Adding 3 fans to rear A/C condenser

[dralph12]

HELP!! Power from the rear fues box?
I looking for how to wirie the relay and power for the fan. can anyone provide a diagram of how they did it ?
or a point to point wiring direction.

[mthomas58]

Originally posted by dralph12
HELP!! Power from the rear fues box?
I looking for how to wirie the relay and power for the fan. can anyone provide a diagram of how they did it ?
or a point to point wiring direction.

I had a helluva time getting the relay wired properly....lots of trial and error. I'll take a look at the wiring tomorrow and post a diagram.

[mthomas58]

Originally posted by dralph12
HELP!! Power from the rear fues box?
I looking for how to wirie the relay and power for the fan. can anyone provide a diagram of how they did it ?
or a point to point wiring direction.

I have been meaning to diagram the relay wiring for my records since it was such a cluster getting it wired up. Had help from a neighbor and father-in-law on the phone (engineer) to consult. In the end, I wasn't clear on what we had actually done! Anyway, here is how we wired the fans. Hope this helps. Once I get everything finished (may add one more fan and swap out relay for a time delay model) I'll clean up the wiring with some shrink tubing and wire ties.




Blue power lead from fans directly to fuse block. Red wire from Relay pin 30 to fan ground wire. Orange wire from Relay pin 86 to A/C power lead (triggers relay only - does not power the fans). Center pin is 87a and is unused:



Orange wire from relay pin 30 connected to green A/C power lead via snap-on wire tap/splice

[nyne11]

I have 2 Fans mounted as per picture. am I to understand this is not a factorystandard addition?

[rnln]

dralph12,

The way mthomas58 installed it looks diff from what I did. I am not sure which way is better or they are the same but my fan always get (-), relay supplies the (+). The below method I got from gathering info on this board on how to use relay.

85 to ground (car chassis).
30 to batery (+) terminal.
86 is the turn-on-signal wire (+). Can be connected to a switch or any source. In this case should be the AC compressor?
87 supplies (+) to fan (+).
Fan ground is to engine lid.
87a no use.

[dralph12]

Thank You!!
I will get mine wired up in a few weeks and post my Pic's.
I am replacing the rear deck lid condenser. I found a guy that manufacturers condensers.
My OEM condenser has 8 rows of tubing, his will have 12 rows of tubing in the same
space " smaller tubing = more surface cooling area" I will post these pic's soon.

[mthomas58]

Originally posted by dralph12
Thank You!!
I will get mine wired up in a few weeks and post my Pic's.
I am replacing the rear deck lid condenser. I found a guy that manufacturers condensers.
My OEM condenser has 8 rows of tubing, his will have 12 rows of tubing in the same
space " smaller tubing = more surface cooling area" I will post these pic's soon.

Dralph12, check out Mysterytrain's post here.....this is a better way to wire the fans. I'm going to rewire mine accordingly.

Rear A/C condenser fan relay wiring diagram

[911pcars]

Here's a generic schematic of a 1M-1B relay, Bosch-made or otherwise. The terminal numbers are DIN spec, meaning all DIN-spec !M-!B relays adhere to this terminal ID standard.

Typically, there are two circuits; the power circuit (terminals 30 and 87) and the control circuit (terminals 86 and 85).



Terminal 30 connects to source voltage (from the battery or equivalent). 87 leads to the load (condenser fan motor).

Terminal 86 connects to a switched source circuit to chassis ground via 85. When the control circuit switch closes, current flows through the relay coil which causes the contacts to close and complete the 30/87 circuit.

The 87a terminal is there in case a circuit designer wishes to use the control circuit to open the normally closed circuit through 30/87a.

While any relay can be located on either side of the load (fan motor), it's more Japanese-style to place the power side of the relay (30 -> 87 circuit) on the ground side of the load. The theory is that voltage is reduced on the ground side of the load thus less wear on the relay contacts.

Japanese style:
Bat. -------fuse--------> fan motor------>30 relay 87 ---> ground.

DIN-style:
Bat. -------fuse--------> 30 relay 87 ---> fan motor------>ground.

Sherwood

[dralph12]

Ok I wired up my rear A/C condenser fan, but havent done the time delay relay yet.
Here is my issue! fan works great and my AC is under 50 Deg. at the vent but when the AC and Fan are on there seems
to be to much of a load on the alternater. My Tachometer goes nuts and the other gauges start bouncing around.
In fact I know the load is to much becouse I took the car out for a nice drive with the AC on and I needed to charge the battery when I got home. I have been having this issue before I added this fan. It started when I added the first fan to the Oil cooler. I know when the battery needed to be recharged that both fans were on "AC and Oil cooler" I hAVE CHANGED THE ALTERNATER and the Battery but
Im still having the problem. this happend only then one of the added fans are on. Any idead? HELP!!

[mthomas58]

Third fan finally installed today!

[911pcars]

Is there an advantage in using three fans vs. two of the large ones? Current load vs CFM air flow?

Sherwood

[Early_S_Man]

Sure would be interesting to see some data acquision runs on alternator heat sink temps, head temps, cylinder temps, oil temp at scavenge line outlet port ... before and after the install of such large restrictions to the air flow into the engine fan??? My estimate is that you could raise oil temp 10°F - 20°F with such an install. Maybe a cool collar to offset the increase?

[mthomas58]

Originally posted by 911pcars
Is there an advantage in using three fans vs. two of the large ones? Current load vs CFM air flow?

Sherwood

I was limited on fan size due to my choice of mounting pullers under the condenser with clearance restrictions on heater duct and alternater fan housing. I did have to eliminate the airbox horn also.

Larger pusher fans above the condenser would move more air, however, some cutting of the tail louvers may be required and I did not want to do any cutting of sheet metal.

[911pcars]

Originally posted by mthomas58
I was limited on fan size due to my choice of mounting pullers under the condenser with clearance restrictions on heater duct and alternater fan housing. I did have to eliminate the airbox horn also.

Larger pusher fans above the condenser would move more air, however, some cutting of the tail louvers may be required and I did not want to do any cutting of sheet metal.

Mark,
Okay. I understand your situation.

If pusher fans are more efficient, is it possible to lower the mounting point of the condenser, then install pusher fans above? In other words, just swap the location of fans and condenser.

MHO, I don't think the add'l fans block significant air volume. The engine cooling fan is going to get air from whatever air source/opening and push it into the engine. IOW, no engine compartment vacuum is anticipated.

With the A/C OFF and aux. fan(s) ON, the engine should receive more ambient air at idle and low speed.

Sherwood

[mthomas58]

Originally posted by 911pcars
Mark,

If pusher fans are more efficient, is it possible to lower the mounting point of the condenser, then install pusher fans above? In other words, just swap the location of fans and condenser.

MHO, I don't think the add'l fans block significant air volume. The engine cooling fan is going to get air from whatever air source/opening and push it into the engine. IOW, no engine compartment vacuum is anticipated.

With the A/C OFF and aux. fan(s) ON, the engine should receive more ambient air at idle and low speed.

Sherwood

Sherwood, Pullers are more efficient than Pushers, but larger pushers could be mounted above the condenser (probably two 10" fans) that would move considerably more air. I thought about dropping the condenser down a little with some spacers, but I've got a rear wiper and the motor assembly would not allow.

I agree with you....condenser fans blocking of air through the grill not material (just my opinion).

Thanks!

[AlfonsoR]

Nice AC thread

[echecsqueen]

Resurrecting this old thread to say thanks for all the info. Adding fans to my granite green ‘88 today. It can’t hurt!

[Ryxx]

Has anyone considered 2 10inch fans, one pushing and one pulling?