No Heat!!!

[danny2008]

I have a 1997 Pontiac Transport...when the heater is on in any position at the blowing level of one it is slightyly warm and when changed to a higher blowing level it is cold, there is absolutely no heat now what can i check/do to fix this problem?? Also having a cylinder 1 mis fire any suggestions??
Daniel

[LMP]

THere are a few possible explanations, the most favourable would be clogged heater core or failed diverter flap motor (accessible under dash)
.
However, this is also a symptom typical of a common failure of the 3.4 engine and this possibility cannot be ignored: blown head gasket. (exhaust invades the cooling system and stops coolant flow to heater core).
Are there any signs of engine over heating, temperature needle fluctuations, loss of coolant (having to top off the coolant tank regularly), steaming? CHeck fluid level in radiator. Any one on these additional signs must be taken seriously. This forum - as well as Lumina van, venture, Montana and other GM - have a hefty collection of similar cases.

[Headnsouth]

Your thermostat maybe stuck open also. What does the temp guage show?

[bighank]

Originally Posted by LMP

THere are a few possible explanations, the most favourable would be clogged heater core or failed diverter flap motor (accessible under dash)
.
However, this is also a symptom typical of a common failure of the 3.4 engine and this possibility cannot be ignored: blown head gasket. (exhaust invades the cooling system and stops coolant flow to heater core).
Are there any signs of engine over heating, temperature needle fluctuations, loss of coolant (having to top off the coolant tank regularly), steaming? CHeck fluid level in radiator. Any one on these additional signs must be taken seriously. This forum - as well as Lumina van, venture, Montana and other GM - have a hefty collection of similar cases.

How do you get to the diverter motor? Had no heat for 3 months then it suddenly changed to all heat. What do I remove and what do I replace?

[LMP]

THIs is under the dash...so probably you would have to remove some sections of the instrument panel lower fairings. THe diverter flap is electrically driven by a geared motor and the gear is known to have failed at times.

THe diverter flap decides if the incoming air goes through or around the heater core.