cooling fans p38 dse.

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big boss

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can anyone help, ive got a 1997 p38 dse and the electric cooling fans are constantly running even when i start it first thing in the morning!! its never had any overheating problems with it. im guessing its an electrical fault???:mad:
 
More than likely a faulty Air-Conditioning pressure switch.

Can you turn them off by presssing the 'aircon off' button?

With the petrol model I would suspect a faulty engine coolant temp switch but it appears that the Diesel model doesn't use the aircon fans this way :confused:
 
big boss said:
can anyone help, ive got a 1997 p38 dse and the electric cooling fans are constantly running even when i start it first thing in the morning!! its never had any overheating problems with it. im guessing its an electrical fault???:mad:
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There are 2 switches involved on the diesel that work on aircon system pressure plus several relays
 
SpudH said:
More than likely a faulty Air-Conditioning pressure switch.

Can you turn them off by presssing the 'aircon off' button?

With the petrol model I would suspect a faulty engine coolant temp switch but it appears that the Diesel model doesn't use the aircon fans this way :confused:
Click to expand...
Exactly. The diesel only turns the fans on if the AC press goes too high(=hot). Either a faulty pressure switch or faulty wiring. IIRC, the switch goes to ground. There are 2 pressure switches on the AC line under the left headlight - one is high/low press for the compressor and the other for the fan. Unplug both and the AC won't work but you'll see if that's your prob (sounds somewhat unlikely, tho, I've never heard of a switch suddenly sticking on - just not working anymore). You'll need to check what's causing the relays to energize.

The guy with the temp switch on the side of the radiator is thinking of a 1978 VW Golf. Was this an honest mistake or just passing a brain fart? Or is the thought of people with this problem searching all over their radiators for nonexistent temp switches funny?
 
SteveMFr said:
The guy with the temp switch on the side of the radiator is thinking of a 1978 VW Golf. Was this an honest mistake or just passing a brain fart? Or is the thought of people with this problem searching all over their radiators for nonexistent temp switches funny?
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To be fair the 3.9 V8 had a coolant temp sensor switch beside the thermostat which activated the condensor fans independantly if coolant temp got over 95 deg. He might have been referring to this :eek: I by-passed my (faulty) switch to have them running continuously when I had to remove the Viscous fan on my RRC.

Thats why I'm surprised that the DSE doesn't seem to do it, you would imagine that it makes a good back up in Hot climates. I must check on Faultmate to see if it's something that can be turned on although looking at the ETM it doesn't seem so.
 
The DSE fans can run at full speed or half speed, they run either in series or parallel under relay control. One fan has a permanant 12 volts the other permanant ground, they are coupled in series by a relay, or in parallel by two more relays. All the relays are under the control of the tri state switch and the pressure switch. It is all detailed clearly in the electrical section of RAVE.
 
Datatek said:
The DSE fans can run at full speed or half speed, they run either in series or parallel under relay control. One fan has a permanant 12 volts the other permanant ground, they are coupled in series by a relay, or in parallel by two more relays. All the relays are under the control of the tri state switch and the pressure switch. It is all detailed clearly in the electrical section of RAVE.
Click to expand...

Yeah but there is no link to the Diesel ECU to switch the fans on in response to coolant temperature as is the case with the Petrol models.
 
SpudH said:
To be fair the 3.9 V8 had a coolant temp sensor switch beside the thermostat which activated the condensor fans independantly if coolant temp got over 95 deg. He might have been referring to this :eek: I by-passed my (faulty) switch to have them running continuously when I had to remove the Viscous fan on my RRC.

Thats why I'm surprised that the DSE doesn't seem to do it, you would imagine that it makes a good back up in Hot climates. I must check on Faultmate to see if it's something that can be turned on although looking at the ETM it doesn't seem so.
Click to expand...
OK, my wording was a little harsh... Sorry Pandy.
I just thought it ridiculous to post something like that especially stated as fact. Speculation needs to be stated as such.
Big Boss hasn't been back yet. He's either head over in the engine compartment or at the local parts supplier looking for temp switches that aren't going to be there :doh:

I can't recall ever seeing a wire from the DDE ECU ro the fan relays so I'd speculate (see :p) that switching a soft option via faultmate is not poss.
 
