I've discovered my 89's fuse and relay for the cooling fan very hot. (this fan is the one in front of the condensor)

The fuse is #7 and someone in the past had spliced an external 30A fuse from it as the #7 fuse holder melted. Unfortunately the external 30A fuse is also hot and has melted a bit of the ashtray above it is in contact with. The relay for the fan (silver relay marked J) is also hot. I've tried swapping a new relay but the new relay also became hot.

My AC fuse #16 is also hot but that's something known and discussed in the FAQ. I'm thinking of getting a new fuse panel since I have 2 melted fuse positions (#7 and 16). But with the heat generated by the fan's fuse I'm afraid it'll just melt the (new) fuse panel again.

Anyone else having the same issue with their cooling fan? What can I do to make things cooler?

Thanks

Hi again,

Relay J is for your cooling fan at the radiator
Fuse 7 is the series fuse via a Green/Red wire through a 4 pole connector
"F" near the drivers side firewall (Not sure which side)
and on to the radiator switch.
I understand your hesitation about frying your ammeter, so here's a plan:
Pull fuse 7 , disconnect your negative battery terminal,
and pull the connector off of the radiator switch.
Then measure each side of the switch connector to ground. (Fan hooked up)
You should see 6 ohms on the fan motor side looking at the motor winding.
You should see infinity on the fuse side.

Post back... Include your e-mail if you want to speed up things.

Bill

Hi Bill

Thanks for the reply. Been busy taking apart the fan. I only read your new reply after I have finished dissecting my cooling fan.

This is what I've discovered. The harness to the fan motor is crumbling away and exposed especially where it crossed in front of the fan. The front bearing is almost seized. It's a wonder the fan could still turn. The rear bearing is making a grinding noise. All 4 carbon bushes are down to 1 cm length.

I need to search for a new fan first. For now I've covered up the remaining exposed harness. I've also disconnected one of the radiator switch connectors. And put back my fuse 7.

I'll see how it goes with regards to J relay and fuse 7 temperature with this setup.

Thanks again.

Didn't you say the relay was getting hot with the fan unplugged?

Take the resistance measurements from my last post and tell me what you have.
that will verify if your harness is OK.

Bill

Hi Bill

Did you get my email? I clicked the mailbox icon in your profile. I recall there was spamming issue on BB previously, so I dare not put my email out in the open.

I measured infinity on both sides of the connectors to the radiator switch.

Based on a few days worth of observation, (new) relay J is warm, not hot. There must be another circuit this relay is controlling besides the power windows and the fan which I can't pinpoint.

Thanks

Hi ____?

I didn't get email from you.
Just put your email as whatever AT whatever DOTCOM
or get a throwaway yahoo email drop. If you want to get rid of spam
get a new email account and move to Puppy Linux.

Does the fuse blow with the radiator switch unhooked?

Bill

Hi Bill

This thread is getting long. I'm going to install a new (used) fan tomorrow and use a 25A fuse for it as is was originally designed by volvo. I'll post a new fresh thread once the new fan is in the car, and work my way from there.

No, the fuse is not blowing with the fan unhooked.

Thanks for the help

Aslan
aslannm AT yahoo.com.au

Bummer ...my multimeter is rated for a max of 10A only. So I can't measure the amps.

I've taken off the fuse for the auxiliary cooling fan and now the fan is permanently disabled. Its fuse was getting so hot, I can't even touch it for more than 2 seconds. So far the brick is doing fine with a non-functioning cooling fan.

However I observed the relay for the fan (left bottom corner of relay panel) is still hot WITH the cooling fan disconnected. I've swapped in a new relay, not as hot but definitely warmer than the fuel pump relay. Unintentionally I also discovered the cooling fan relay also controls the power windows. All the power windows are fine though.

Any ideas anyone? Is it normal for this relay to be on the warm to hot side?

Thanks

Did you check the radiator switch with your ohmmeter - make sure it isn't stuck "On"

The fan relay is involved with
Turn signals
Air Conditioning/ ACC
Seatbelt reminder
Power windows
Electric Cooling Fan
Heater fan
Electric heated front seats
Hot Start valve

Fuse 7 is only for the elec heater fan- unhook the elec heater fan and pull fuse 7
and measure with your 10 Amp meter from each side of the empty fuse socket
with the ignition switch on. (Check you have +12VDC at one side of that fuse socket)
There should be no current at all since the fan is in series to ground.

