Fluctuating heater with engine load

[richard guthart]

When driving in the mountains the air from my AC vents was sometimes very cold
and sometimes just cool. Turned out that hot coolant was sometimes flowing
through the heater core even with the dash controls set to AC. The vac-operated
valve was working..........didn't occur to me that when climbing a steep grade
the engine vac wasn't sufficient to keep the valve closed.

Now I have installed the manual shut-off valve in line with the vac-operated
one, and will run in the summertime with that closed. The valve was mentioned in
a previous post - NAPA BK 660-1140.

Richard

>
> |In fact when traveling in the mountains, when vacuum
> |dropped below 4, the outside heater vents would open even though the AC
> |was on. Then when vacuum got back up to 6, they would close. I need to
> |figure out how to correct that problem. Justin
>
>
> Gene's recommendation of the brake booster vac pump is also a good idea.
>
> Mark
>

 

[bartz paul]

Scott:

I've had a ball valve in the heater coolant line for three years. I've
found there have been a few times that I wanted heat while driving down the
road and either did without or stopped to turn it on. Would be nice to
control via vacuum.

Paul Bartz

From: Adohen [mailto:Adohen]
Sent: Wednesday, August 18, 1999 3:07 PM
Subject: Re: GMC: Fluctuating heater with engine load

In a message dated 8/18/99 2:53:43 PM Eastern Daylight Time,

The vac-operated valve was working..........didn't occur to me that
when climbing a steep grade the engine vac wasn't sufficient to keep the
valve closed.

Why not just put ball type valves in the heater core lines seen in the
engine compartment? Close in summer, open in winter or when you are cold.
Anybody do this, pro or con? Maybe I'm just not familar enough yet with
what has been discussed about this topic.

 

[richard guthart]

Scott,

The NAPA # BK 660-1140 is such a ball valve. I put one in the line to the heater
core, locating it under the A/C receiver-dryer. That way I can reach in through
the grill to open it if I think I might want heat.

Richard

> In a message dated 8/18/99 2:53:43 PM Eastern Daylight Time,

>
> > The vac-operated
> > valve was working..........didn't occur to me that when climbing a steep
> > grade
> > the engine vac wasn't sufficient to keep the valve closed.
>
> Hey Gmcers!
>
> Why not just put ball type valves in the heater core lines seen in the engine
> compartment? Close in summer, open in winter or when you are cold. Anybody
> do this, pro or con? Maybe I'm just not familar enough yet with what has
> been discussed about this topic.
>
> Scott NEHODA'S BACK
> YARD
>

 

[jim bounds1]

Paul,
Gotta tell you a run in I had with the dumpster. 2 weeks ago I drove with
4 kids and an adult 1500 miles to the Appalatchian trail for a weeks
backpack. The trip was great & the coach drive like a spaceship but the
dash air almost killed me!!!

I got hot air from the dash vents & cool air from the lower plenum (76
coach, type II unit). I got sooooo much air from the fire wall openings
that we all were sweating masses.

Solution: I am going to rip the entire dash air system out (anyone need
one). I'm going to add 2 secondary cooling systems overhead hooked to the
compressor. I will have cool air in Florida!!!

That heat control valve failed, I vise gripped off the hose on both sides
and did no good, I am over that dash air!! This coach is fooling with the
wrong wrench twister!!

I'll let you know what pans out.

See ya,

Jim Bounds

P.S. No. I haven't had time to fool with the cruise system but I will soon!
- ---------------------

>In a message dated 8/18/99 2:53:43 PM Eastern Daylight Time,

>
>> The vac-operated
>> valve was working..........didn't occur to me that when climbing a steep
>> grade
>> the engine vac wasn't sufficient to keep the valve closed.
>
>Hey Gmcers!
>
>Why not just put ball type valves in the heater core lines seen in the
engine
>compartment? Close in summer, open in winter or when you are cold. Anybody
>do this, pro or con? Maybe I'm just not familar enough yet with what has
>been discussed about this topic.
>
>Scott NEHODA'S
BACK
>YARD
>
>
Jim Bounds/Co-op Motor Works Orlando www.gmccoop.com