ablose58

Hello all! I am going to ask a relatively dumb question only because I haven't received my manuals yet, they are on order from 928 intl. So do I understand that when you have the a/c on the aux fan should be on as well? If so where would I look for this trigger or current flow? I am forever greatful!!! AL oh it is an 84s model 4.7l auto.

ROG100

I know that on my 82 the fan does not come on with the A/C.
However on my 89 & 93 it does.
Somewhere in between the change was made.
My guess is that the 84 does not.
Hope someone else will confirm.

WallyP

The change on the A/C activation of the aux cooling fan was made in '87. Prior to '87, the fan is triggered by a refrigerant temp switch, mounted on the stem on the receiver/dryer. This doesn't work too well...

On the '87 and up cars, the fans are triggered by a refrigerant pressure switch, which makes the fans come on as soon as the A/C compressor comes on. This works much better.

For the early cars, one possibility would be to add a relay to the A/C compressor power wire. This would have two benefits:
- Removes the load from the (undersized) relay in the HVAC control head, making it live much longer.
- By adding a diode and another wire, you could power the aux fan from the relay, so that the fan automatically runs anytime that the compressor is on. This will give better A/C performance, and will help engine cooling when the A/C is used.

ROG100

Wally,
I would love to do that modification on my OB's.
Could you please give a little more detail on how to accomplish the task.

Do I tap a relay circuit into the A/C compressor power wire and from that relay energise the fan circuit.
Electrics are not my strong point.

docmirror

The best way would be to take a tap from the AC control button in the dash. Since the AC compressor cycles on and off, the fan would also cycle at the same rate. This makes for some stress on the electrical system to pull these two motors at the same time.

Locate the line from the AC button, to the small relay in the climate control module. Take a tap from that to energize the relay, then tap the 12V from the aux fan to provide the main power to run the fan. Just route it through the relay contacts, and insure there is a solid ground on the aux fan. I can come by later and hook it up for you?

Doc

WallyP

Here's how I would do it:
- Get a heavy-duty single-pole single-throw normally-open 12 vdc relay with the contacts rated for thirty amps.
- Get a good-quality inline fuse holder, a few feet of 16 gage stranded automotive wire, and a few feet of 12 gage stranded automotive wire. You will also need a few terminals, to fit the situation.
- Disconnect the battery ground strap and insulate it so that there is no possibility whatsoever of the strap touching ground.
- Find a spot on in the right front corenr of the engine compartment to safely attach the relay. If it is not bolted to grounded metal, you will need to install a 16 gage wire from the relay to a good chassis or engine ground point.
- Make a wire harness from 12 gage wire: Ring terminal to fit under the sump start terminal, a very close in-line fuse holder with a 30 Amp fuse, enough wire to reach the power terminal of the relay, and a suitable terminal to hook to the relay.
- Make a wire harness from 12 gage wire to go from the output terminal on the relay to the fan. Leave the existing fan power connection in place, and add the new power lead to it.
- Make a harness from 12 gage wire to run from the same output terminal of the relay to the connector on the compressor.
- Disconnect the power lead from the A/C compressor and attach it to the trigger terminal of the relay. Use 16 gage wire if you need to extend it.

This should turn the fan on anytime that the compressor is running, without screwing up the normal fan functions.

ablose58

Thanlks all Much appreciated !! I wasn't sure about it ,now it is crystal clear!!!!! AL

ROG100

Wally and "The Doc"
Thanks for the info.
It is now high on my To Do list.
Roger