Date: Wed, 12 Sep 2007 09:06:35 -0700
Reply-To: Mark Drillock <drillock@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Drillock <drillock@EARTHLINK.NET>
Subject: Re: A/C and High Radiator Fan Questions
In-Reply-To: <BAY125-DAV133DA92FBAA69BC8F14481A0C20@phx.gbl>
Content-Type: text/plain; charset=us-ascii; format=flowed
I'm afraid you are mistaken on a few points. There is no signal from the
A/C system to trigger the highest speed radiator fan relay circuit, only
the other way around, to turn off the compressor when radiator temps are
too high. The only way the A/C triggers highest speed is indirectly, by
triggering the radiator temp switch due to added cooling system load
imposed by the A/C.
The lowest fan speed is turned on by either the lower temp switch on the
radiator or by the A/C relay when the A/C is on.
The relay in the main fuse box is connected only to the refrigerant high
pressure switch in one of the A/C hoses and runs medium fan speed when
pressure is high. (on 2wd models without A/C this is the high speed fan
relay)
As for the windings of the resistor, BOTH are used in series during low
speed fan operation and one alone for medium speed.
Not that too many people care, but there are some wiring errors in both
the Bentley and Mitchell diagrams for 86-91 A/C systems. There are 3
errors that are easily encountered by even home mechanics, since they
have to do with the radiator fan temp switch wiring and the radiator fan
resistor wiring, both of which are common to need servicing.
1. wire from fuse panel pin C7 to rad temp switch pin 3 should be
red/white (not black)
2. wire from rad temp switch pin 2 to fan resistor pin 2 should be
red/black (not red/white)
3. wire from fuse panel pin H3 to fan resistor pin 1 (3 on Mitchell)
should be black (not red/black)
4. ground wires for 2nd and 3rd stage relays incorrectly shown as
independent and very wrong ground point given for 3rd stage relay. Both
are in fact tied together and grounded at main dash ground crown. Relay
ground wire size also shown wrong, should be .5, not 2.5 or 1.5
I have verified the above on all 5 of the A/C radiator fan harnesses
easily accessed in my garage from scrapped vans 86-90 with factory air.
Mark
Dennis Haynes wrote:
> Both the AC and the radiator can put the fan in the super duper high
> speed. If the radiator switch does it, then the compressor gets cut off.
> The windings on the resistor are one for radiator low speed which is now
> fed from the relay on the fuse box and the other is for the lowest speed
> for normal AC operation.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Mark Drillock
> Sent: Monday, September 10, 2007 9:10 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: A/C and High Radiator Fan Questions
>
> An 87 with factory air has a 3 speed fan, not a 2. What you are calling
> high speed may well be medium speed.
>
> High speed is only turned on by the radiator temp switch when high
> radiator temps are sensed.
> Medium speed is only turned on by the A/C system when the pressure in
> the hose gets too high.
> Low speed is controlled by 2 things, either the radiator temp switch
> lower section or the A/C relay when the A/C is on.
>
> There is a relay for high speed, another relay for medium speed, and the
> low speed is powered directly.
>
> If you remove the medium speed relay and the fan still runs at what you
> think is high, you must be right. If not, then you are really hearing
> medium speed. The high speed relay is hidden and hard to reach while the
> medium speed relay is right there in the main relay panel where you can
> pull it in 2 seconds. Page 97.102 of the Bentley shows the middle speed
> relay, speed 2, is in position 5.
>
> Mark
>
>
> Tom Salicos wrote:
>
>>I have the A/C running after a couple of summers w/o. Subie yes, but
>
> the
>
>>van has always done this. The high fan speed comes on when it shouldn't
>
> be
>
>>required (as far as I understand).
>>
>>Sunday it was parked for about two hours on an 85 deg. Day. When I
>
> started
>
>>it the high rad fan came on immediately and stayed on for at least ten
>>minutes as I drove home. Came on and off a few times. The temp guage
>>didn't show the H20 temp even to half way to the LED.
>>
>>Turn the A/C off and the hi fan stops.
>>
>>Other times it has just come on at high speed, even though it was no way
>>near hot. Stays on for a minute then shuts off.
>>
>>W/O the A/C the high speed fan never has to operate due to high temps.
>>
>>So, what controls the high speed fan when the A/C is on?
>>
>>Thanks for any tips.
>>
>>Tom Salicos
>>'87 Syncro Westy EG-33
>>
>
>
>
