Car Repair > 98 chevy blazer >

Ask Your Car Question. Car Experts Answer You ASAP.

(Not a Car Question?)

98 chevy blazer 4.3 no heat to floor. Heat every vent but the floor. opened the glove box and the orange vaccum hose is not working, what cantrols the this?

Customer (name blocked for privacy)

Status: Closed Value: $5

A vacuum line .. usually plastic comes from the engine. Usually attached to a manifold vacuum source or near the brake booster vacuum. This line generally goes to a vacuum canister (or reservoir) and from there through the firewall to the heater controls. The heater control head then distributes the vacuum to control diaphrams
from there. The problem is usually at the source
of the vacuum . either the line has broken or been inadvertantly disconnected. The next spot is the canister which can break, corrode or generally leak. If you have good vacuum on the feed line on the passenger compartment side of the firewall,, check the control head for proper attachment of the vac lines and possible control head leakage.

Good Luck

Md4cars

Reply to Pat Melli's Post: I have vacuum from the maaifold, and to the black line of the control head, but just the orange line is dead? Is there a control vavle, why will only the defroster vent and the front vent blow heat?

I also took a black vacuum line from a diaphram next to the where the orange line is connected and connected it to the diaphram, it started to move in and out, but no heat to the floor?

The control head is on the dashboard? I also checked for fuction of this and I think it is ok? Should I look into replacing the control switch on the dashboard?

There's are several doors and or diaphrams. The one your looking at may be for the recirculation door or blend door , not necessarily mode doors.
The controlhead is the piece that contains the sliders (or buttons) for temp and mode and fan.
If you pull it out (requires some trim removal)
you will note a cluster of vac lines on the back
Check it doesn't leak and verify it is attached.
Next (with the car running for vac) switch the temp and mode settings and watch for a response from the various control diaphrams. (follow the vac lines if need be to see where they go) Generally there will be some actuators under the dash (center floor area) you will have to lower any trim panels to see. Inspect for vac lines not attached or otherwise broken or pinched. If you have vac being supplied to the head , yet nothing moves at all , suspect the head ..usually easily obtained from the dealer. If you observe it passes vacuum to an actuator (pull the line off and check), yet the door doesnt move ..you may have a stuck or broken door mechanism (rarer). Or a bad actuator (diaphram)

Edited by md4cars on February 7 2005 at 4:45 PM

Think you can answer this question?
Login or Become an Expert

DISCLAIMER: You acknowledge that any information you may obtain from individuals you contact through use of the Just Answer service comes from those individuals, not from Just Answer!, and that Just Answer is not in any way responsible for any of the information these third parties may supply. The site and services are provided "as is" with no warranty and no representations are made regarding the qualification of an Expert. Responses and comments on Just Answer! are for general information and are not intended to substitute for informed professional advice (such as medical, legal, investment or accounting) and do not establish a professional-client relationship. Just Answer! is not intended or designed to address EMERGENCY QUESTIONS which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service.

Just Answer! > Car Repair

Related Answers