944 engine not hot enough,,,which fan to pull?

Beirut944 · 02-20-2015, 10:12 AM

HI
In Lebanon at the moment its really cold and i noticed that the car is taking 20 minuties to warm up around town. On the freeway it doesn't hear up completely which is worrying me. The needle hardly gets out of the main 'bar' at the bottom.

During this cold spell, would it be wise to disconnect one of the fans? I was thinking of pulling one of the fuses, but which one?

Has anyone done this in Europe or North America during the winter?

Best

MJ

AaronM · 10:28 AM

The issue you describe is not the result of the fans.

Most likely, someone has removed the thermostat from your car (or your thermostat has failed open) and, as a result, coolant is always flowing through the radiator, which is resulting in over-cooling.

Remember, the purpose of a thermostat is NOT to help the engine stay cool. The purpose of a thermostat is to keep the engine warm and to ensure that the coolant temperature never falls below the thermostat's set point (stock for these cars is that the thermostat begins to open at 83 C +/- 2 C and is full open by 90 C).

The stock radiator fans don't turn on until 92 C (a little more than halfway between the two white lines on the gauge for 1985.5 and later cars), and that's just low speed. Stock high speed is 102 C (just a hair above the upper white line), though the A/C can also trigger the high speed fans at lower coolant temps based on A/C line pressures. If you're seeing the temp hover around the first white line, that's 80 C, so the fans shouldn't be coming on at all at that temp (unless someone has replaced the fan switch with a lower temp unit).

You probably need to put a new thermostat in the car.

Beirut944 · 02-20-2015, 09:35 PM

Quote:

Originally Posted by AaronM

The issue you describe is not the result of the fans.

Most likely, someone has removed the thermostat from your car (or your thermostat has failed open) and, as a result, coolant is always flowing through the radiator, which is resulting in over-cooling.

Remember, the purpose of a thermostat is NOT to help the engine stay cool. The purpose of a thermostat is to keep the engine warm and to ensure that the coolant temperature never falls below the thermostat's set point (stock for these cars is that the thermostat begins to open at 83 C +/- 2 C and is full open by 90 C).

The stock radiator fans don't turn on until 92 C (a little more than halfway between the two white lines on the gauge for 1985.5 and later cars), and that's just low speed. Stock high speed is 102 C (just a hair above the upper white line), though the A/C can also trigger the high speed fans at lower coolant temps based on A/C line pressures. If you're seeing the temp hover around the first white line, that's 80 C, so the fans shouldn't be coming on at all at that temp (unless someone has replaced the fan switch with a lower temp unit).

You probably need to put a new thermostat in the car.

thanks a lot Aaron. I'm guessing the previous owner pulled it out altogether - a common practice in the middle east. I will have to work out where it it is...

Beirut944 · 11:22 PM

Quote:

Originally Posted by Beirut944

thanks a lot Aaron. I'm guessing the previous owner pulled it out altogether - a common practice in the middle east. I will have to work out where it it is...

Little confused as you what you said about the fans. Are you saying that both of them are wired to a thermostatic switch (i guess) in the radiator? I htink this is where my problem is. In my case only ONE is. The other one comes on the moment i switch the ignition on.

Is it possible that the previous owner hot wired one directly? I noticed there are two fuses. WHen i saw that there were 2, i just assumed that one was for the 'always on' one, and the other was for the thermo one.

Put me out of my misery please

MJ

AaronM · 02-21-2015, 10:52 AM

Quote:

Originally Posted by Beirut944

The other one comes on the moment i switch the ignition on.

Something is definitely wrong if that's what's happening.

Looking back on your posts, it seems you have a 1986 944, so I will give you the information for the later cars. The fan operation on early cars is somewhat different, but even in their case, no fan should come on with the ignition.

On 1985.5 and newer 944s, there are two radiator fans. BOTH are wired to the thermofan switch. Neither fan should be on until the thermofan switch triggers low-speed operation at 92 C. (NOTE: There are aftermarket "low temp" thermofan switches available in 85 C and 75 C varieties and it is relatively common for prior owners to install these incorrect fan switches, so you cannot be 100% certain of having the stock 92 C switch in your car without looking at it.)

Basically, on the later 944 (and your '86 model is a later 944), both fans should always operate in tandem. Both off, both on low speed, or both on high speed.

With the stock 83 C thermostat, the engine should warm up to 83 C (just above the first white line) within 5-10 minutes of driving, even when ambient air temperatures are near 0 C. Remember, the thermostat blocks off the radiator until it opens. So whether the fans are on or not should have no effect on warm-up time because the coolant is simply staying in the block.

It sounds to me as though a previous owner very inexpertly attempted to deal with what he or she thought was an overheating issue. You need to address the problem with your always-on fan, but you also need to replace the thermostat with the appropriate 83 C stock unit. I still believe there is an issue with your thermostat given the long warm-up times you are reporting.

I would start by replacing your thermostat, and also by replacing the cooling fan relay (relay G10 in the factory wiring diagrams). It is possible, though unlikely, that the always-on fan is the result of a failed relay. Usually a failed relay will make the fan run even if the ignition is off, but I'd still change out the relay just to eliminate it as a possibility (and because old stiff is old).

If the fan continues to run any time the ignition is on even after you have replaced the relay, then you have the unenviable task of going through the wiring and trying to find out where the wiring fault is.

thomasryan · 02-21-2015, 06:40 PM

Great explanation

Foxxywoxxy · 02-21-2015, 11:18 PM

My fans are also always on as soon as I put the key in as well.. My engine heats up to the second line (center line) and barely ever moves, unless I let it just sit in which it hovers around the third bar.

