating by any means, but the needle's not always holding the middle mark either. Edited August 7, 2009 by casm Quote Link to comment Share on other sites More sharing options...
casm Posted August 7, 2009 Author Share Posted August 7, 2009 And... At least my cooling problem isn't the thermostat: it's apparently the thermoswitch for the main fan, at least as far as I can tell - it packed up this afternoon and the needle got perilously close to the red. Jumpering the fan to the battery showed that the fan was working, so I'm assuming it's the thermoswitch, anyway; the fan wasn't coming on at all with the engine hot. I'm jumpering it straight to the battery for now as a limp-along... New switch comes in Thursday. Grmph. Quote Link to comment Share on other sites More sharing options...
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