engine and drivetrain What's wrong with my heater?

[jrhone]

So now that it's really cold I am seeing some odd things in the heater operation. First there is constantly air coming into the car from the heater box no matter what settings are used. It varies with car speed so engine compartment air is getting into the cabin through the airbox. Thus isn't right is it? Then if I switch to defrost about 15% goes to the vents in the dash and the rest still comes out of the heater box. It should route all the air to he dash vents shouldn't it? The air constantly coming into the cabin is lukewarm whn the heater slider is on off but when I slide it to heat the air gets colder. That's not normal.

[Mike Self]

First there is constantly air coming into the car from the heater box no matter what settings are used. It varies with car speed so engine compartment air is getting into the cabin through the airbox. Thus isn't right is it? Nope--I suspect the cold air mixer door is stuck in the open position. When operating properly, the temp control lever closes the mixer door as the hot water valve is opened, so with the lever to full hot, the valve is fully open and the mixer door is fully closed.

Then if I switch to defrost about 15% goes to the vents in the dash and the rest still comes out of the heater box. It should route all the air to he dash vents shouldn't it? Yes, but only if you have the floor vent lever closed, and it's actually closing the floor flaps. Work the floor lever and put your hand on the flap to see if it's moving.

The air constantly coming into the cabin is lukewarm whn the heater slider is on off but when I slide it to heat the air gets colder. That's not normal.

Nope, it isn't. Possibly a PO reinstalled the water control valve lever upside down; then when you move the control lever to cold, you get warm air and vice versa. Easy to check--put your hand on both sides of the valve with the control set to hot; if the hose is hot only on one side, it's backwards. Eas fix too; just reinstall the lever in the opposite position from where it now is. If the lever sticks up above the valve, reposition it below or vice versa.

The other control lever problems may require removing the heater box to repair. Lotsa tutorials on that job; check the archives.

mike

[02for2]

Don't know how long you've owned the car, or what service/repair may have been done to the heater box.

Assuming nothing, it's a safe bet that ALL the foam has degraded or totally disappeared.

A heater Box refurbishment is in your near future, assuming you want to fix the issue.

I've seen many here post that it's a dreadfull repair - obviously, these have never owned a Lotus, a P Boxster or even a Z-Car. I have, and compared to these, the Heater Box repair on an '02 is a piece of cake by comparison. On an early Z-Car you have to literally cut the core out of the box.

If you drain the coolant, removing the box and the accompanying cables is easy - maybe 20 min. max - especially if you do not have AC.

Then disassemble the box - 1 Hr., clean and strip the flaps - 20 min. Install new foam - 20 min. and reinstall the box - 20 min. Add another 45 min. if you're replacing the fan and refurbishing the heater core (which you should do). This does not include a 24-HR soaking of the core in vinegar to remove any scale. Reassembly and reinstallation s/b 1 Hr. unless you're dogging it. I know - I just completed a total refurbishment last week.

So, figure 3.75 Hrs. to complete the job. 3.75 Hrs. working time every 30 yrs. is not a big deal. Do it right and be done with it!

Cheers!

[c.d.iesel]

.....flaps not working correctly

somethings broken?

somethings loose?

cable's fuched up?

fat-arsed mouse's butt is preventing

a flap to close?

[FunElan]

You have a defroster!?

Mine does the same luke warm thing, i don't think my heater valve is connected actually....

[JohnP]

I had a similar issue when I took possession from PO, only in reverse - constant warm air coming in the floor (annoying in summer), and couldn't shut it off. Didn't have knowledge, time or confidence then to fix so enlisted help from an experienced 02er. The heater valve had been installed backwards, the linkage to the flaps was not propoer and the foam on the door flaps had come off - straightforward and common fixes on heater box renewal. I'm still a beginner in many respects, but I've gained enough confidence doing other stuff on the car (with great help from the FAQ and one of the responders to your post) to consult the primers avaiilable here and try and do it myself the next time.

[Lars]

Thanks for the help on this one. Mine was doing the same thing, although I am running a spare CRX valve that has to be opened manually. But I had the cold - warm setting to cold allowing the cold air in. I changed that and it got toasty in the car. Felt good for it being 15 degrees out.