Hello. Am facing a problem with the fans of my 4.7 Indy. They switch on too late (>100*) and only stay on for a few seconds before they switch off again. Flushed the cooling system already and exchanged the thermo switches at the radiator but still no luck. The engine heats up to 110 degrees when i am not driving and so far the only solution is to switch the fans on manually with the AC. There seems to be a unit on my AC that is not connected and also at the relays Hope somebody can help. Thanks Dirk Image Unavailable, Please Login
And a pic of the relays. Which is the manufacturer and what serial number? Maybe they need to be replaced? Image Unavailable, Please Login
That wiring looks frightful! The pressure switch on the AC compressor is not in control of your fans for engine cooling purposes so don't worry about that. Typically the fans are put on when you engage the AC for operation whether they are are needed for engine cooling or not. That switch should not be bypassed but fixed. I think on this car it will keep your compressor from running when the charge is too low. Some systems have a high & low switch. Thermostatic switches in the cooling system for fan operation come in a variety of specifications with an on temperature and an off temperature. Perhaps the ones you've installed are the wrong specification. Also, having a manual override for the fans is a typical modification for these older GT cars for use in hot summer weather when one comes in off a high speed road and enters into local traffic. The idea is that you don't want to wait for the fan's thermoswitch to decide to come on as the system is marginal enough that you need all the advantage you can get. But that's a different issue. I can't see how the relays could be affecting this from a temperature standpoint as you described. But I'd check all portions of the circuit including operational voltage drops anyway. Getting the exact and original relays might be a lot more difficult (euro spares or MIE) but obtaining good functioning ones should be relatively simple. The switch below the relays in what appears to be a brake line is probably for the brake lights. Are those relays for the fans or for the headlamps?
Thanks for the reply. Think the relays are for the fans but i might be wrong. The same problem occured before i changed the thermo switches which i got from MIE so think they should be the right ones. The fans switch on, but very late and only for about 3 seconds. Also changed the voltage regulator which was not working properly but now is. Yes, the wiring needs to be done properly and it is on my to do list. The AC is not filled or running so that is why i think the previous owner bypassed the switch. Got the gasket set from MIE and will try to fix it one day but at the mo this is a lower priority.
They are Bosch relays and in my experience they seldom go bad. When they do it is relatively easy to open the cover, clean the contacts and put it back together. Each relay controls one fan. Does your car have one or two thermo switches on the radiator? When they have two thermo switches, each switch will trigger one relay. The thermo switch is usually stamped on the side with the kick in and kick out temperatures. For example if you see 80 - 90 degrees C it means that the switch will close when it reaches 90 degrees C and will open when the water cools down to 80 degrees C. In other words the fan will start at 90 degrees and will continue running until the water temperature drops to 80 degrees. Before you continue replacing parts the first thing to determine is where exactly is the problem. Here are a few test to try: 1. Jump together the two wires going to the radiator thermo switch. One of both fans should run when the ignition switch is on. If only one fan is running make sure there is not another thermo switch on the radiator. If the fan only runs for a few seconds and quits the problem is most likely in the relay or fuse. 2. With the fans running make sure both fans are pulling air in. More than once I've seen fans connected backwards. 3. Buy an infra red thermometer as this is a great tool when working on cooling systems. The temperature of the top radiator hose should closely match the gauge. Ivan
Thanks a lot for your help Ivan. very useful. I have 2 brand new thermo switches installed. Both from MIE. Will check what they say. When i bridge the cable, both fans turn on and blow a great load of air towards the engine. The engine cools down nicely, also when i switch them on through the AC regulator inside. Will definitely check the relay and fuse again. The infrared thermometer is a good recommendation, thanks. Maybe it is just a faulty temp sender unit. The oil temp is fine. Should they both be the same? Thanks again for your help Best Dirk
