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1990 164QV Euro spec & 1991 168B
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164 Cooling Fan Circuit Testing 101

This write up based on 1991-95 12v/24v USA models other "Euro" models may not have two speed fan, same wiring; etc.
164 Cooling Fan Circuit Testing Part A

A. Cooling Fan Motor Power Circuit Test

The power circuit consists of the following components - Battery power circuit block terminal and 40A fuse bar on false firewall, red wiring to cooling fan motor, fan motor, and brown wiring from motor to pin 30 on low and high speed relays and to resistor.

A1. First off always look at and feel with your fingers the cooling fan motor 40A fuse bar on front of false firewall near brake fluid reservoir cap for evidence of burning or a hidden hairline crack. This fuse has 12v power at all times straight from battery.

Replace bad fuse bar with 40 to 45 amp fuse bar ( I use 40A Alfa 164 fuse bar or Honda 45A one).

A2. Next with ignition key OFF for SAFETY test cooling fan motor to see if the fan blade will turn freely by hand (be careful as edges of blade very sharp).

Remove, repair or replace motor if binding or frozen (Remember fan blade nut is L/H threads so righty loosey to get it off). I rebuild the old motors with new bearings, machine armatures if needed and replace bad carbon brushes.

A3. Then, the quickest way to test the cooling fan motor POWER system without any fancy test equipment is to locate brown and blue 2-wire connector or the two wires to fan resistor in top corner of cooling fan shroud. This is hidden behind relay mounting bracket that is bolted to radiator top support.

A4. Disconnect the 2-wire connector or if just brown and blue wires attached separately to resistor connector disconnect both wires (brown wire comes from high speed fan relay's fan motor terminal). Ground brown wire to chassis and see if fan runs. If wire tip sparks when you touch wire to chassis and fan runs then 40 amp fuse bar on false firewall, wiring and fan motor are good.

A5. If motor does not work and no spark when you touch wire then either the fuse bar on false firewall is blown/cracked (inspect it for hairline crack) or red and brown wire connector at fan motor or motor are bad.

A6. Replace bad fuse bar with 40 to 45 amp fuse bar ( I use 40A Alfa 164 fuse bar or Honda 45A one).

A7. Repair red and brown wire connector at motor if burnt.

A8. Repair or replace motor if bad (fan blade nut is L/H threads so righty loosey to get it off). I rebuild the old motors with new bearings, machine armatures if needed and replace bad carbon brushes.

B. Cooling Fan Motor Control Circuit Test

The control circuit consists of following components - ignition switch, the two relays energizing fuse in main fuse box, two 50A relays near radiator, resistor in radiator shroud, thermal switch in radiator and trinary switch on A/C reciver dryer.

B1. There are a couple ways to quickly verify control circuit is working. First ignition switch must be in on position.

B2. One way with key on and hood opened is to remove plastic cover behind false firewall and locate A/C trinary switch on black receiver dryer cylinder. Now locate white connector with thin brown and black wires.
Black and brown wires are ground wires for low speed relay energizing coil. Jump two wires together with a paper clip or whatever metallic you have handy.

Now the Low Speed relay near radiator should click and if low speed resistor is good and fan power circuit fuse and wiring good fan should run on low speed.

Note: Wires in red connector also at receiver dryer are for a/c compressor clutch relay.

B3. Second way to verify both low and high speed relay circuits are working is to locate wiring connectors to radiator thermal switch. On 12v models thermal switch and wiring located in side of radiator closest to air cleaner. Gain access to thermal switch and wiring by removing plastic panel between a/c condensor and headlight in front of air cleaner.

Note: on 24v models radiator thermal switch located in side of radiator close to front of engine and wires come over the top of radiator to same connectors as 12v models in front of air cleaner area. If wiring stock factory set up there will be two connectors- one with two small brown and black ground wires hooked to white and black wires for thermal switch and one small brown-white wire hooked to red wire to thermal switch.

Again with key on disconnect wires and jump black to brown with paper clip and low speed relay near radiator should click on and if fuse in fuse box, low speed resistor good, etc., etc., fan should run on low speed.

Now jump brown-white wire connector to black wire and high speed relay near radiator should click and fan should run on high speed.

B4. If with key on relays don't click when small brown and small brown white wires grounded to black wire or to chassis check fuse in main fuse box under dash for power.

B5. Testing Low Speed Resistor If with key on low speed relay clicks but fan does not run and high speed relay does click and fan runs then low speed resistor is bad or blue and brown wire connectors to it are bad or disconnected.

Locate blue and brown wires going to resistor which is located in top of radiator shroud and hidden behind relay mounting bracket on top of radiator. Disconnect wires from resistor connector and jump wires together and test low speed relay circuit again and see if fan now runs on high speed. If resistor bad jump wires together for the summer and replace resistor before the winter.
 

