1998 Transport - NO HEAT!

Sounds like the ducting isn't connected to the ducts and all your air is being lost up under the dash.

I don't recall ever reading a similar complaint about a similar vehicle. Therefore the problem is probably specific to your vehicle only. I would look for doors and/or door motors not working, rusted up blower motor bearings, bad switch, bad high-speed relay, ductwork off (like FBR said), etc.

Does the AC work??

One VERY common problem with these vehicles is a leaky AC evaporator. If they leak, refrigerant oil coats the exchanger, and that holds dust, blocking air flow significantly.

Agreed, or a vacuum problem. Also note, no one would know if the evap was plugged without physically removing it to see. The STRANGest case I have seen with a similar complaint was that someone else had already replaced the fan motor with one from a cheap discount auto parts store, and the squirrel cage (fan blades) faced the wrong direction......Lots of spinning, not much air flow. GW

A/C - Poor Heat at Low RPM When Cold

File In Section: 01 - HVAC

Bulletin No.: 00-01-38-011B

Date: April, 2002

TECHNICAL

Subject: Poor Heat with Cold Outside Temperatures at Low Engine RPM (Install Auxiliary Coolant Pump)

Models:

1997-1999 Chevrolet Venture 1997-1999 Oldsmobile Silhouette 1997-1999 Pontiac Trans Sport 1999 Pontiac Montana

Attention: Implementation of this Service Bulletin by "GM of Canada" dealers requires prior District Service Manager approval.

This bulletin is being revised to correct the diagnostic information under the Correction section. Please discard Corporate Bulletin Number

00-01-38-011A (Section 01 - HVAC).

Condition

Some customers may comment on poor heat in the vehicle passenger compartment at low engine RPM. This condition is most prevalent at outside temperatures below 0°C (32°F).

Cause

The vehicle's heater core may not have sufficient engine coolant flow while the vehicle is idling. Anytime the engine RPM drops to idle speed, the temperature of the heated air may decrease to an unacceptable level even if the engine is already at full operating temperature.

Correction

A service only kit has been released which contains an electric auxiliary coolant pump. The components of this kit will boost coolant flow through the heater core whenever the outside air temperature falls below 0°C (32°F). The service kit is similar in design to the factory installed models on the 2000 model year vehicles. Any 1997-1999 vehicle that comes into the dealership that has not had the auxiliary coolant pump service kit installed and has an insufficient heating condition may need to have a pump kit installed.

Any 1997-1999 vehicle that comes >

The vent temp. on my van is around 140 F when its -20 outside going down the highway. Which is pretty good from checking other cars on the road now a days. The dealers "fix" was to remove those cabin air filters for the heater box intake. They said by not using any it improves air flow. I don't know maybe some fuzz or something over the years now has plugged it up more by not using filters. But I can't see any big issues not using filters anymore. There is millions of cars on the road with out heater box air filters!

I just can't believe they would manufacture a Van with such piss poor air flow. In the summer when really hot it has the same problem trying to cool. So your sitting there again with the stupid noisey fan on high roaring away!

Years ago I was at the parts department and mentioned my troubles. The GM parts manager heard me talking in his office and told me to come in. He had the same van and had the same complaint also. He was going after GM some how claiming it was a safety issue because it couldn't keep the front window free of frost. I never heard anymore about it though.