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Courtesy of member "John"

968CoolingSysDiagTests0210.pdf Size: 696.39 KB  Downloads: 473

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[DaveN]

Tks, Flash. Just found all the bits in the electrical diagram and was logging in to the do the search that so many people fail to do-one step ahead as usual [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img] Now go retire already, see you at X-mas.

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[flash]

lol - can't retire until the SC kits are out the door

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[DaveN]

Just an update, what a wonderful document for the cooling system! Docs like that could put mechanics out of business [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]
Looks like the rad temp sensor is toast. The only good part of this experience is that my neighbour had a 30mm socket to remove the switch as I don't have anything that big - yet. Parts on the way so hopefully a happy ending.

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[blue968]

Be VERY careful replacing the sensor, One think it would need to be pretty tight well let me tell you. If you tighten it to much it will crack the plastic housing and have a slow leak. Ask me how I know this [img]style_emoticons/<#EMO_DIR#>/mad.gif[/img]

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[flash]

i think blue is talking about the fan temp switch, and cracking the plastic side tank of the radiator - the sender is brass and goes into the aluminum block

another thing to remember when testing the resistors, is to factor in the resistance of your meter (touch the probes together for a reading) - mine is about .6, so the reading at the resistor is 1.2

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[DaveN]

Yea, I'm at the rad and it's a brass housing so we are ok. Bit of a panic though as I'm signed up for a fun run on a very long and windy road Sat and they can't drop ship the part so I have to deal with the mail to my mechanic and then from him to me [img]style_emoticons/<#EMO_DIR#>/unsure.gif[/img]

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[blue968]

HI Dave,

I'm confused, were your temperature switch/sensor goes into the radiator, is it all brass? Mine was a brass sensor that screwed into an aluminum block as Flash described. The problem is that when you screw the sensor into the aluminum it makes a seal around the plastic tank and if you over tighten it will crack the plastic tank, I have a slight hairline crack barely even noticeable but it weeps out. Good news is my car is running much cooler now. I tried to describe the issue as best I can but I hope this helps and you save your radiator.

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[flash]

just so we all have the terms right:

the sender goes into the engine which is aluminum - this sends the signal to the computer

the fan switch goes into the radiator - it is not a sender - it just closes a circuit at particular temps

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[DaveN]

"the fan switch goes into the radiator - it is not a sender - it just closes a circuit at particular temps "

Yes this is my issue, new on on the way and will be carefull not to torque it with my 2' extention bar [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

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[flash]

lol - yeah - that one freaks me out every time too - i just changed mine AGAIN - i keep waiting to crack the tank

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[blue968]

Sorry if I confused things but I was referring to the switch as you mentioned, thanks for the clarification on that flash.
So Dave definitely don't use that 2' extension bar LOL or you will looking for a radiator with me LOL.

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[flash]

no worries - just thinking about who else might be reading this years down the road

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[Rudolf968]

I had a similar problem, the fans didn't stop after a "hot" ride. I changed the fan switch at the radiator, but no cure. It was the relay, its a pricey relais with a double circuit because of the 2 fan-speeds.

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[jg968]

John,



Thanks a ton for this excellent write-up! It helped me diagnose and fix an issue with my radiator cooling fans. When I purchased the car I noticed that as soon as the car got warm the cooling fans were cycling between high and low speed continuously. 11 sec high-speed on, 3 sec high-speed off, repeating this pattern. When I talked to a past mechanic friend of mine (who lives in a different city) his first thought was I had a one bad fan motor and that the other was having to compensate. Turns out, his gut diagnosis was pretty accurate.



Using your diagnostics I was able to tell a) both fans worked, <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" /> I had no shorts in the system, c) I had an open in the driver side fan speed resistor. My mechanic friend said that the resistors are a trouble area in terms of corrosion and that I should take a look. This is where it gets interesting. First, after taking the cowl cover off, I found an old mouse nest right next to the heater fan motors (car was stored in the winters in Nebraska. Hint - its good to take things apart once in a while :-) I did a thorough cleaning of the entire area). Most importantly, I found a disconnected speed resistor! No corrosion, just a blase connector that was disconnected. Talk about a simple fix.



Now I'm wondering why it was disconnected.I doubt it could have vibrated loose. I'm thinking someone must have disconnected it intentionally. The car did spend some time in Phoenix (previous owner). Would someone try to force the fans to run high speed in a hot climate? Any ideas anyone?



JerryG

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[flash]

i suppose they may have tried that - there are definitely better way around the problems there



too funny about the mouse - we have seen a number of critters camped out in stored cars - it's always amusing to find them



the resistors are known to corrode and even to fail - if the resistor doesn't work, the good news is that they are quite inexpensive and easy to change out

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[pinball1008]

Having gone through the diagnostics, it looks like my rad temperature sensor has gone.

I had a heck of a job getting the wires off due to the limited access and big hands.

What's the best way to improve the access, remove the top hose or go from underneath the car?

The batwing (front apron) has to come off anyway as I've a shiny new splitter on it's way to the UK.

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[flash]

that one is a real bugger. going in from underneath leaves little wrist room. removing the upper hose works, but the stub of the port is still in the way.



regardless, if you have the radiator fans in the car, you will need a deep socket to remove and install it (i think it's something like 30mm). the only way i have found to do it with a wrench is to remove the fan assembly.

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[pinball1008]

Thanks Flash, a little more work than I wanted, but nevermind.

I'll get the new part, then at least I can make sure I've got the right socket.

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[flash]

the fans come out pretty easily. 2 plugs, 6 screws, and a little grunting and groaning as you figure out the angle for removal.

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