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Excellent write-up, as usual!

Readers outside the USA may like to note that all four 164s I've owned have/have had a single-speed fan with no resistor. Radiator switch has two push-on terminals; one has a brown wire, the other a black wire. Testing is a simple matter of connecting the two terminals with a paper clip. Ignition must be ON for fan to run.

Relay is in group behind left headlight, the most outboard (furthest left) of the three - where 'left' means from a seated position in the driver's seat.

Fan switches are available in different temperatures; my ex-Singapore 164 had a 75-degrees C switch, which was ludicrously low once I had replaced the thermostat with a 90-degree unit; the fan ran almost all the time. I think ideally for temperate climates, the thermostat should open at 87 degrees and the fan should come on at 95 degrees. My '91 164 is somewhere near this (engine stays at 80 degrees C, fan rarely comes on), but has the amusing fault that the fan is off-balance. I feel a strange shudder in the car when the fan starts and stops in heavy traffic after a run (Auckland motorway). I haven't bothered to fix it, because it is quite nice to know that the fan works :)

If ordering a replacement switch, first check that you don't already have any suitable candidates on hand from other Italian cars. I ordered one once at a significant price, and when it turned up I was annoyed to realise I already had five functionally-identical and same-thread-size switches lying around in FIAT radiators aged from 1970 through to 1989. Some FIATs of the 80s have two-speed fans, too.

EDIT: In checking this post, I actually went and did that test with the paperclip to my '89 164 - the relay clicked, but my fan does not run! That, combined with the sticky temperature gauge (the needle sticks at half-way) is a disaster waiting to happen when the summer eventually gets here. Even though the thermostat is practically stuck-open on this particular car, give any car long enough stationary running and it will overheat. Something on my to-fix list, then... and this is something I think should be tested at each 'major' service interval?

I went looking for a 40A bar fuse on the firewall, but didn't find one. See pictures - am I missing something obvious? I have a plastic box with battery cable connections inside - and covers which I removed both inside and outside the firewall. Isn't it amazing (and sometimes frustrating) how many variations there are on these cars?

-Alex
 

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164 Cooling Fan Circuit Testing 101

This write up based on USA models other models maybe not have two speed fan, etc.
I could be losing it today but I don't think that was there 15 minutes ago - apologies if it was, and if not, thanks! ;)

-Alex
 

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Discussion Starter · #4 · (Edited)
I could be losing it today but I don't think that was there 15 minutes ago - apologies if it was, and if not, thanks! ;)

-Alex
Document is a work in progress so new data appears as I edit and since there are some many variations of systems in these 164s it is hard to be correct for all configurations so hence the USA disclaimer.

As for your second picture that is back of false firewall and a/c heater blower motor 40A fuse bar hooked up there on USA models.

The cooling fan 40A fuse bar on front on USA models.
 

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Source for cooling fan elec. connector

Hey, here's a related question:

My cooling fan wasn't working - car cooled OK on the highway, but would overheat in traffic.

I checked the main fuse (OK), and went on to look at the wiring behind the radiator. Noticed that the connectors to the resistor were melted - just crimped on new connectors, and low speed began working.

I did the other debugging described in Alfisto Steve's excellent post (above), and determined that both relays (eg, both HI and LO speeds) will work OK when the wires to the temp switch are connected to ground. I resolved to install a VW lower temp thermal switch, because I still can't figure out why the HI temp/speed circuit didn't switch on when the car overheated.

Then I looked at the 2-wire connector that attaches to the fan motor - that thing is pretty cooked. Locating a fan motor with a plastic connector right next to the exhaust manifold doesn't seem like a great design (if you asK me). My connector is sort of working, but doesn't look that reliable.

So, here's my question: Is the plastic female connector that plugs into the fan motor available? Any suppliers in the States? And, if not, has anyone tried just using two 1/4" female spade lugs?
 

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Discussion Starter · #6 · (Edited)
Hey, here's a related question:

My cooling fan wasn't working - car cooled OK on the highway, but would overheat in traffic.

I checked the main fuse (OK), and went on to look at the wiring behind the radiator. Noticed that the connectors to the resistor were melted - just crimped on new connectors, and low speed began working.

Did the other debugging described in one of the above posts, and determined that both relays (eg, both HI and LO speeds) work OK. Resolved to get a lower temp thermal switch.

Then I looked at the 2-wire connector that attaches to the fan motor - that thing is pretty cooked. Locating the fan motor & wiring right next to the exhaust manifold doesn't seem like a great design (if you as me). This connector sort of works, but doesn't look that reliable.

