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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Jeff wrote:

==================================== 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'

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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)

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

-SP

Jeff wrote:

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Speedy Pete wrote:

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

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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

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Jeff wrote:

==================================== 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'

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Jeff wrote:

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

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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 "78C" 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.

--
Tegger

The Unofficial Honda/Acura FAQ
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Interestingly, there is a thread in alt.autos.ford with the same complaint, a new aftermarket thermostat, and the same recommendation.

Mike

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