View Full Version : Cause of sticking heater temperature control


Tony1M
02-22-2007, 07:41 PM
I just succesfully replaced the blower motor in our 1992 Accord LX 4AT, no AC, no power anything.

While I had the duct and fan housing removed I discoverd the ulitimate cause of the sticking heater temperature control sliderthat has caused great trouble and expense tomany owners of this generation of Accord.

As I moved the temperature sliding lever back and forth, I could easily see that the foam gasket of theforward-most flapper-door sticks terribly toits plastic seat on the heater-core housing.

I had to pull pretty hard on that front flapper to finallypry it loose from the gasket. Sticky stuff was on the surface of the foam gasket, as well as on the plastic surface where it seated and sealed.

This is the ultimate cause of probably tens of thousands of repeatedlystuck and broken temperature slider controls on these cars.

WhatI believehas happened fromDay 1 is that this chemically-improperfoam gasket gets stickyfrom the heat of the heater-core sittingmere inches away. Then, when the car is turned off, this sticky material hardens like a glue between the foam gasketand the plastic.

During the summer, there's not too much trouble, but during cold weather it is almost impossible for the cable to exert enough force to break loosethat stuck flapper.

When that cable fails, it's an extemely expensive thing to replace.We had ours replaced shortly after our warranty expired, and the bloody thing broke again within a year.Probably Hoda did not have a clue why this was happening.

I scraped off the sticky stuff on the plastic and removed as much of the sticky surface of the foam gasket as I could. I then considered what to do to keep those surfaces unstuck, soI coated the gasket itself, and the plastic surface it seals against, with a thick layer of silicone grease. Hopefully this will keep those surfaces lubricated enoughso that when the gasket softens again it will have nothing to stick to.

If this doesn't work over the long haul, I think the thing to do would be to cut some one-side-sticky paper to the same dimension as the gasket and stick it to the gasket with the not-sticky side facing the sealing surface. Thatshould be the final solution to the problem, and I'm kinda sorry that I thought of it only after getting the thing re-assembled.

sir_nasty
02-22-2007, 08:11 PM
how difficult is it to repair that issue? can you do it with duct still in? care to do another one of your fantastic write-ups for our DIY section??

Tony1M
02-22-2007, 08:25 PM
That intermediate white duct has to be removed to get at the flapper and its gasket. It's not too difficult to remove it, but it's more difficult to re-install it. That bloody metal strip that joins the duct to the fan housing takes some fiddling with to finally getits threaded holes lined up with the correspoinding holes in the plastic duct and fanhousing.

If the silicone grease doesn't fix it for good on our car, I'll take some pictures of the "final solution".

Honda should have discovered this problem, and solved it, in 1992 or 1993. Dealing with that sticky gasket should have gone part and parcel with replacing the slider cable. Not dealing with the gasket almost certainly means that any replacemnet cable will also fail one winter season down the road. Nobody in their right mind is going to give Honda ANOTHER $400 to NOT fix the same problem again.

ArcticHonda
02-22-2007, 11:46 PM
Are you talking about the slider controls on DX models or the Round dial type like the one below - or both?

local://upfiles/6435/3353EA6B301D497C96C72187FC98A194.jpg

hondadude
02-23-2007, 12:36 AM
ZING..... there it went ArcticHonda, right over your head

Tony1M
02-23-2007, 12:43 AM
I'm talking about the slider for heater airtemperature control. It's the bottom slider in this picture:
http://i2.photobucket.com/albums/y35/Tony1M/92heater.jpg
When the slider has been at the hot end (all the way to the right) for a bit of time, it is almost impossible to then move it more thanabout 1/4 of the way to the left -toward cooler air. If you force it, it will break the cable housing, and then you're eitherin for some expensive repair, or you have to unhook the cable where it attaches to the valve/flapper mechaism near the floor under the center of the dash. In the latter case, you're then in "manual" mode and you have to reach under there with your hand and manipulate things to get the temperature you want. My wife and I did that for many years.

rcy
03-22-2007, 12:01 AM
I have this same problem with my 91 Accord EX-R, which is the push button mode, with dials for fan speed and temp. I've noticed when the car heats up, the door eventually moves fine. In my car, it sticks in full cold. I guess this door let's air flow over the heater core? I don't think I have a coolant valve - I think hot coolant always flows through the heater core, and the door blends outside air in to control the temperature.

Tony1M
03-22-2007, 03:24 PM
Check under the hood near the fire wall - where the two heater-corecoolant hoses penetrate the fire wall. I think you'll see a valve on one of those hoses. Make sure it opens and closes fully when you operate your temperature contol.

Tony1M
01-05-2008, 11:47 AM
Just an update because of a new thread about this subject.

Our temperature slider has been working just great this winter. It's very nice to be able to adjust the temperature of in-coming air without having to be a contortionist.

sir_nasty
01-05-2008, 12:01 PM
Did we ever sticky a write-up on this in the DIY section or should I move this one over?

Tony1M
01-05-2008, 12:22 PM
What would be nice would be, as you suggested in an earlier post, to have photos to accompany the steps of the job.I could have killed two birds (blower motor replacement and testing, and flapper troubleshoot and repair) with one stone, but although I like the HAF very much, I don't like it enough to go through the job again just to take photos!:) (Like I've said on more than a couple of occasions, people should take and postmore photos of the various jobs they perform after getting advice on them here on the HAF. That would be a tremendous aid to others and probably the site would be much more popular as a result.)

However, even though there are no photos of this job, I'm sure our car is not alone with this nag of aproblem, so I thinkthere should at leastbe some mention ofit in a prominent place.

(Literally every time I operate that slider I'm reminded of what we had to go through for years without being able to use it. My overallattitude toward the car changed remakably after I finally got it fixed.)