MACS Monthly Newsletter - 2017 - SEP7

Electronic Module Scanning / Resets Relearns
asTech Corporation

Companies are popping up that address the issue
of scanning and programming / resetting electronic
modules via factory OEM scan tools and remote interface devices that you connect to your customers'
DLC. (Fig. 13)
The bottom line is to always be training and thinking 'outside the box' in order to get the most cars
repaired with the greatest degree of accurate diagnostic in the least amount of time. A daunting goal
we live by daily but a worthy one none the less! ■

Figure 13: With the hardware's retail price of $2,500, this patented VCI
(Vehicle Communications Interface) allows master techs at asTech's diagnostic centers to use factory scan tools to access any module on the
vehicle at the same level a training factory technician can access. For
the shop who owns factory scan tools and is perfecting their technician's
diagnostic skill levels this might not be the answer. For some other shops
who simply need to stay in the game w/o making the investment in lots of
factory tools and training, this may be a viable alternative.

TRUCK HEATER CONTROL VALVES
MACS members work on many Class 8 trucks and
when temperatures begin to drop outside some of
their owners visit shops for heater-related repairs.
That's exactly what happened when the operator of
a 1992 Marmon 57S dropped his truck off at a member 's shop with a no heat complaint. For the technician, it was a pretty quick diagnosis too, considering that the temperature knob on the dashboard
wouldn't slide from cold to hot (without the risk
of breaking it). It also didn't take long to feel the
heater hoses and find warm coolant on one side of
the heater control valve, while the other side was
relatively cool. After disconnecting the cable, the
dash control moved freely, so he determined a replacement valve should do the trick.
That's not as easy as it sounds when dealing with
a truck this old. Most parts can still be found (especially with the help of some MACS distributor
members), but sometimes it takes trial and error
to get it right. In this case, the technician looked
through catalogs, matched up pictures, ordered a
replacement valve and installed it. Now the truck
has heat but the dash control is backwards; it puts
out heat when the knob is on cold!
Closer inspection of the valve showed why. This
type of valve is directional, meaning that when the
cable pulls up on the pin, water is allowed to flow;
however, when the cable pushes down, the flow
is cut off. See Figure 14. They needed to purchase
the opposite valve, which closes when the cable is
pulled up. It appears the manufacturer could have
set this valve up to be more universal if there was a
pin on the other side of the arm and a cable clamp
opposite the bolt, but that might not work in other
situations. Either way, replacement of this incorrect
valve is in order.

September 2017

Steve Schaeber

This is where details really matter because there
are a multitude of valve variations. Some valves are

Figure 14: This heater control valve is universal, but directional.

manually controlled, and the operator has to physically get out of the cab to open or close a valve (or
valves) in the engine compartment any time they
require heat. Others, such as this Marmon are cable operated, while still others are controlled by
vacuum or even electric motors. Then there's the
configuration of the valve itself which is dependent
on how it's mounted and where it's located under
the hood. You can get "T" valves, 90° valves, offset
valves where the inlet position is higher or lower
than the outlet (rather than being directly inline),
various sized ports (such as ¾" inlet and ⅝" outlet),
and even valves with differing degrees of cable-tovalve-orientation offset. These details seem small,
but are necessary to coordinate heater valve operation with the operator 's dashboard controls. ■

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017