AaronM · 10:02 AM

Quote:

Originally Posted by Foxxywoxxy

My fans are also always on as soon as I put the key in as well.. My engine heats up to the second line (center line) and barely ever moves, unless I let it just sit in which it hovers around the third bar.

There is no "center line" on the temperature gauge for the late cars. You have an early car, which has a different gauge. See here: Water Temp Gauge This is why I specified that the information I gave Beirut was for the 1985.5 and later cars.

That said, your wiring is wrong if the fan comes on whenever the key is in. Given the rats' nest of wiring that you've shown in other threads, it is not at all surprising to hear that your car's radiator fan wiring is also screwed up.

On the early cars there are two setups:

Without A/C there is only one fan. It should turn on low-speed at 92 C, and will eventually turn on high speed if water temps continue to climb.

With A/C, the early cars have two fans. Only one will run at low-speed, though it should not come on until coolant temp in the radiator reaches 92 C. For high speed, however, both fans will come on.

In early cars, if the A/C is on, both fans will run all the time. So if you have the A/C on, the fans should be running regardless of coolant temp.

The later cars use a pressure switch in A/C lines and don't force the fans on unless A/C high-side pressures exceed about 200 PSI.

Foxxywoxxy · 02-22-2015, 09:14 PM

Oh I just lovean the wiring to in my car, but to be honest my wiring had little to no problems until a headlight motor shorted and melted my headlight wiring, still working on getting that fixed. The only thing I don't understand is that if something is wrong with my wiring for my thermostat and fans whydo temps read normal levels? Is it really something that I > need < to get fixed asap if the system is still running fine? Where on my list should this repair be because I'm a little lost on what order the work I need to get done needs to get done

What I have so far

1: headlight wiring harness
2: headlight motor replacement
3: passenger mirror replacement
4: stuck seats
5: engine rebuild (state of mind thing)

Where should I be putting this repair in that list? I'm sorry I ask a lot of questions here but I've only had the car since October, and it's my first car and I'm trying to get it as close to restored as I can.
How much work am I looking at to fix the fans?

AaronM · 09:30 AM

OK, first of all, hijacking someone else's thread usually is considered bad form because it creates clutter. People have to wade through each post to find out whether it's responding to the original poster ("OP") or to the questions brought up later by the hijacker. That said, you're new and may not have understood that, so I'll go ahead and answer here.

Quote:

Originally Posted by Foxxywoxxy

if something is wrong with my wiring for my thermostat and fans why do temps read normal levels?

A close reading of my explanations for Beirut should have already explained this, but I'll go through it again in more detail for you.

First of all, the thermostat has no wiring. It's not electric. Based on the temps you're seeing, your thermostat appears to be working fine.

The issue you have is with the fan, the fan's wiring, or the thermofan switch. The thermofan switch is NOT the thermostat. The thermostat is located in the water pump and is used to stop coolant from going through the radiator until the engine is warm. The thermofan switch is in the radiator and is a trigger for the fans.

The reason temps can be fine even with your fan always running is because the thermostat is working. When the coolant temp is below 83 C, the thermostat is closed and coolant simply recirculates through the engine block without ever going through the radiator. It is only after the thermostat opens that coolant from the engine is able to go through the radiator.

So, when the thermostat is closed, it doesn't matter whether the fan is running or not because there's no coolant flow through the radiator.

As long as the thermostat is functioning properly, an always-on radiator fan won't actually hurt anything. When ambient temperature is below about 5 C and you're sitting still, the car will probably run closer to the 83 C thermostat point than normal, but not enough so to cause problems. In warm weather, there really won't be any practical difference. Except that you're wearing out the fan (it's not designed to be running all the time) and you're wasting gas (fans take power to run, which places more load on the alternator and causes the engine to burn more fuel).

If the problem is the result of a short circuit in the wiring, you're also sort of playing Russian roulette because you don't know where the short is or whether it's getting worse and might affect something else on the car.

Quote:

Originally Posted by Foxxywoxxy

Is it really something that I > need < to get fixed asap if the system is still running fine?

For me, personally, sorting out wiring faults is high on my list. At the very least I'd want to find out whether the issue was the result of a fault (e.g. a short-circuit, etc.) or was the result of something intentional by a former owner (I've heard of people simply intentionally wiring the fan permanently on to avoid having to replace a failed thermofan switch).

If I've assessed it and there's no risk of the wiring getting worse, I'd say that it's not an immediately critical repair.

Quote:

Originally Posted by Foxxywoxxy

Where on my list should this repair be because I'm a little lost on what order the work I need to get done needs to get done

What I have so far

1: headlight wiring harness
2: headlight motor replacement
3: passenger mirror replacement
4: stuck seats
5: engine rebuild (state of mind thing)

Headlights are obviously a high priority. As is the mirror.

If the seats are stuck in a way that makes it impossible for the driver to be in a comfortable and safe driving position, they're also a priority.

As for engine rebuilds, these engines are sturdy. If you have 150,000 miles or more I could see doing the rod bearings out of precaution, but the rest of the engine is unlikely to have problems. So unless you have a direct indication that something is failing, I wouldn't bother with a full engine rebuild.

I would put sorting out the fan wiring either above or below the seat issue, depending on whether the seat issue prevents the use of a safe driving position.

Quote:

Originally Posted by Foxxywoxxy

How much work am I looking at to fix the fans?

That depends entirely on what, exactly, is wrong. What I can tell you though is that I don't buy used cars with wiring problems because it's a royal pain in the butt to go through a harness and look for short circuits.