Heater Motor Swap
The Chevy Blazer heater motor upgrade for Jeep CJs and Wranglers
has been bouncing around the Net for as long as I can remember. It is
remarkably easy and it greatly increases the air flow through the
heating system. When my heater core began leaking like a sieve, I
figured it was a good time to do the upgrade.
This upgrade works for '78-'86 CJs as well as '87-'90 Wranglers.
Some of the CJs built in 1977 used the old style heater housing with
the heater motor behind the dash. I haven't heard of anyone doing this
upgrade with the old style heater housing or with a Wrangler built
after 1990. Any 1977 CJ with a heater motor sticking out of the fire
wall will be able to do this upgrade.
Since I was able to buy the motor brand new at my local auto parts
store for only $22, I decided not to search the junk yards for a used
one. It takes a fair amount of time to install the motor, so I didn't
want to install one on its last legs or waste a couple of hours at the
local u-pull-it to save $17.
If you go to your local discount auto parts store, it is best not
to confuse them with the truth. Ask them for a heater motor for a '73
Chevy Blazer with a 350 and air conditioning. The part is the same for
all Blazers of that year regardless of engine size or air
conditioning, but this is the normal stream of questions. The key
thing may be to get the motor that does not include "heavy duty" or
"backseat heating". According to Jeff, the part number for Siemans
#PM102 is the one that fits the fan wheel correctly. This cross
references to the Four Seasons part number 35587.
If you go to the junk yard for a motor, the heater motor you are
looking for was used over several years in several different models. I
don't have a complete part cross reference, but any motor out of a
Chevy pickup, GM pickup, Blazer, or Jimmy should work from '71 to '76.
The motor may have the part number "1312" on it.
The only thing tricky about doing the upgrade is you will have to
enlarge the opening in the fire wall to 3 1/4" to accommodate the
larger diameter motor. A air cut-off wheel, drill with a hole saw,
saber saw, or hack saw could be used to do the job. Other than that,
the tools in most peoples tool box and anyone capable of changing
their oil should be able to do the upgrade.