How do I install switch to turn on Cooling Fans

How do I install switch to turn on Cooling Fans

My 99 3.8 engine still runs very hot in stop and go traffic I know that the cooling fans are not coming on until the temp is between the mid point and the hot. I did change the cooling temp switch with no change. I was thinking if I install a manual switch were I can turn on the cooling fans that should solve my problem. Question how can I install a manual switch to turn on those cooling fans

Look at the fans and see if they are 12V -if they are you need a 12V switch that can carry the current for both fans (12V, 2Amp (make the amperage about double what you actually need) etc).

If the fans are not 12V -you need to transform the voltage to what you need and then find a switch that is at least the voltage and amperage you need.

AC switches can work but the amperage is typically very low. =not useful.

You could use a 3way switch and have
#1 = one fan on
#2 (middle) off
#3 both on

This may not be a problem, the fans are programmed to turn on at 222 degrees, have you confirmed this operation?

The fans kick on when the PCM sees a certain temperature and then grounds a certain wire coming from the fan relays.

You can manually ground this wire with a switch, but you have to figure out which one it is. This would require a Factory Service Manual specific to your year, either that or a lucky guess.

Also there are about 3 relays, and Im not sure which one controls which fan..so its a crapshoot without the right documentation.

Also, if the PCM sees the fans running when the temperature is too low, aka youve switched them on manually, it has been known to throw a code, which will illuminate your SES light.

I was hopping that some has already done the manual switch solution. I did not want to mess around by grouding this wire and that wire just in case I blow something. I think I will visit the bone yard and look for a fan that will fit in front of the rad and tinker with that.

Years ago I put an electric fan in my old 83 Merc Capri. Canadian tire back then in the early 90's sold a kit that had a sensor that mounted to the rad and a relay and wiring that hooked into the fan / power source to turn on the fan when required. You may check that out.

Since you have the 3.8, you might consider this as a plug and play solution:

http://www.intense-racing.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=CFC-062&Category_Code=CS&Product_Count=6

I DO NOT know if this will work with an Intrigue or not, Ive never seen an Intrigue with one. But the 98-99 Intrigue shouldnt be set up that much differently than the GP,Impala,Regal, etc of the same vintage, which that kit fits.

There are ways to do it manually. Im just not entirely sure how to do it, but its done quite often to H-bodies, and Im sure the W-body guys have done it elsewhere.

Since you have the 3.8, you might consider this as a plug and play solution:

http://www.intense-racing.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=CFC-062&Category_Code=CS&Product_Count=6

I DO NOT know if this will work with an Intrigue or not, Ive never seen an Intrigue with one. But the 98-99 Intrigue shouldnt be set up that much differently than the GP,Impala,Regal, etc of the same vintage, which that kit fits.

There are ways to do it manually. Im just not entirely sure how to do it, but its done quite often to H-bodies, and Im sure the W-body guys have done it elsewhere.


Thank you for the info, It seems a bit pricey but it sure looks like a nice pro solution.

Yeah it is pretty expensive, several places sell them, so you may find one cheaper.

But like I said, I do not know if it will work with the Intrigue, and I dont think youll find a single site that will claim it will, nor will back you up if it doesnt, so there is a risk of it not working.

Rolm,

If you are good at wiring yourself, you can probably just make a harness up yourself and save yourself $100. It looks like there are 3 standard automotive relays, I am not sure why because I thought there were only 2 fans on our intrigues, but anyway, you can pick them up and probably some wiring with the plugs on it from a wrecking yard. Go to radio shack and pick up a lighted switch if you wish and install it all in probably a half day or less.

I'm not sure if this will help you at all, but if you turn your AC on, the fans will come on as well. They come on because the condensor is mounted in front of the rad.

I can't belive it I posted a wanted Ad in craigs list for the switch and a guy is willing to sell me one for $25 I will let you guys know how it is working. The down side my heater core blew for the 2 nd time

Perhaps that is why the heater core blew, because of your excess heat. I know it has been hot around here the last few weeks, that and excessive Toronto heat and sitting in traffic could have possibly weakened your heater core. I don't blame you for installing the override switch.

By the way, I was looking at my intrigue the other day and why can't you just put a jumper switch to your fan relay to make it come on? Just go to Canadian tire and get a switch and some wire.

On some cars, turning on the A/C triggers the fans to come on at a lower temperature. I had a 1991 Dodge Spirit that would always run hot in stop and go city driving in the Summer unless the A/C was on.

You might want to get a grill thermostat and place it on the engine and see what temperature it reads when the fans turn on. Maybe the gauge on the dash is giving you a wrong reading.

