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Thread: Solution to cooling fan resister failure??? Reply to Thread
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Topic Review (Newest First)
03-12-2013 06:55 AM
amc49 I ended up rebuilding the resistor minus the thermal fuse. The fuse seems stupid if the thing STILL melts into plastic slag, as mine did. I used much bigger spade connectors and positively drilled through them to use small screws/nuts to bolt them together, used bigger wire too. The whole thing works great and I just watch the connector more now. Cost maybe $10.
03-12-2013 06:04 AM
whynotthinkwhynot The temperature sensor is located in the center of the cylinder head between cyl 2 and 3. It is the same sensor that shows your engine temp.
03-12-2013 05:24 AM
239rsw Now that the weather is getting warmer, I am planning to look into the cooling issue that I have had. I've replaced the thermal fuse (resistor) a few years ago. It worked (no overheating) until the weather got really warm. The following spring, I replaced the resistor assembly from dealer and it failed again.
Looking at the schematic diagram, if my connectors were bad, the fan should still not work if resistor was replaced. I am wondering if the sensor, if any, that kicks off the high-speed relay is not working. Where can I find that sensor?

I have an 02 zetec
08-12-2012 11:51 PM
amc49 a_2000_se and others are right. I am so stupid, the lower section of the schematic is only rated at 30 amp, if you simply tie the resistor wires together to bypass and full fan speed, you will have too much amp flowing through the wires.

Looking at this much later caught it, my bad. looks like I'm fixing to experience it first hand, mine started overheat at idle only today. Will be yanking that resistor tomorrow.

Going up underneath the fusebox may not be much of an option, there's a godawful bunch of wires under there and not a lot of room without disconnecting more stuff. I rebuilt one of those entire boxes when mine was shattered in accident. Bought just the plastic box for $10 after cutting out all the wiring in junkyard, the guy at part desk thought I was crazy. The fusebox is part of the main wiring harness. It took maybe 2 hours to rebuild it but I saved a bunch of money doing so.
05-12-2012 07:29 PM
hanojreason Winterbeater!!! Thanks so much! Worked like a charm for me!
04-22-2012 01:48 PM
whynotthinkwhynot Good solution. The same thing can be done underneath the box by simply jointing or bridging the hot wires to the relay coils. Then you don't have relays jammed in there on top of wires.

At least you didn't wire it constant hot like some people do. Then they wonder why their fans and alternators keep blowing up.
04-22-2012 01:38 PM
winterbeater
Repair for blown thermal resistor

Fixed it by jumping the relays as suggested. Soldering the thermal fuse was a pain, so I took the shortcut. Works great so far. Fans come on full power at 107C.


First picture shows the low and high speed fan relays at the bottom right. Pull the relays out. This is the fuse box right under the hood.



Insert a jumper wire as shown. Re-insert the relays. That's it! The PCM then activates the high speed fan circuit when it signals the low speed relay.
04-13-2012 09:49 AM
winterbeater
Quote:
Originally Posted by emsvitil View Post
Even cheaper is to bypass the thermal fuse with a piece of wire..........
Agreed, but then you run the risk of wiring or connector meltdown. When I worked in HVAC warranty, I saw blower motor resistors that had overheated, where the thermal fuse failed to melt that actually caused fires, or more often wire meltdown.
04-13-2012 02:37 AM
emsvitil
Quote:
Originally Posted by winterbeater View Post
New approach on this issue. I'm just a cheapskate. That's why I bought this old Focus for $2G and patching it up ever since.

I pulled the resistor. Ohmmeter tells me that only the thermal fuse is blown. NAXJA forum (one of my other beaters) dudes have fixed heater fan resistors with Radio Shack thermal fuses for $1.79. That's my next step. I'll try to do pictures.
Even cheaper is to bypass the thermal fuse with a piece of wire..........
04-13-2012 12:23 AM
Magus2727 funny to see a fellow XJ owner who also has a Foci on here. funny... wiring up the low speed fan relay to turn on the high speed relay would be the cheapest fix as it would only require a small gauge wire to the +12V coil on the high speed fan relay. most likely you have the 12" or less of 16 AWG wire laying around to do this...
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