My 96 accord is overheating. If I am driving there is no problems. When I idle or am in traffic the system gets very hot. I have put in a new thermostat and new fan switch. The fan motors will not turn on. I have checked the fan motors and they are good.(jumper wire to battery). Fuses are good and relay is also good. I can disconnect the fan switch and jump the circuit and the fans will turn on. I can also jump the low pressure switch on compressor and fans will turn on. They will not turn on by themselves. I also removed thermostat and system does not overheat and the fans will not come on. Again I can jump them at the fan switch and they will work. Totally confused and not sure what to do.

 

Both cooling fans should turn on if you jumped the harness connector to the switch; which you said they do. That would indicate the power and ground sources, and relays are okay.

Issue may then be either:

• the coolant temperature at the switch is not at the threshold for the fan switch to close (e.g., above 199 degrees F). Also make sure all large air pockets are purge from cooling system. Most of the air purging occurs after the thermostat has opened.
• faulty or wrong replacement fan switch

 

I have put two new switches in(second one closes at 175 degrees) and still no luck. The temp is getting way past 210. At Idle in driveway I will jump fans and temp will fall, but cant do this in traffic. Thinking about pulling thermostat and closing circuit by connecting wires at switch. This is my kids car and I don't want him to blow a head gasket. If he does that I will blow a gasket!

 

Your description suggests that coolant temperature sensor may be faulty; ie coolant is not as hot as temp gauge indicates.

Suggest use of IR thermometer to check thermostat housing temp.

good luck

 

Ok, two questions 1) Where is sensor located, 2) If it is bad what is it controlling. Thanks for your help

 

On 4-cyl (don't have V6 manual), it has a single wire (red) connector and is located under the distributor.

On 4-cyl, the ECT gauge does not supply input to ECM. There is a separate two wire ECT for ECM.

You need a shop manual for your vehicle. suggest checking ebay.

good luck

 

I think the sensor your are after is next to the block. Follow the lower radiator hose to the block, between the thermostat and the solid coolant line that runs around the head there is one electrical connector that clips in straight down. This sensor measures the coolant temperature. Again I think that is the right one. If it does fail and it does not read the temperature correctly or at all, then it will not send a signal when the engine has reach maximum temp and thus the fans will not turn on. I stress that I think that is the one, but it has been a long time since I last worked on that generation v6, as you have a rare breed. Good luck.

 

One additional thing, it sounds simple but is your coolant level full. If there is air trapped near a sensor it can also get a false reading that way.

 

The coolant level is full. Again today driving the interstate no problems as soon as I exit temp goes up, I have the fans working all the time by jumping the circuit. I thought I had system bleed. I am now leaning to a busted head gasket or a blockage in radiator. This would seem odd though, because if I run vehicle with no thermostat I do not have a high temp problem. I will check coolant when engine cools, if low on coolant at that time and no visible leaks in system does this seem to be bad head gasket?

 

A cold leak-down test of cooling system can confirm or refute a leaking head gasket.

There is also a chemical test on coolant that can detect any combustion gases in coolant.

good luck