Coolant fan override switch

[Leroy Eckert]

Thanks Ron:
When I started having creeping heat I could not figure it out. I changed the
Alarmstat and it stopped. Apparantly, the sensor did not fail totally but was
intermittant, causing the fan to act weird. After I changed it to the factory
value, 195 degrees, I did not like the average water temperature. So I ordered
a 190 degree and I like the results of it much better.
The problem is you cannot test the sensor while sitting still, and you cannot
hear the fan while driving. You can only see the result on the temperature guage
with the override off and the a/c off. It makes it difficult to troubleshoot.

Leroy Eckert
1990 WB-40"Smoke N Mirrors"
Niceville, FL





----- Original Message -----
From: ronmarabito2002
To: WanderlodgeForum@yahoogroups.com
Sent: Monday, February 19, 2007 7:46 PM
Subject: [WanderlodgeForum] Re: Coolant fan override switch


I have not had a alarmstat failure on my 92, but I did on my 83PT40.
It definitely failed into high speed fan mode.

R.E. (Ron) Marabito, Dallas, TX 92WB40

--- In WanderlodgeForum@yahoogroups.com, "Leroy Eckert"
wrote:
>
>
>
> This is exactly how my system works. I would think yours is similar.
> 1.With the fan override off and chassis a/c off the fan will spool
between approx 400x600 RPM. This continues until the temperature
reaches 195 degrees, (190 degrees now in my coach) then an alarmstat
turns the fan to high speed approx. 1800 RPM. The alarmstat operates
in an 8 to10 degree range, therefore cycling the fan from idle to
high mode over and over again, hence the cycling you may see on the
engine water temperature gauge. ( you will not see the cycling with
the chassis a/c on.) you may not see cycling in this configuration in
hot temperatures or while climbing hills.
>
> 2. Fan override off, and chassis a/c on: When the chassis a/c
switch is turned on( either pilot or co-pilot) the fan goes into high
mode, stays in high mode until the a/c switch is turned off. This
takes the fan override and the alarmstat out of the system, and
provides additional continuous cooling air for the condenser. My
condenser covers the top half of the radiator. Earlier models a/c
condenser are on the roof, cooled by electric fans.
>
> 3. Fan override on, chassis a/c off. Operates the same as item 2.
except the fan override switch has now taken the Alarmstat out of the
system. Using this switch in winter in my coach holds the engine
water temperature at engine thermostat value approx. 170-175. I
expect to see continuous 190 or less in summer in this configuration.
>
> 4. When my alarmstat failed/or became intermittent I experienced
creeping heat. I'm told that alarmstat failure is suppose to default
to fan high mode. I have not verified that.
>
> 4. So you see, Bluebirds engineers forced our coaches to run on the
high side of the DD specified range ( 170-210max, alarmed at 215
degrees: Ref: 13.12 DD Service Manual Pg. 13-48) by specifying the
195 degree alarmstat. Presumably, the thinking is that high fan RPM
robs power so the higher you run the temperature the less fan
activity. Unfortunately, that simply isn't the case because once the
195 degree temperature is attained the fan cycles continuously anyway.
It does the same thing in my bus using a 190 degree alarmstat ,
however, the benefit of the lower water temperature is lower engine
oil, tranny and retarder temperatures.
>
> When it gets hot, I intend to use my VMSpc to evaluate the
temperature differences resulting from my alarmstat value change from
195 degree to 190 degree. I fully expect to see a 6-8 percent
reduction in drivetrain component temperatures.
>
> The foregoing post has been documented with temperature values,
estimated outside air temps and road conditions while driving my 1990
WB-40 over the past 5 months.
>
> Leroy Eckert
> 1990 WB-40
> "Smoke N Mirrors"
>
>
>
>
>
>
> ----- Original Message -----
> From: David Brady
> To: WanderlodgeForum@yahoogroups.com
> Sent: Sunday, February 18, 2007 10:36 PM
> Subject: [WanderlodgeForum] Coolant fan override switch
>
>
> Folks,
>
> On my '02 LXi, with the engine at idle, the fan seems to rotate
> at 400 rpm or so (give or take, lol), when I enable the override
> switch there doesn't seem to be any change in fan speed. Should
> there be? or are there other parameters at work hear; i.e., engine
> temp, etc. What are the common failure modes of the fan override?
>
> Thanks,
> David Brady
> '02 LXi, Smokey
> NC
>
>
>
>
> [Non-text portions of this message have been removed]
>





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