Good questions, lol Fuses usually pop when a wire shorts to ground somewhere. I would check all the wires in that circuit real good. I think your problem is a wire somewhere in the circuit. What happened after the fuse was replaced? did you let the car warm up and did the fans come on? I would do this first.

 

Yes I let it warm up after replacing the fuse and the fans did not come on at all. I already looked for obvious shorts but will investigate more today. I think it needs a temp. switch also.

 

You can make sure the circuit is good downsteam of the temp sensors by simply jumping the two wires in those green connectors. However, they are designed to come on at different times. If I'm not mistaken, the one on the thermostat housing should activate when the car is running and the one in the front should activate when the car is off. So, jump the connector on the thermostat when the car is running and both fans should turn on (at least they do on my 5th gen). Jump the connector in the front when the car is off and just the radiator fan should turn on (again, on my 5th gen). I just had a problem similar to this and it turned out to be the fan timer (behind the glove box). However, I didn't have a blown fuse.... Like Hondatech said, there's usually a short to ground for a fuse to blow.

Did the fuse blow again?

 

Here are the results so far.....

The fuse has not blown again
Jump relay - big fan comes on
Jump rear temp. switch - both fans come on
Jump front temp. switch - neither fan comes on

 

I just want to check... I don't have a '90 so I'm not sure...

Explain the 'front temp. switch'. Are you sure it's not the ECT sensor which is wired into the ECM? That one has nothing to do with the fans.

When you jump the 'rear temp. switch' the fans run. Now have you run the car HOT and the fans don't run - even with a good fuse? Then that fan switch is bad. Remember, it's setpoint is hotter than the normal temperature, so the temperature gauge will go a little high before the fan comes on. Not all the way up into the red, tho...

 

There are two switches with green connectors, one is on the rear side of the motor (towards the cabin) next to the intake and the other is on the front side of the motor (towards the grille) next to the exhaust.

Yes, when I jump the rear switch both fans come on and when I jump the relay the larger fan comes on. Yes, the new fuse is still good. Now, about this HOT. Well, I just did the head gasket and don't want to fry it again. Here is what I did (perhaps it wasn't hot enough), after I put in a new fuse and jumped the switch and seen that both fans came on and knew the motors worked I went and drove the car about 20 miles @ 60MPH and came back home. I turned the car off, opened the hood and the fans were not on. So did I run it hot enough? The gauge never got past 1/3 up. Should I drive it and then let it sit running and wait for them to come on? I just don't want to fry it again.

Thanks to all for helping me help my Mom.

 

How long (how many miles) on the headgasket? I don't want you to trash that...

When you drive 60mph there way more air going thru than the fan can possibly blow. Drive it to warm it up, then park it & leave it running. Maybe hold at 2500rpm or something. Just watch the temperature gauge. It might get to 1/2 or maybe a little more before the fans come on. Be prepared to turn it off if it keeps climbing, or just drive it to get air moving... Park where you can just pull out & drive? 30mph probably pushes more air than the fan.

There maybe was a 2nd fan switch, with a different setpoint, that operates after you turn the car off? My cars don't have that at all, but maybe back in '90?? Someone with a '90 will have to describe the location of the ECT sensor vs. any 2nd fan switch...

 

The new head gasket has exactly 33 miles on it to this point. I'll go take a 30MPH drive around the block and park it and let the gauge get 1/2 or 3/4 and watch the fan and see what happens.

 

I drove 5 miles @ 30MPH and parked the car running with the hood open and about 2 minutes later with the temp. gauge at 1/2 both fans came on. It seems the fuse was the problem in the first place and is the blame for the blown head gasket that I just replaced. I understand that I need to find out why the fuse blew in the first place so I will now look futher into the wiring.

Many thanks again to everyone that has helped me!

 

Well I think I may have found why the fuse blew. I just took it for a long test drive after all the head gasket and fan work to see make sure it was road worthy and an aweful noise began to shreek from under the hood. The larger fan was making a roar and clunk sound and was spinning on and off irratically. Obviously this fan motor is on it's last leg and will be replaced soon. This leads me to ask, would a fan motor locking up on and off like this make the fuse blow? To me it would but I want a second opinion.