classic relays - cooling fans specifically...
Discussion
I really do not understand electrics , and relays have always confused me more than the square root of a negative number - so please be gentle and considerate with your replies...
The cooling fans on my Maserati Indy are random to say the least, partly because they are almost 50 years old and Italian, and I'm sure a lot due to them being 'modified' by the PO, but this morning I thought I'd try to get to the bottom of the problem. 3 hours later I'm even more confused.
The system is as far as I can understand it in four stages, (1) - thermostatic control in rad, (2) - first relay (controls first fan), (3) - second relay (controls second fan), (4) - fans.
Starting from (4), both fans when connected to 12v run, so that isn't the problem. The thermo-switch on the rad I have tried wiring together directly and disconnecting completely, so (1) seems to make no difference.
The fans are both on an over-ride switch, which when ignition is on you can hear the relay switching but no fan movement - testing with a voltmeter though there does seem to be power switching over to the appropriate terminals when the over-ride switch is activated. The relays are original looking units (Bosch) with 5 terminal (4 being used) - central one which appears to be thick and constantly live, 2 side ones which have thin wires, one seems to be earth and the other carries around 11v when the over-ride switch is flipped, the final wire on the opposite side is thicker and I presume goes to the fan itself. (all the wires disappear into conduit/trunking so tracing them exactly is difficult as their colour even seems to change along the route).
In my simple electro-brain I imagine the thin wires when switched (by the over-ride switch) allows the thicker central live and thicker fan feed wires to be connected inside the relay allowing current to flow to the fan. However, that doesn't happen at the mo - it used to, but if the over-ride switch is on and I put a wire between thin switch +ve and fan thick feed wire then it runs - that kinda makes sense to me. What makes no sense is that if I connect the central thick +ve to the thick fan feed then the fan doesn't move.
This is even confusing me to type.
All I can think is that the thin switch +ve has a slightly higher voltage (around 11) when measured against the thick permanent middle live (around 9-10v). Could it be that the central live that should be just being switched on doesn't have the oomph to run the fan? whereas the switch itself carries just enough current to make the fan run?
I'm not even getting into what the second relay does.
Please help....currently I can only drive the car in the current weather conditions and in no traffic....
Cheers
Joe
The cooling fans on my Maserati Indy are random to say the least, partly because they are almost 50 years old and Italian, and I'm sure a lot due to them being 'modified' by the PO, but this morning I thought I'd try to get to the bottom of the problem. 3 hours later I'm even more confused.
The system is as far as I can understand it in four stages, (1) - thermostatic control in rad, (2) - first relay (controls first fan), (3) - second relay (controls second fan), (4) - fans.
Starting from (4), both fans when connected to 12v run, so that isn't the problem. The thermo-switch on the rad I have tried wiring together directly and disconnecting completely, so (1) seems to make no difference.
The fans are both on an over-ride switch, which when ignition is on you can hear the relay switching but no fan movement - testing with a voltmeter though there does seem to be power switching over to the appropriate terminals when the over-ride switch is activated. The relays are original looking units (Bosch) with 5 terminal (4 being used) - central one which appears to be thick and constantly live, 2 side ones which have thin wires, one seems to be earth and the other carries around 11v when the over-ride switch is flipped, the final wire on the opposite side is thicker and I presume goes to the fan itself. (all the wires disappear into conduit/trunking so tracing them exactly is difficult as their colour even seems to change along the route).
In my simple electro-brain I imagine the thin wires when switched (by the over-ride switch) allows the thicker central live and thicker fan feed wires to be connected inside the relay allowing current to flow to the fan. However, that doesn't happen at the mo - it used to, but if the over-ride switch is on and I put a wire between thin switch +ve and fan thick feed wire then it runs - that kinda makes sense to me. What makes no sense is that if I connect the central thick +ve to the thick fan feed then the fan doesn't move.
This is even confusing me to type.
All I can think is that the thin switch +ve has a slightly higher voltage (around 11) when measured against the thick permanent middle live (around 9-10v). Could it be that the central live that should be just being switched on doesn't have the oomph to run the fan? whereas the switch itself carries just enough current to make the fan run?
I'm not even getting into what the second relay does.
Please help....currently I can only drive the car in the current weather conditions and in no traffic....
Cheers
Joe
A relay is just a switch that is remotely operated by (often smaller amount of) electricity. A 5 terminal one is really a 3 terminal switch and the 2 terminal 'remote control'.
If you look carefully on the side or top of the relay it should show you which pins the switch connects to and which pins the 'remote control' connects to like this:
Like in the picture - if you put 12V into pins 85 - 86 the switch will connect 30 to 87.