SpudH said:
Yeah but there is no link to the Diesel ECU to switch the fans on in response to coolant temperature as is the case with the Petrol models.
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I didn't say there was any control from the engine ECU on the diesel. As you say there is none, the only link from the engine ECU to the HEVAC is the aircon grant line which enables the aircon. Look at section K4 page 14 of RAVE for the relays which are 13, 14, 18 & 19 for the diesel. Removing fuse F31 (30amp) in the engine compartment fuse box will stop the fans:D
 
Datatek said:
I didn't say there was any control from the engine ECU on the diesel. As you say there is none, the only link from the engine ECU to the HEVAC is the aircon grant line which enables the aircon. Look at section K4 page 14 of RAVE for the relays which are 13, 14, 18 & 19 for the diesel. Removing fuse F31 (30amp) in the engine compartment fuse box will stop the fans:D
Click to expand...

On my DSE i have a none standard temp sensor fitted in the top hose. Often wondered what it was for, when i stripped intercooler out for cleaning it appears that the aircon fans are coupled to this sensor through a relay. Apparently to assist the cooling, as the guy who had it before me did a lot of towing abroad in hotter climes. So they can be utilised in this way with a bit of jiggery pockery.
 
wammers said:
On my DSE i have a none standard temp sensor fitted in the top hose. Often wondered what it was for, when i stripped intercooler out for cleaning it appears that the aircon fans are coupled to this sensor through a relay. Apparently to assist the cooling, as the guy who had it before me did a lot of towing abroad in hotter climes. So they can be utilised in this way with a bit of jiggery pockery.
Click to expand...

Just bought the temperature sensor to do that, I want to get rid of the engine driven fan:D
 
Datatek said:
Just bought the temperature sensor to do that, I want to get rid of the engine driven fan:D
Click to expand...

The one on mine seems to have an adjuster on it. Have never tried playing with it though, to be honest i have never noticed them coming on except when aircon is running. So it must be set pretty high as i said to aid cooling when the ambient is high and the engine is working hard. Seems a good notion to use them in that way though as the engine may run a little more efficiently without the viscous fan.
 
wammers said:
The one on mine seems to have an adjuster on it. Have never tried playing with it though, to be honest i have never noticed them coming on except when aircon is running. So it must be set pretty high as i said to aid cooling when the ambient is high and the engine is working hard. Seems a good notion to use them in that way though as the engine may run a little more efficiently without the viscous fan.
Click to expand...

Trial and error for the temperature setting unless you have a meter that will give you a reading, on my last 4 X 4, 95C seemed to be about the optimum to switch the fans on. Up to 2mpg to be gained without the viscous fan on past experience and much quicker warm up in winter plus better temperature control when towing in hot weather.:D When I eventually find time to do it I will post the results:D:D

Kenlowe sell the stats but you can get a similar product to do the job at a much lower price from www.cpc.co.uk
 
Datatek said:
Trial and error for the temperature setting unless you have a meter that will give you a reading, on my last 4 X 4, 95C seemed to be about the optimum to switch the fans on. Up to 2mpg to be gained without the viscous fan on past experience and much quicker warm up in winter plus better temperature control when towing in hot weather.:D When I eventually find time to do it I will post the results:D:D

Kenlowe sell the stats but you can get a similar product to do the job at a much lower price from www.cpc.co.uk
Click to expand...

Good let me know how you get on. As mine is already rigged up it would be a simple task to remove the fan and run on the electric ones. If they actually work that is. Will have a play when weather gets a little warmer.
 
Now is the time to play, less risk of overheating and quicker warm up. Just adjust the stat control down when the engine is hot until the fans come on, then back the other way until they just switch off and that should be a good setting. Then bin the viscous fan and see how you go, keep a good eye on the temp guage.

Just got an EAS fault today, so will have to fix that tomorrow! Bloody rain!
 
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