Netters--
You might recall my post of about a week ago where I mentioned that
while performing the fan clutch diagnosis procedures described in the X
- -7525A Maintenance Manual, the air conditioning system experienced a
"blow out" where by I lost all of the R-12 refrigerant. Well, I got my
Transmode back from the repair shop today and the $500 bill makes me
wish I had not followed the instructions in the manual. The procedure
that got me into trouble is found on page 6K-9, paragraph d., where it
reads:
"With thermometer in position, cover radiator grille sufficiently
to induce a high engine temperature. Start engine and turn on A/C
if equipped, operated at 2,000 rpm."
This is no unintentional mistake in shop manual, because in paragraph f.
on the same page the procedures call for turning off the A/C after
performing the diagnostic to aid in engine cooling.
The object of the procedure is to cause the engine to heat up the
radiator and engine coolant so that the temperature when the fan clutch
engages can be observed. However, the A/C mechanic told me that
blocking the flow of air through the grille also blocks the flow of air
through the A/C condenser coils and resulted in very high head pressures
in the compressor and hoses which caused the blowout. He said that
because of this result, one should never block the flow of air while the
A/C is running. In fact, he has some large floor fans that he will
position in front of vehicles he's working on to help keep the condenser
cool when operating the A/C during service procedures to the A/C system
on hot days. This is a safety precaution more than anything because no
one wants to be in the path of high pressure freon spewing out of a
broken fitting.
So, I guess I learned a valuable but expensive lesson with my attempt to
diagnose my fan clutch per the shop manual instructions. I hope that no
one reading this tale of woe learns the same lesson the way I did.
Phil Stewart
'76 Transmode, TN
You might recall my post of about a week ago where I mentioned that
while performing the fan clutch diagnosis procedures described in the X
- -7525A Maintenance Manual, the air conditioning system experienced a
"blow out" where by I lost all of the R-12 refrigerant. Well, I got my
Transmode back from the repair shop today and the $500 bill makes me
wish I had not followed the instructions in the manual. The procedure
that got me into trouble is found on page 6K-9, paragraph d., where it
reads:
"With thermometer in position, cover radiator grille sufficiently
to induce a high engine temperature. Start engine and turn on A/C
if equipped, operated at 2,000 rpm."
This is no unintentional mistake in shop manual, because in paragraph f.
on the same page the procedures call for turning off the A/C after
performing the diagnostic to aid in engine cooling.
The object of the procedure is to cause the engine to heat up the
radiator and engine coolant so that the temperature when the fan clutch
engages can be observed. However, the A/C mechanic told me that
blocking the flow of air through the grille also blocks the flow of air
through the A/C condenser coils and resulted in very high head pressures
in the compressor and hoses which caused the blowout. He said that
because of this result, one should never block the flow of air while the
A/C is running. In fact, he has some large floor fans that he will
position in front of vehicles he's working on to help keep the condenser
cool when operating the A/C during service procedures to the A/C system
on hot days. This is a safety precaution more than anything because no
one wants to be in the path of high pressure freon spewing out of a
broken fitting.
So, I guess I learned a valuable but expensive lesson with my attempt to
diagnose my fan clutch per the shop manual instructions. I hope that no
one reading this tale of woe learns the same lesson the way I did.
Phil Stewart
'76 Transmode, TN
