I have a 1990 Honda Accord EX with 225,000 miles I just purchased and its marked "Salvaged" on the pink slip. It doesn't overheat during normal driving conditions but will get a check engine light after going uphill and will come close to the red on temp gauge at high rpms. I took it in for smog (transfer ownership) and failed smog 1st time due to EGR so I replaced the valve and cleaned the intake manifold as well as changed plugs, air filter, radiator flush, oil/filter and thermostat (not an easy task for a beginner) and when I returned for retest, the emission was better (NO {PPM} 15 mph 1st test 2017 2nd test 1361; 25 mph 1st test 2505 2nd test 1327) but it failed due to improperly working cooling fan not to mention the test burst my heater hose on passenger side and drained all my coolant at the test station. I had noticed prior to taking it in for testing that the temp gauge stays just below dead center as long as I drive at 3000 rpm or less but if I go faster or drive uphill, I'll get a CHECK ENGINE light (it shuts off when I turn off the car and on again). Today, with car off, I jumpered the fan and it works, I grounded Coolant Temp Switch B (attached to housing where upper hose meets the engine) and it triggered the fan but when I tried to ground Coolant Temp Switch A (located on thermostat housing), it did nothing. I then turned ignition switch to on then tried to ground it but I kept hearing click sounds only. Relay is good, fan assembly is good, replaced damaged hose, no leaks whatsoever, thermostat is good because lower hose gets hot at right temp, Switch B is good because the fan activates at super high temps but switch A not doing its job. I just replaced switch A today and still no luck. Gauge will stay just below half but will get extremely hot (but not in the red) and get a check engine light after holding at 3000 rpms for a few seconds. I'm inclined to think its bad wiring at switch A but I need advice before I proceed. Would be nice to drive faster and uphills without worry so I can visit my son (liver transplant) at Stanford, hour and a half away. Any help would be appreciated! Thanks!

 

Since the check engine light is turning on, you need to check the computer for codes. The common DIY thread on top of the gen tech help forum has a link to checking engine codes. Post the codes on here.

Lets start with some basics for the cooling system. When the engine is cold, start up the car and turn on the a/c. Do both fans on the radiator turn on?

 

10 IAT - intake air temperature sensor. I used the paperclip trick and got one long flash to get that code. I got my last check engine light in park with the hood up while holding down the gas at 3500 rpm for maybe 20 seconds. And when I turn on the AC during cold start, neither fan turns on.

 

Code 10 is the intake air temp sensor. Was the check engine light turning on before you did the work on the intake manifold? I would check the electrical connection first for any damage. It is #21 in the picture.



For the fans... Does your a/c work? Do you have a volt meter?

 

For the fans.....Don't ground thermo a (t-stat), jump the wires together.....if I'm reading this correct. Then see the link below and see if it helps.

https://www.hondaaccordforum.com/for...similar-44973/