So, here's my question: Is the plastic female connector that plugs into the fan motor available? In the States? And, if not, has anyone tried just using two 1/4" female spade lugs?
Not the best set up but do you have the factory original insulated aluminum cap bolted to end of fan motor to give it some relief from exhaust manifold heat?

As for connector to motor I do not know of availability. If you do use female spade connectors use yellow size for that gauge of wires.

Also do not revese wires if you do use seperate connectors as fan motor will run backwards (Murphy's Law applies here).
 

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Not the best set up but do you have the factory original insulated aluminum cap bolted to end of fan motor to give it some relief from exhaust manifold heat?

As for connector to motor I do not know of availability. If you do use female spade connectors use yellow size for that gauge of wires.
Steve:

Thanks for the quick reply.

Yes, my motor does have the insulated aluminum cap, which does cover the terminal area. But, it still gets mighty hot in that area.

I probably will try using just plain terminals - yellow gauge, of course.
 

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If you use two spade connectors (I've had a car wired that way) be sure you code them somehow so they can't be reversed. inverting the sex of the lugs would work (one male, one female on each side). The reason is that someone else reported trouble with cruise overheats but all was well in heavy traffic -- very confusing. He ultimately found his fan wired up backward as a pusher fan. It was countering the free air flow in cruise and struggling to get cooling, but was OK at low speed because it could push enough air backward. Not my observations, but a report by someone else. Sounds a bit iffy, but could happen. So ensure no one inverts the plugs somehow.

Michael
 

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Steve

Does your write up , [thank you], apply to the 24V LS and Q?
 

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Discussion Starter · #10 ·
Steve

Does your write up , [thank you], apply to the 24V LS and Q?
Yes it does I even mentioned the one main difference is location of thermal switch in radiators.
 

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I've seen recommendations to have the radiator fan set to run on high whenever the motor was running. Question: What would be the results in winter? Would that keep the motor from reaching a suitable temp to provide adequate heat for passenger compartment? Thanks.
 

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Steve, excellent write up!

I have a spare fuse in the glove box of my 164 just in case of the hairline crack thing happening. What do I ask for at the Honda parts counter when I want to buy a spare?

Is there a problem with the factory plug on the fan motor? Both of my Q's have spade connectors and replacement wire.
 

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Discussion Starter · #13 ·
Steve, excellent write up!

I have a spare fuse in the glove box of my 164 just in case of the hairline crack thing happening. What do I ask for at the Honda parts counter when I want to buy a spare?

Is there a problem with the factory plug on the fan motor? Both of my Q's have spade connectors and replacement wire.
Not usually but if you have a bad connector (high resistance) brown at motor or blue or brown at resistor wiring can get very hot and maybe go to black melt mode. I recently had to cut off bad blue at resistor terminal and replace to cool wiring down and get fan to run correctly on low speed.
 

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Hi guys! Great information, as usual. I'm trying to bench test a spare engine cooling fan. When I hook 12 volts to either one of the spade connectors at the motor, nothing happens...is it me, or is it the fan motor? I was told it works....
VM
 

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Discussion Starter · #15 ·
Hi guys! Great information, as usual. I'm trying to bench test a spare engine cooling fan. When I hook 12 volts to either one of the spade connectors at the motor, nothing happens...is it me, or is it the fan motor? I was told it works....
VM
You need POS post of battery +12v in and other terminal of motor has to be grounded to - Neg post of battery to test cooling fan motor.

It is best to use actual connector from 164 wiring harness if possible.

You can disconnect it from fan motor in car and plug it into motor you are testing and then ground brown wire going to resistor in fan shroud and the spare motor should run.
 

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Hi guys! Great information, as usual. I'm trying to bench test a spare engine cooling fan. When I hook 12 volts to either one of the spade connectors at the motor, nothing happens...is it me, or is it the fan motor? I was told it works....
VM
You did not mention hooking up the ground wire as well. Did you do that? You need to hook up a power source and a ground. The brown will be the ground wire.
Charles
 

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and it a DC motor

that draws several amps of current. Unless your power supply has enough oomph, (ie adequate current capability) the fan wont run at all. You need a 3 to 5 amp power supply (ie you can;t use a 'plug in the wall 12 volt DC converter)
 

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Thanks - I thought 1 connector was for +12 and the other was for plus+12 AFTER having gone through resistor and ground was simply to frame. is this not correct?
VM
 

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nope

12 volts to one lug, ground to the other--
 

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again, please...

You did not mention hooking up the ground wire as well. Did you do that? You need to hook up a power source and a ground. The brown will be the ground wire.
Charles
Do you mean the terminal on the resistor that the brown wire connects to? I did try grounding the battery to several different places on the fan frame
VM
 
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