84dime

Ok so i did a mini-me swap on my girlfriends 98 civic but the cooling fans will no come on. If i turn on the A/C the A/C fan kicks on but not the radiator fan. If i unplug the coolant temperature switch and jump the wires the fan kicks on. The coolant temperature switch is one on three new ones that i bought. I swapped out the fan relay with the other relay that is in there as well. New fuse as well.

So correct me if im wrong but all i can conclude from this is the ECU is screwed up.

Any ideas? what temperature should the fan kick on?

integratyper1990

Try changing the coolant temp sensor or make sure that the plug is on there snug. (this is not the coolant temp switch IT IS DIFFERENT)

Former User

The ECU has nothing to do with the radiator fan. Try bleeding the cooling system.

Bleeding the cooling system may take 20-30 minutes.

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push/turn the dash heater lever/**** to MAX heat. Fan need not be on.

3) Follow the directions in the diagram below

84dime

Coolant temp sensor is brand new and working according to my obd2 scanner.

I did the bleeding procedure for about 45 min and the temp on my scanner kept going from 189-191 but not any higher and it was 85* out today.

Not sure why it wouldn't get any hotter but if i drive it for awhile it will start boiling coolant out of the overflow because the fan never turned on. This only happens if i drive for more than 30 min or so.

Any other ideas? Thanks for the help guys

Former User

You may have a blown head gasket that is blowing exhaust gas into the cooling system. The gas pocket may prevent coolant from registering the correct temp at the switch and sensor. There's a kit available for measuring exhaust gas in the coolant.

84dime

I shure hope not since i just got the engine back together after rebuilding it. I had the head and the deck machined and used a honda head gasket. I dont see any air bubbles like i did before i rebuilt it.

virgineg6

you could test the rad fan switch by putting it in boiling water an check for continuity across the posts

Former User

The coolant temp sensor is different than the coolant temp switch.

84dime

Right... The coolant temp sensor tells the ecu what temperature the coolant is where the coolant temp switch closes contacts at a certain temperature to turn on the fan.

Does anyone have a wiring diagram of the cooling fan system?

Thanks

Mad-Mike

iTrader: (1)

Bump, I'm interested in the diagram too, I am having somewhat of the same problem with the fan not coming on.

Former User

Mad-Mike

iTrader: (1)

Stupid question but would a bad condenser fuse not make the radiator fan come on?

Former User

Yes, but in this case, the A/C wouldn't work. If you can jump the 2P fan switch connector and the radiator fan runs with the key in ON(II), then the fan circuit and fuse is fine.

motegicivic

Does the temp gauge go past 1/2? The fan will not come on unless it goes slightly past 1/2 way up?

Since you did a swap, did you put in the proper thermstat? That can affect when the fan will kick on as well.

Former User

A reading of halfway or higher indicates overheating.

motegicivic

Ron my gauge is half way up (right at the temp symbol) since new and that is close to 15 years.

Note 96 civic EX.

Former User

In general, the normal temp position for our Civics is about 1/3 or just slightly higher, not halfway. Can't say why yours reads higher. Using a scan tool, what is the range of your coolant temps from the ECT sensor at normal operating temp?

96electronH

make sure if you got an aftermarket coolant fan switch that the connector snaps into it. i got a fan switch from autozone and it doesnt fit well at all. you can back probe the connector at the switch and see if you get continuity when it warms up.

motegicivic

I do not have a scan tool, but maybe since you have a dx it is different.

Also, we have to take into account these gauges are just visual guidelines, and never 100% accurate.

96electronH

very true my buddies eg has always sat lower than half way but my ek has always sat dead in the middle.

Former User

I have 97 DX and 00 EX Civics and both temp gauges behave identically. Many members on this forum have reported that their temp gauges also read below halfway at normal operating temp.

I would be concerned by a halfway reading.

96electronH

i have been driving my car for four years no problems halfway reading...

Former User

Just sayin'

84dime

So by looking at the wiring diagram, if you jump the coolant temp switch connector and the fan comes on then everything in the circuit is working properly and either the switch is bad or the car is not warming up enough to close the contacts on the switch or there is a bad connection between the switch and connector.

Any other ideas?

Thanks guys for the help

84dime

Bump