Cooling Fan stopped working

My (single) cooling fan stopped working yesterday, and of course yesterday was the first hot day of the year!

I've never really messed around much with electricals before.

Anyway, the 2 fan fuses (#10 & 15) seem fine, not sure which one is in-line with my fan.

Not having built the car, near as I can tell it looks to me like the fan plug has power to it from the harness (2 power wires), a power wire from the plug to the fan motor, and the wire from the thermo switch in the radiator to the plug.

I assume the thermo switch controls whether power gets to the fan motor through the fan plug based on the radiator temp, and it does this whether or not the engine is on, as the fan used to always run for a minute or two after shutting the engine off.

I don't know if the wiring for the fan goes through one of the OEM slow speed resistors or not, but I doubt it as I never noticed two different fan speeds, although I really wasn't paying much attention to it until now.

Anyway, does this sound like the thermo switch is shot?

The switch looks like 1/2" thread, I assume I can replace it with any 1/2" thermo switch?

The temps never got much more than a hair above the 1st hash mark on the temp gauge before, which I've read is the 80C mark, so I'd need what, a 85C thermo switch? 83C? Higher?

Let me know what you think!

Ok, the car's builder said it's just a straight power line from the battery to the plug of the fan and the thermo switch completes the ground. There is supposed to be an in-line fuse too, that he thinks is probably burned out.

So it turns out that the fan plug is bad.

This plug has power in, power out, and the wire from the thermo switch in the radiator.

This is printed on the plug, MAS looks like the manufacturer:

MAS
REL40 12VDC
12V 30/40A

and also an elec diagram.

Any ideas where I can find another plug?

Sounds like its just a normal relay... Does it look like this? [You must be registered and logged in to see this image.]

You can get those at any eletronic stores that install car stereos ect.

Those relays are known to blow when used with fans because they can't handle the voltage spike that goes thru them.

You should try and find a 50amp relay

That's the one spence! I'll look for a 50A.

Thanks!

no problem... I think other people might even be using a 75amp relay to run fans

Thanks, as I said above, I've never messed around with auto electrics much before. The inline fuse is 30A and it didn't blow, why do you suppose the relay fried out?

As i understand it the voltage spike happens only when the fans first come on and only for a couple milliseconds and it wouldn't be long enough to blow the fuse. I'm no electrical guru either... I'm only going by what I have read.

Thanks spence.

Actually, the relay in my car has 5 prongs, not 3. Two prongs are connected to the power from the battery, one is power out to the fan, one is connected to the thermo switch in the radiator, and the 5th one is not used.

I don't know what the difference is between 5 and 3 prong relays.

Could I use a 3 prong instead? One power in, one power out, and one to thermo switch?

The 5 prong relays are common. The 75amp relays have 4 prongs which would work for you. Then you'd never have to worry about it blowing again.

[You must be registered and logged in to see this image.]

And you'd wire it like this

[You must be registered and logged in to see this image.]

Thanks spence, I've been googling around and reading up on them, pretty simple stuff, really.

Anyway, I'm calling all the Pep Boys/Autozone-type places near me, but they don't seem to have generic relays, they're all asking me for make and model or part numbers.

I'm still searching...

acorad wrote:Thanks spence, I've been googling around and reading up on them, pretty simple stuff, really.

Anyway, I'm calling all the Pep Boys/Autozone-type places near me, but they don't seem to have generic relays, they're all asking me for make and model or part numbers.

I'm still searching...

They do have generic 25 or 30 amp relays. Ask for fog light relays. I forget where you live but I'd give you one as I bought a few extra to keep around. I'll be in Lodi tomorrow for traffic school, and am in the Pleasanton during the week.

Thanks Dawg, I can find plenty of 30's but I'd like a higher amp like 70 so I don't have to bother with this again. My local Fry's carries 70's but they're not in stock, Radioshack only has 30's.

acorad wrote:Thanks Dawg, I can find plenty of 30's but I'd like a higher amp like 70 so I don't have to bother with this again. My local Fry's carries 70's but they're not in stock, Radioshack only has 30's.

I had to order mine off ebay. No local sources had them. I used two 75 amp.

[You must be registered and logged in to see this link.]

1 day ups to Cali.

The big secret is if they have RH's radiator, get the damn relay OFF the radiator. They don't like water.