You might want to get a grill thermostat and place it on the engine and see what temperature it reads when the fans turn on. Maybe the gauge on the dash is giving you a wrong reading.


A more accurate option would be to get a scantool and see what temperature the PCM is actually seeing from the sensor.

I just picked up the over-ride harness to-day and it looks like it is plug and play I will install the switch in a few days and give an update

I installed the hi low fan harness and it works like a charm. On the low side the fans run very slow and quite on the high side the fans come to life and blow like crazy. I can't see me having cooling problems from this point on. I also think I found my over-heating problem the dam cooling fans never came on. on high speed, there must be a swithch or a relay that died a long time ago. I will bet that was the problem all along, My money is that the other guys that were having overheating problems may have lost their high speed fuse or relay. Can anyone tell me were the high speed fuse or relay is I am curious at this point even though I fixed the overheating in a manual way. late

Rolm,

I am glad that the by pass worked well for you, but am amazed that the fans run at two speeds. I have never heard of that, but am glad that I know that. I will monitor my system to see how it works. Unfortunately, the summer is almost gone now and we will probably not need any high speed fans in the near future.

I just have to try to figure out what to do with my vacuum cleaner in the front end of my Intrigue now. The AIR pump. Ach!

I'd like to know where that high speed fuse/switch/relay is as well.

Rolm,

I am glad that the by pass worked well for you, but am amazed that the fans run at two speeds. I have never heard of that, but am glad that I know that. I will monitor my system to see how it works. Unfortunately, the summer is almost gone now and we will probably not need any high speed fans in the near future.

I just have to try to figure out what to do with my vacuum cleaner in the front end of my Intrigue now. The AIR pump. Ach!

I'd like to know where that high speed fuse/switch/relay is as well.

You can try this: start your engine and turn on you A/C and open the hood and let us know if the fans are running on Hi or very low, my fans run very slow to a point were you can't hear them run.

Well guys here in Toronto today is was quite hot and yes I did get stuck in traffic for abought 20 minutes. No problem I turned on my cooling fans and presto the temp stayed just below the 1/2 way point. The manual switch works great. On spec I found the cooling fan relays I will start replacing one at a time and see if I can solve the over-heating problem and post the results in the hopes of helping others out with over-heating problems. later

If you can get ahold of a Factory Service Manual it would probably tell which relay controls what. It seems like there was someone here who had one at some point.

Hot in Toronto! Ha, We had frost last night in Niagara! Glad to hear your bypass works. If you find the relays let me know. That is a good thing to know.

If it helps -- here's what my 2000 Intrigue shop manual schematic (pg 6-380) shows. Two fuses and three relays are involved in this, all in the "underhood accessory wiring junction block" (fuse box on right tower). Slow fan speed is done with cool fan relay 1 activated by the PCM, with power supplied by the cool fan 1 (40amp) fuse. This feeds 12VDC through the relay to the two fans in series (6V each); thus the slower fan RPM. For high speed, the PCM activates cool fan relay 2 and cool fan relay 3 simultaneously. Cool fan relay 1 remains activated to continue providing 12V to fan motor #1 (RH). Cool fan relay 2 grounds fan motor #1 (RH), so it gets the full 12V instead of 6V. Cool fan relay 3 provides 12V to fan motor #2 (LH), already (permanently) grounded, through cool fan 2 (30A) fuse. Just for the record, I checked my fuse box, and find both fuses are 25A, not 40 and 30 as the schematic indicates.

Your service manual should also say this...

The PCM commands Low Speed Fans ON under the following conditions:

The engine coolant temperature exceeds approximately 106°C (223°F).
The A/C refrigerant pressure exceeds 1310 kPa (190 psi).
The vehicle is shut off when the engine coolant temperature is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:

The engine coolant temperature reaches 110°C (230°F).
The A/C refrigerant pressure exceeds 1655 kPa (240 psi).
Or When certain DTCs set.

glad to hear you got the fan switch working Rolm !

Ok with the above info what would be causing my over-heating problem. So if you were to guess which relay should I replace. All the fuse are ok, relays are tough to check. As I said I will go to the bone yard and pull out the 3 relays and replace one at a time. I have one question should the PCM be re-flashed every few years.

I finally fixed my over-heating problem even though it was in a round abought way, see links above for the manual harness I bought on Craig’s list. I set the cooling fans to run all the time on low speed and that keeps my engine temp at the exact tem that the thermostat is designed for just under the half-way point. Bottom line all the other guys that had over heating problems had the same issue as I. The dam fans did not come on soon enough I would have to assume that the computer was lazy or it did not turn on the fans when it should have. Can any one fix the problem the proper way and not the way I did it in a round abought way.