What happens when you short the wires to one of the thermo units ... does both fans come on or only one? Same question as to what happens when you short the second thermo switch (leaving the first one open)? I am trying to figure out how your fan relays were wired. If the fans are turning on and staying on when the wires to the thermo switch are shorted then you can eliminate the relays and fuse as the problem. This is starting to look like faulty thermo switches which you say are new .. but they could have been made in China. A properly working thermo switch should never close and open within a few seconds. These switches are rather common and were used on Fiats, Alfas, etc. You should be able to find a suitable replacement at a local parts store. Take your old one so that they can match the thread. Key thing is to pay attention to the temperature rating as this determines when the fans start and stop. Get one rated for around 85/75 C. Ivan
Thanks Ivan. The problem was the same with the old ones in, so it would mean that 4 thermo switches are all bad? Maybe it is the sender unit that doesnt match the gauge or has a defect. Only shorted the wires on the thermo switch and the fans came on. Only checked one though. Will try the other tomorrow. Will also try the temp sending unit from the Mexico and check the temp with a thermometer. Hope i will get to the bottom of it. Your help is very much appreciated
Sounds like the temp transducers are at fault as the system works when these are over-ridden and are cutting in too late/ off too early. But as you have tried 4 units I'm not sure what else you could try. I guess you could remove the temp transducers (temp sensors) from the radiators and artificially heat them with a heat gun to see how they operate (with the ignition on), if the fans come on, then off with the heat still being applied then it might indicate where the problem could be?? I'm interested in this thread as it is one of those fault finding jobs that is probably a simple fix, but extensive efforts are needed to find it. Cheers, Rich
I've done this before with thermal switches such as we're discussing here and thermostats too. Use vegetable oil instead of water. It's worth checking. If they are functioning OK and you're still having issues then you must have some very weird water flow issues in that radiator.
Guys, have been thinking about this, staatsof got me thinking about water flow issues... Could there be a airlock in the system??? Have you checked that the complete cooling system has no air in? Regards, Rich
Hey, thanks again for your suggestions. Been flushing the system 3 times with a chemical cleaner and lots of water and what came out was quite clean and not dirty or rusty. This could be good or bad. The radiator looks quite new and it also heats up quite well so i assume there is a sufficiant amout of water/coolant running through it. Will definitely check the temp sensors again and also the relays. Just ordered a laser thermometer that will hopefully give some more insights. Stuart Avery from MIE sent this reply: "When you read your water temp. instrument on the dash, it is receiving a temperature signal from the thermo probe mounted on the thermostat housing. When the fans are activated, it is a signal coming from the thermo switch attached to the radiator. You assume the radiator is the same temperature as the coolant in the thermostat housing, but that is probably not true. If your cooling system is not circulating the coolant in a steady pace, it will become super heated in the engine, but the radiator will only show a mild increase in temperature from convection. A poor circulation often is because of large air cavities in the cooling system, which prevent coolant from moving. If you independently check the actual temperature at the radiator fan switch when the gauge is reading 110, you will likely find the radiator is not 110 near the switch. The switch should cycle on at or near 91c, and then off again at or near 87c. The fan relays are not likely the problem. The old type "canned" relays are Bosch original, but the modern Bosch replacements are the smaller cube type. If you Google the bosch number on the bottom side of the relay, you will likely find the modern cross-reference for a local purchase replacement. Maserati's historically run hot, and in the past owners have found interesting ways to solve problems. One method (even if only temporary) is the put a on/off switch to control the fans rather than the thermo switch on the radiator. If you connect the two wires together at the fan switch, the fans will go on regardless of temperature. If a switch is then added to the wire it could be controlled manually whenever needed. I would first check to see if there is a large disparity in temperatures between the coolant temp. probe mounted at the thermostat housing, compared to the one at the radiator when the gauge reads hot." will try to exclude all possibilities and hopefully will get to the bottom of it. The problem was there before i flushed the system but maybe some air came into the system again even though i tried to get it out at the best of my knowledge.
