pacallen

Recently my Legend has been getting hot during prolonged stops, but only about once a week at the most (and never gets to redline). The car heats up and there's no air going over the radiator because the car is stopped and the fans aren't coming on correctly. I watched the fans today with the car parked and at normal operating temperature, and both the radiator and condenser fans simultaneously kicked on periodically and the temp stayed within normal range. What are the likely culprits since the problem is so intermittent?

I was looking through the wiring diagrams and the troubleshooting flow chart and I would guess its most likely a faulty fan control unit, but the manual doesn't give any tests to determine if its faulty (and it would probably test fine anyway since I can't seem to replicate the problem now). The reason I'm leaning towards a relay is because the problem seems to be the worst on hot days and I would guess that the soldered connections expand and break much like those on the main relay (and I still don't have a/c so the interior gets pretty toasty). I would have thought if the problem was a coolant temp switch problem that it wouldn't be intermittent. Do I have any options besides systematically replacing relays and switches until the problem goes away (which is hard to tell too because it's so intermittent)?

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SOLD: '87 Auto Sedan (12/31/2003)

 

awelliott

What you've said sounds logical. I think shotgunning spare parts is your only shot unless you want to wait for the problem to become more solid. It shouldn't be too expensive to swap the relays and FCU if you have a boneyard nearby. Another possibility is that your radiator is starting to get a little tired (clogged), and its cooling capacity is a little diminished.

KAHruzer

I'll save you some time and parts. I had exactly your symptoms, except I do have a working A/C system. I've gone through everything related to the cooling system, testing or replacing each component and found the issue to be the Coolant Temperature Switch on the radiator. Fans back to normal now.

My Rad Fan was not coming ON unless the A/C system forced both fans to run, so it would cycle them both ON/OFF per the A/C input. But, the Rad Fan would never come ON by itself, even once gauge was well warmed up.

The only clue I had that something was wrong was it'd tend to pop the needle up at idle during long stops. I knew it wasn't the coolant or clogs since I have recently completely redone all that including a flush and thermostat.

The temp switch cured it all. I was fairly certain when I began the Fan Control Unit had gone bad, but changed to another and problem stayed.

Anyway, I think there's a test for the switch, but I didn't do that one at the time since, of course, it was the last piece, and least suspected.

Kind of expensive part, too. I tried to get one at my local parts store and their books gave me the wrong one twice (two different ones), one flat didn't fit (different screw size) and the other one had different orientation for the poles and the key. Be sure to get a matching one in those respects. Also, in testing the one, it didn't match our specs for resistance measuremnts. Forget offhand what they're supposed to be, but it's in the manual for the test.

I ended up going to my dealer, who also was out of stock, but one prominent mechanic there had one in his 'private stash', whatever that meant. I paid about $50 for the thing. It was around $40 for those incorrect ones, though, so it's going to be around that.

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Stock 1987 Legend LS Coupe 180k (11/07)

pacallen

Those symptoms sound exactly the same... I don't have the manual accessible atm but do I need to drain the radiator to remove the coolant temperature sensor? If so I'll run and pick up some Honda coolant on my way back home. What brands of aftermarket sensors did you try? I've always had great luck with aftermarket parts, especially as it gets harder and harder to get certain things from the dealer. Otherwise I guess its off to the junkyard to find a working one.

I may take out my FCU anyway to resolder things to help rule it out. I wouldn't think my radiator is clogged because I do regular flushes and recently changed out all the coolant hoses. Water pump is getting on a bit (5 years, ~40,000mi) and was done when I bought the car and had the timing belt replaced.

Thanks for replies all.

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SOLD: '87 Auto Sedan (12/31/2003)

KAHruzer

You can drain it first, in a nice controlled manner, or just pull the switch at which time it will drain itself, all over you as you try to get the thing unthreaded. (It's right next to the drain valve).

Take your old one with you to the parts store. Get a match on the key and orientation and screw size and it should probably work, though, as I stated, the one I did test didn't have the same specs for the switching action. That's what made me go to the dealer. When I put it in water on the stove and raised the temp, it was way out from what the manual said. But, that one was the correct screw size with an improper key orientation, so maybe it was supposed to be different.

Those were both Borg-Warner brand.
Those folks know what they're doing, but they did sell off the sensor group to another outfit awhile back. Still carries B-W logo, however.

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Stock 1987 Legend LS Coupe 180k (11/07)

BUSINESSMAN07

when's the last time you've had your water pump replaced?

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pacallen

5 years, 40k miles, installed by the dealer w/ the timing belt, tensioner, etc.

I'm going to try an aftermarket sensor next week. It really isn't a big deal since it never fully overheats and only gets close when I'm stuck in heavy traffic (esp. w/ stop and go vs just stopped and idling). I think I'll hit up a junkyard for a comparison piece as I can't go w/o my Legend running atm.

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SOLD: '87 Auto Sedan (12/31/2003)

KAHruzer

Here's the Coolant Temperature Switch, along with the bag the new one came inside.

Note the orientation of the electrical connection, and the key.
Apparently, that's what makes it the right spec.

I put that part number into Google and came up with this:
ACURA LEGEND RADIATOR FAN CONTROL SENSOR ASSY. @ AcuraOEMparts.com - Acura Parts from Delray Acura


....only $30.66

Attached Images

 

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Stock 1987 Legend LS Coupe 180k (11/07)

pacallen

Thank you for posting that pic KAHRuzer! According to Acura's Ownerlink eStore that part is still in stock. Another site says that part was shared between the G1/G2, 91-05 NSX, and 96-04 RL so they shouldn't be running out any time soon. It's listed as "SENSOR ASSY., RADIATOR FAN CONTROL" and fits in the bottom of the radiator so I assume it's the right one... Only $31.11 on a discount OEM site too.

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SOLD: '87 Auto Sedan (12/31/2003)

KAHruzer

You see why I avoid using my local dealer whenever possible?

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Stock 1987 Legend LS Coupe 180k (11/07)

pnoye2

I've been very lucky (knock on wood) with my engine cooling system components ...I religiously clean every single one of them on a yearly basis.

+1 on the thermosensor btw!

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294K+ miles; original power/drive trains

SilentBob

I think this is the same problem I have been having.
What do I need to remove to get to the coolant temperature sensor?
Any Diy?

KAHruzer

DIY:

1.) Drain Coolant from Radiator (hold for refill if good)
2.) Disconnect Electrical Connection
3.) Remove Coolant Temp Switch (27mm box wrench or deep socket)
4.) Reverse Order to reinstall

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Stock 1987 Legend LS Coupe 180k (11/07)

!OREO!

This may seem like a dumb question but where is this switch located. Im new to these cars so if someone could explain so I understand.

Nevada Ray

It's part #27 in the diagram below...