I am more familiar with 240's than with 740's. So that is my frame of reference for this question. The heated air mechanism for a 240 is problematic, in that more often than not, the thermostat inside the air cleaner sticks with the cool air blocked off and the hot air from the exhaust pipes diverted into the intake system. That situation has been the death of way too many AMM's. So most of us 240 owners, especially those living where the winters are not all that severe, simply disable the mechanism which closes off the cool air, thereby getting rid of the problem.

It appears the 740 has a similar heated air arrangement, though it is not as straightforward as that of the 740. Is the 740 heated air system as prone to problems as that of the 240? If so, how does one get at the thermostat mechanism to disable it? It seems to be located inside a bit of molded plastic that might not be so easy to get into? Thanks for the help. Allen H

I think they all fail. The flap on the 740 can be permanently set to cold. But, to do that you have to remove the assembly, remove the air temp thermostat, and then set the flap. In my case I screwed the flap to the housing to hold it open. Just a simple sheet metal screw.
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86 740T/87 745GLE/96 960 Wagon

Hi Allen;

I have the '89 745. At first I simply disconnected the heater tube where it connects into the air cleaner assembly. Later I took the pipe right out.

I've heard of some folks on this board failing the emissions test because this pipe was removed ... something to consider if you have to do this.

This is the remedy I've read most people do.
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Norm Cook Vancouver BC; 1989 745T 200,000KM