I'm planning on adding a fan in from on the condenser on my '82 245, and would appreciate any suggestions about the best way to wire it up. I plan to use a relay powered up by the compressor clutch circuit, and also thought I would try to wire it through the 4th gear switch or the OD circuit so that the fan would cut out once in 4th gear. Any ideas would be very much appreciated. Thanks again in advance for your help.
Steve.

Wow. Great minds think alike. Recently, having repaired the air on our 83, 90 and 91 240's, I was amazed at how much more efficient the later cars are. Condensor style is similar, and certainly the 83's condensor is older and not as pretty, but the difference was amazing. After buying and considering installing a '92 condensor fan, I opted instead for an aftermarket unit, one of the readily available pancake fans. Much easire to install since the 83 did not have all the holes etc. I ran a hot lead from the fender well terminal block to a relay. Radiator on this car had already been replaced and had a temp sensor mounted in it--unused. Originally I had planned on wiring the hot lead of the relay coil to the OD solenoid. That way whenever fourth was in, the fan would not work. However, since the default for the OD solenoid is "energized", that is, fourth available, that won't work. The OD solenoid is energized even at idle, when the fan is really needed, so it cannot be switched through the OD solenoid. I'm currently working through the schematics to see if there is a speed signal I might tap, but so far I've found nothing. Thus, for the moment, the hot signal to the relay comes from the compressor clutch circuit, through the temp switch, to the fan. Relay ground leg is just grounded. I was going to run the hot from the clutch, and the ground through the temp switch, but that seemed extreme.

Check out mattsonsradiator.com Of course you can get Hayden fans just about anyplace as well, P-Boys etc.

Good luck. If you come up with an answer to the OD issue, I'd love to hear it!

DS

My two-relay fan solution.

Pardon me, but I think I may have misunderstood something and responded too hastily in my earlier post. I’ll try again to explain what I have in mind with what I hope will be a little more clarity. This is what I have in mind for my '82 245 w/M46.



Here’s my idea for how to have the benefit of the add-on condenser fan available at low speeds when it is needed most and unavailable at high speeds when it is not needed at all: I think of this as a two-relay solution.

The first relay would be wired up as you have described, signal from the compressor coil and through the radiator thermostatic switch, 12 volts from the fender wiring block, fan (load) assigned to terminal 87 on a “normally open” type relay. [I imagine a normally open relay would work like this: when there is no signal voltage (from the compressor), or no ground (through the radiator thermo switch), the circuit is “open” and no voltage is delivered to the load (your new fan).]

The second relay in my two-relay solution would be in addition to all of the above. This second relay would be the five-pin type with two “load” terminals: terminal 87, as above, “normally open,” and a terminal 87a “normally closed.” This second relay could be wired into the signal circuit of the first relay anywhere between your compressor, thermo switch, and ground. The signal circuit of the first relay becomes the load of the second relay (connected through the second relay at terminals 30 and 87a). As the second relay is “normally closed” (circuit “on”) to terminal 87a, the first relay will operate as normal as long as the second relay is not energized. It would be as if the second relay were not there.

But, when the second relay is energized, its terminal 87a would switch to “open” (circuit “off”), interrupting the signal circuit of the first relay, and the first relay (and your new fan) would be disabled. This second relay would get its signal voltage from the overdrive circuit, anywhere between the overdrive relay and the overdrive solenoid. You could tap into the circuit right near the relay (mine’s behind the dash next to the glove box). You could mount both relays together under the hood to make future fault tracing a little simpler. Terminal 87 on the second relay will be unused and should be carefully insulated.

Hope this helps. Let me know.

Steve.

Hi Steve. Delayed reply, but I've been out of town for a few days.

Yes, I thought through the two relay system pretty thoroughly as well. Aside from the extra complexity and having all the extra wiring, I want to actually sit and diagram it. However I'm in agreement, a second relay is required so that the ...shall we call it the power relay? for the fan is controlled by a second circuit for the OD fan cutout. The main reason I did not pursue this is because regardless of the "default on" position of the OD solenoid, there is also the issue that in regular driving, the bloody gearbox can actually upshift to OD 4th at a very low speed, or well below "highway" speeds. That is what really stopped me from pursuing it. Point being that I don't want the fan to cut out at 25, which is a speed that will regularly find the car in 4th. Up here our surface street speeds range as high as 60 (we are not very congested). However, if it's hot out, which it is at this time of the year, and the car was tooling along at 35 in 4th, I would still want the fan on (since it might be 105 outside). I want that fan running until the car hits, say, 50. In other words, unless the car is traveling at or near highway speed, I want the fan on. It occurs to me that what the second relay might need to trigger is is a sail switch or an ambient temp switch. Properly position (someplace, don't know exactly where) an ambient switch might be cooled enough by sufficient airflow to kick in the second relay, or just break the ground to the first one. A friend in electronics recommended a "track" sensor. This is conveyor technology. A proximity type switch that does not require a reflector which measures the speed at which a surface is passing. That type of switch could literally point at the roadway and measure velocity. Another possibility is a driveshaft sensor like the aftermarket cruise systems used to use. My goal is to find something that I can install right up front, near the relay I have right next to the mail terminal junction (by the battery) so that all my wiring is right there. By the way, I fused my circuit by installing another weather-tite fuseholder right next to the main system fuse on the "rail". I had the local trophy shot heat-emboss "FAN" on the plastic cover and "MAIN" on the other one. Do you remember Rover sedans? If so, you may recall "Icelert", the box on the front grill that measured reflectivity of the road service to warn of glare ice. The controls for this were mounted on the left of the dash. A rheostat and warning light. When I pulled my Rover engine and swapped to Nissan power I put in a big electric fan (for idling for hours crossing the border in Mexico). Though the fan had a temp sensor in the radiator,I used the wiring from the Icelert to put in a manual overide toggle switch in place of the dash rheostat. That way I could just turn on the fan when I wanted. I might just do that, though it's not the solution we are looking for of course.

I have my nephew, who works for a conveyor manufacturer in Switzerland, getting me some information on proximity sensors. I'll let you know what I find out. By all means do lets keep in touch as this is a neat project. This week's task is to finish fiddling with my new remote filter setup using the 740 Turbo thermostatic remote filter boss and additional 90 degree adaptor from Ford Racing (Ford parts....never thought I'd do that, but how apropos).

Dave

Thanks for your help with my fan plans. I guess I didn't think my way through the OD solenoid wiring. I haven't tried this out, but here's a thought: if the OD solenoid is (default) HOT, with the 4th-gear switch ("in gear") completing the circuit which energizes the solenoid (that is, 4th-gear switch completes to ground), couldn't we energize our fan relay at the 4th-gear switch using an 87a/b relay, using the normally open contacts?
Best of luck.