Did you replace that relay with one from a junker? maybe both relays are tired?
If the relay gets hot with fuse 7 pulled, then it's likely some cold solder or loose joint in the relay
you can pop the case and look over the relay for any signs of heat, look for bad solder joints.
reflow suspicious joints with a solder iron.

My rad switch is reading infinite ohms.

It appears my fan relay is different from yours. I've removed it and the turn signals, seat belt warning, heater fan are working without it.

On my 89 740 fuse 7 is only for the cooling fan. It is fuse 16 which controls the heater (blower) fan.

There is no current through fuse 7 with the ignition on. I don't dare measure the current at it with the engine on. I have fried an ammeter once so I don't fancy frying another one. Current meter is fused up to 2.5A. 10A socket is unfused. I'm thinking of putting in the lowest fuse in fuse 7 (15A perhaps or maybe 10A if I can find one) and see if that trips with the engine and cooling fan on. I figure a blown fuse or two is better than a cooked ammeter? If the cooling fan can run with 15 or 10A fuse then maybe I'll test it using my ammeter.

I did not replace the relay with a used one. Since the original relay was almost 19 years old, I thought I might as well replace it with a brand new one.

Thanks for help so far.

Thats weird that the relay gets hot with the fan unhooked.
Try your 10 amp meter on the fuse with the fan unhooked.
Cross your fingers that you dont cook the meter. see if there's
current flowing via fuse 7 with no fan. shouldn't be any current.
unless there's a fault in the harness or switch.

Hi,


Thirty amps is quite a bit of current, in fact, an electric clothes dryer should use less then thirty amps at all times.

Remember that heat is caused by resistance to electricity. If your connector has any filth or is even slightly loose, at thirty amps, this equals FIRE. Your gentleman of genius that wired up your chariot of contentment may have unleashed an unbridled force that must be corralled correctly without delay.

You should dismantle the circuit completely, and ascertain if there is worn insulation at any point along the harness. The fan itself may be the crux of the calamity and should be tested for shorted windings. Use a known good fan as a reference of resistance.


Goatman

Hi Goatman,

Thats the idea of checking for current with the fan disconnected.
There shouldn't be current flowing.
This can confirm/eliminate a harness/wiring issue.

Bill

Does your cooling fan even work? Lots of them rust frozen. Jumper the sensor at the top of the radiator, see if the fan even works.
--
Post Back. That's whats makes this forum work.

Oh .. it works. That was one of the first thing I checked. Strangely enough on mine, it is permanently on- irrespective whether the AC is on or off. The PO must have modified it.

How much current is the fan drawing?
You could try measuring at the empty Fuse 7 socket

I will try measuring the current. How much amp is acceptable? And if too high what does it mean?

Looking at the fuse sticker, the fan fuse should be 25A. However now it has been changed to a 30A fuse by someone.

Find an appropriate ammeter, one that does =<30A.
find out how much current is flowing at fuse 7

It should draw less than the original fuse.
Perhaps there's a bind in the motor bushings and it's just
drawing too much current and you need a new fan motor.

Ach! the brickboard dumped the "greater than" symbol.

Be sure to start with an ammeter that does at least 30 amps
so you don't cook your 10A or 20A multi-meter (ammeter).

Well, thats probably why its overheating the fuse area running all the time. Not designed for that. Earlier yrs, it only came on per the sensor/rad temp. Not sure what yr it changed to come on with the sensor/rad and whenever the a/c was turned on.
--
Post Back. That's whats makes this forum work.

As the brushes wear down the fan current increases. This is one way the relay can get hot but it also shouldn't be on all the time. As you said the PO may have done this for a reason. Try disconnecting the fan and see if the engine gets too hot. Maybe the belt driven fan clutch is bad or the radiator may be dirty. Thermostats tend to come apart and maybe there's a coolant flow blockage?

fixit2003

The fan comes on when the AC is on. Not sure if it's supposed to be on all the time when the AC on. But then again, my AC is on 100% of the time (we have a pretty hot weather here)

I've disabled the fan. No ill-effects on the engine temp. Only thing is that the AC is not as cold. I can only guess either the fan was designed on my 89 to be on with the AC OR the PO modified it to be on all the time to get maximum AC output.

The fan is original BTW so maybe the brushes are worn. How can one check these brushes?

Thanks

If the circuit is properly designed the relay will be able to handle the increased current until the fan quits due to brush wear or goes up in smoke as the one in my 850 did. If it's not the relay may overheat and burn the contacts. Had a Plymouth Voyager that started welding the fan relay contacts together and it wouldn't shut off until you rapped on the relay. Just one of the many examples of why Chrysler isn't doing too well.