Dawgz83948 wrote:

acorad wrote:Thanks Dawg, I can find plenty of 30's but I'd like a higher amp like 70 so I don't have to bother with this again. My local Fry's carries 70's but they're not in stock, Radioshack only has 30's.

I had to order mine off ebay. No local sources had them. I used two 75 amp.

[You must be registered and logged in to see this link.]

1 day ups to Cali.

The big secret is if they have RH's radiator, get the damn relay OFF the radiator. They don't like water.

Yup, RH radiator and it's mounted on the lower fan.

I order stuff from McMaster-Carr for my biz all the time. Just did a quick search and yup they have relays.

I ordered a Weatherproof Five Pin High DC Inrush Current Relay w/mounting bracket, also called "automotive relay."

Supposedly it can handle a high-inrush current of 150A and has a mechanical life of 1 million cycles.

Less than $9, part #9672K44, and it'll be here on Monday.

Sounds like it should work, no?

Yup. But I highly recommend moving the relay off the radiator. It had no business being there in the first place.

acorad wrote:

Dawgz83948 wrote:

acorad wrote:Thanks Dawg, I can find plenty of 30's but I'd like a higher amp like 70 so I don't have to bother with this again. My local Fry's carries 70's but they're not in stock, Radioshack only has 30's.

I had to order mine off ebay. No local sources had them. I used two 75 amp.

[You must be registered and logged in to see this link.]

1 day ups to Cali.

The big secret is if they have RH's radiator, get the damn relay OFF the radiator. They don't like water.

Yup, RH radiator and it's mounted on the lower fan.

I order stuff from McMaster-Carr for my biz all the time. Just did a quick search and yup they have relays.

I ordered a Weatherproof Five Pin High DC Inrush Current Relay w/mounting bracket, also called "automotive relay."

Supposedly it can handle a high-inrush current of 150A and has a mechanical life of 1 million cycles.

Less than $9, part #9672K44, and it'll be here on Monday.

Sounds like it should work, no?

Dawgz83948 wrote:Yup. But I highly recommend moving the relay off the radiator. It had no business being there in the first place.

Will do.

I have the RH radiator as well and the relay was also mounted to the lower fan mount.....It blew and caused me alot of grief. Absolutely stupid place to have a relay. I replaced it with a 70 amp tyco relay and have never had a problem (with the relay) since.......But then, the cheap crap RH fan that came with the radiator failed and this wasnt a failure like it doesnt work but the kind where it drains your battery and the magnets of the motor fall out. Horrible.

Look at replacing the RH fan when you get a chance.

Thanks LT1. The radiator has also now sprung a leak. The rad in my Durango has 180k+ trouble-free miles on it, the rad in this car has less than 10k miles on it. I guess my next step is to research the hell out of radiators!

Now THAT sucks. RH charged me a grand for the radiator set-up so a leak at 10K is absurd.

I bet you could send it back to ron davis to have it fixed; atleast for a small fee.

944-LT1 wrote:Now THAT sucks. RH charged me a grand for the radiator set-up so a leak at 10K is absurd.

I bet you could send it back to ron davis to have it fixed; atleast for a small fee.

Good point, I'll contact them.

acorad wrote:

944-LT1 wrote:Now THAT sucks. RH charged me a grand for the radiator set-up so a leak at 10K is absurd.

I bet you could send it back to ron davis to have it fixed; atleast for a small fee.

Good point, I'll contact them.

I took mine to a local radiator shop and they fixed it up for $25. Place I used was Modesto Auto Electric.

Well, the radiator is at the shop getting repaired. Turns out some of the tube-to-header joints were leaking, and the shop is expoxieing them. And also preventively epoxieing most of the others, just in case.

I called Ron Davis and they said to bring it to rad shop and have it epoxied. They said the rads leak if they're not mounted correctly, and that they stopped making rads for RH because of these types of problems.

I called RH and they said I could either ship the rad to them, and they'd charge me whatever their rad shop charged them to fix it, or just find a local shop to fix it. They also recommended epoxieing it. They also said it has to be mounted correctly or it will leak.

I had a long talk with them about how to mount it correctly and I'm pretty sure it was mounted correctly (gently held w/in the soft rubber nubs of the mount).

Anyway, that's what's going on.