A neighbor asked me for some help with his '93 EX Coupe - stock w/ D16Z6. He said it was running warm but would cool down when going down the road. He said the radiator fan was not running.

The coolant level was low, so I topped that off. I jumpered the connector at the ECT on the head (C105) and the fan did not come on. I did run power direct to the fan connector and the fan runs.

The highly regarded Mssr @wxman94ej1 advised me that there is also the Coolant Temperature Switch at C105 to deal with, not just the ECT

Do I need to jumper the connection at C105 to get the cooling fan to come on?

Sorry for a potentially lame question - I think my B18C1 just has the ECT in the head and the relay to deal with...

 

The coolant temperature switch on the thermostat seems to be the only thing that can turn the fan on. The temperature switch / fan relay circuit is also wired to the ECU but I think that is only an input, similar to the power steering pressure switch, so that when the switch closes, the idle speed will be increased for the extra electrical load.

 

So the ECU cannot tell if the switch is bad and give a CEL, eh?

Thank you!

 

OBD1 really doesn't set out to do much more than make the car run.

 

Thanks. Do you have any pics of this connector? The drawing makes it look like it is on the back of the head? Or the side oriented towards the firewall...

 

The relay in the fuse box under the hood? That's in the power circuit. If the relay is dead, the fan won't turn on.

 

On my OBD1 JDM B16A, here's where they're located:



And a closer pic of the C105 on the thermostat housing:



Basically, follow the lower radiator hose back into the engine bay and it should be right at the end of that hose where it connects to the thermostat housing.

 

Yeah, I went relay after I couldn't get the fan to run by jumpering C109. Didn't have a lot of time, trying to help the guy out. I wasted $45 of his $ b/c I checked relay last night and it clicks like a **** when you power C &D... We'll see if the dealer takes it back if still sealed.

 

Thanks. I will follow the lower hose

Uh, wait, what?

Funny how different the D16Z looks to me. I have not had one of those in my engine bay since '02...

 

Unplug 105 and jump it. Turn key on-- fan should run. Test drive like that, if no overheating replace the thermo switch. If it still overheats with the fan running all the time, there is a different problem.

 

Yep, fan does run when you jump that connector. His radiator has a leak so I am going to replace. Hopefully we can find a switch today.

Thanks

 

If there is not enough coolant to flow through the radiator, the engine will of course overheat...
yet the fan will not run because no hot coolant reaches the thermo switch.

So don't conclude the switch is bad yet if there is another problem with the system.

 

Check the fan switch 1st before buying another.

 

I agree with the value of solid diagnostics, I just don't have time, and they don't have the ability to check on things. I went suspenders and belt - we did coolant switch, radiator, Honda blue,oil & filter, fuel filter, plugs, cap rotor (old plugs - OMG) distributor o-ring and VTEC "filter".

I wasn't going to replace the radiator, burp the cooling system, and trust that they wouldn't over heat it again, then go back next weekend and replace the switch if needed, burp the cooling system again - ain't nobody got time for that...

Good news is there was no oil in the anti-freeze and no coolant in the oil.

Sad thing was there were metal flecks on the VTEC filter. They had run it so low on oil once it needed 3 quarts. It has a slight knock after the low oil incident. What weight oil would you all run to help with that?

 

Knocking noise is worse now. One recommendation I am hearing is to replace the D16Z6 w/ a JDM D15B for much less coin. I do not know much about D swaps, what say you all?

 

So did the fan switch fix the fan issue? Cooling issues resolved but now a motor problem?

I'm not very knowledgeable when it comes to actual engine problems. Seems like the D15B might be a decent option. Also maybe try and source a used D16Z6 locally? As far as I know, it would seem like a D for a D might be a pretty straightforward swap. Sorry I can't be more help!

 

as just a driver? any 88-00 d engine can work.

 

Yes, cooling system good - but the engine is not so good. The metal flecks in the VTEC screen were not a good sign...

 

Thank you!