No Heat in 1990 Honda Accord Dx

I am still trying to put my finger on why I have no heat. In the
summer months I was seeing lots of movement in the Temp display. So I
replaced the original radiator, and then the thermostat. All
fluctuations stopped, and it ran much cooler from then on.

Now I am seeing no heat. I wondered if the control valve was sticking,
as the "slide" for temp control resists staying all the way over to
heat. It "bounces" back toward the cold going no more than 3/4 the way
to the right (heat). Before I go and tear apart the dash to get to the
heater core, is there anything else that I can check? I did try
putting cardboard in front of the radiator to see if it is just running
too cold. There was some improvement, but still nothing like it used
to be.

I'm open to any suggestions, rather than to go see the dealership that
want's $1125.00 to replace the heater core.

Thanks,
Jeff

 

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Start under the hood, and you may have to slip off the intake so you can
get at the water valve on the heater hose. If you don't mind LOTS of
heat just disconnect the control cable and put a cable tie or wire
around the 'tap' to hold it open.

'Curly'

 

I hope you used a authentic Honda Thermostat.(OEM)
Aftermarket ones are questionable,and you may get the wrong temp TS for
your vehicle.(on my Integra GSR;their cross-ref book said 180degF instead
of the proper 195degF TS)

You could have some crud blocking a hose (or that valve),maybe a backflush
is needed.

I believe the use of OEM HONDA antifreeze is also recommended instead of
aftermarket brands.
(IIRC,they allegedly cause early death of the new radiator)

 

Either your heater valve isnt functioning or the heater core is blocked.
Your turn to investigate which one is the problem

-SP

 

Thanks to all of you who have answered my questions.

I have since checked the heater valve, and It does seem to be
functioning. I can visualize the valce opening and closing.

As for a question about the thermostat, I did not use a Honda OEM
thermostat, I used a new aftermarket 180F thermostat, but have been
unable to locate the documentation to identify if that is in fact the
correct set temp, or if it should have been 195F.

I am now wondering about the heater core, and wondering if there is an
easier way to backflush it, or test the flow through it. I imagine
that I can just disconnect the hoses and see if there is any flow or
not. Does this sound right? Also what type of flow (volume) am I to
expect? Low or high volume that should be circulating? I will be
trying to check these problems out in the next day or so, so any
further advice would be great.

Thanks again to all of you for your responses,
Jeff

 

You might want to do a confidence check on circulation before disconnecting
the hoses. I gouged myself rather badly on the cat heat shield when pulling
off one of the hoses to the control valve. Anyway, with the engine warmed up
and the heater on, you can shut down the engine and grab each of the hoses
that attach to the heater core. If both are hot - more than just casually
warm - you have coolant flow through the heater core and the air isn't being
directed properly. Also have somebody turn the temperature knob and watch
the lever on the heater control valve. If the lever doesn't move you're on
the trail of the problem; next place to look is the control assembly at the
bottom of the center console (way under the radio). That is accessible from
the passenger side.

I've seen a lot more stuck heater control valves than plugged heater cores -
in fact, I haven't seen a plugged heater core in almost 40 years of working
on clunkers. Lots of leaky ones, but no plugged ones.

Mike

 

=====================================

When you changed your thermostat, did you fill the reservoir to MAX like
it says in the owner's manual? You'll have to check it again or you
won't displace the trapped air in the heater core and block. I keep mine
at MAX and it never changes level summer or winter, hot or cold.
Sometimes more drastic measures are required to remove ALL the air, but
you'll at least find out if your heat problems are real.

Keep in mind if your coolant was that low, head damage could result.

'Curly'

 

Most of todays thermostats are just plain JUNK!

I have replaced most in my cars on a semi-annual basis and it doesn't
seem to be affected by how much I pay for them.


I have put 180 and 195 thermos in my hondas with no discernable
differences other than where the temp needle resides.

-Pete

 

@f1g2000cwa.googlegroups.com:

Well, that explains quite a lot.

Your car uses a thermostat that begins to open at 172F. It is fully open at
194F. Such a thermostat -- if high-quality -- will display the notation
"78ºC" upon it.

Perhaps you may wish to install the sort of high-quality, properly-rated
thermostat Honda intended when they spent 100 million dollars developing
your motor.

That high-quality, properly-rated, properly functioning thermostat is sold
for about thirty bucks at your local Honda dealer.

Install one of those first, then see if you need to gripe here any more.

 

Interestingly, there is a thread in alt.autos.ford with the same complaint,
a new aftermarket thermostat, and the same recommendation.

Mike