Ignore the value of the funny pin numbers, just match them to the base which should have them stamped on.
When you buy a replacement try to get one that matches your old one - should be quite possible, it may also be worth checking it can handle the current which would be equal or greater than the rating of the fuse used for the fan.
This sort of thing:
https://www.ebay.co.uk/itm/5-pin-12v-40Amp-automot...
They are reasonably standardised so you should be able to ID yours.
If you look carefully on the side or top of the relay it should show you which pins the switch connects to and which pins the 'remote control' connects to like this:
Like in the picture - if you put 12V into pins 85 - 86 the switch will connect 30 to 87.
Ignore the value of the funny pin numbers, just match them to the base which should have them stamped on.
When you buy a replacement try to get one that matches your old one - should be quite possible, it may also be worth checking it can handle the current which would be equal or greater than the rating of the fuse used for the fan.
This sort of thing:
https://www.ebay.co.uk/itm/5-pin-12v-40Amp-automot...
They are reasonably standardised so you should be able to ID yours.
I would test every section of wiring separately until you find the bit that doesn't work.
Tools
- a length of wire
Remember to always have fingers, loose clothes, clear of fan in case it does work.
Ignition off
Wire from battery to fan (tests fan and earth)
Ignition and override on
Wire from fan to earth (tests earth)
Relay output to fan (tests wire from relay to fan)
Battery to relay power in (tests 12v feed)
Battery to relay signal in
Relay signal out to earth
Relay power in to power out
etc, try all combinations
A bulb wired to crocodile clips is also useful, easier to see than a voltmeter - eg connect it to the fan output of the relay while you're in the car turning overide and ignition on and off
It's odd that you're getting different voltages on some wires - cars either have 12v or 0v (occasionally 6v) so anything less means a dodgy connection or wire.
Edit - re reading the OP it sounds like the relay main contacts have burned out.
Tools
- a length of wire
Remember to always have fingers, loose clothes, clear of fan in case it does work.
Ignition off
Wire from battery to fan (tests fan and earth)
Ignition and override on
Wire from fan to earth (tests earth)
Relay output to fan (tests wire from relay to fan)
Battery to relay power in (tests 12v feed)
Battery to relay signal in
Relay signal out to earth
Relay power in to power out
etc, try all combinations
A bulb wired to crocodile clips is also useful, easier to see than a voltmeter - eg connect it to the fan output of the relay while you're in the car turning overide and ignition on and off
It's odd that you're getting different voltages on some wires - cars either have 12v or 0v (occasionally 6v) so anything less means a dodgy connection or wire.
Edit - re reading the OP it sounds like the relay main contacts have burned out.
Edited by john2443 on Monday 5th March 07:32
yosini said:
The fans are both on an over-ride switch, which when ignition is on you can hear the relay switching but no fan movement - testing with a voltmeter though there does seem to be power switching over to the appropriate terminals when the over-ride switch is activated. The relays are original looking units (Bosch) with 5 terminal (4 being used) - central one which appears to be thick and constantly live, 2 side ones which have thin wires, one seems to be earth and the other carries around 11v when the over-ride switch is flipped, the final wire on the opposite side is thicker and I presume goes to the fan itself. (all the wires disappear into conduit/trunking so tracing them exactly is difficult as their colour even seems to change along the route).
Where does the wiring from the thermoswitch come into all this ? Are you sure that only four of the five terminals on the relays are used ? It could be designed so that either/both the thermoswitch and the override switch operate the relay - in which case, five terminals would be needed. To check the relay itself, all you need is a length of wire with male spades on both ends which you use to bridge the thick 12v feed from the battery (central socket) to the socket thick wire to the fan. If the fan operates then given your other readings for the override switch circuit, it indicates that the relay is kaput.Are there any markings on the relays ?
Hi,
I'm trying to make sense of the previous owners's wiring - I know he wired in the over-ride switch as there are notes he made to that effect. I haven't removed any wires and - on closer inspection Relay 1 has 5 terminals but 2 of them are paired (red lead bottom left in image) on this one you can't make out any markings on the relay. The second relay - more visible in the picture definitely has one spare (87), presumably this is switchable from that to 87b where the fan red wire is connected. The puzzling thing is that if I bypass either relay by connecting directly as you mention between red and yellow then there is no action from either fan. But if I connect directly from the skinny switch live (in this case the light blue) to the red then the fan runs.
I'm trying to make sense of the previous owners's wiring - I know he wired in the over-ride switch as there are notes he made to that effect. I haven't removed any wires and - on closer inspection Relay 1 has 5 terminals but 2 of them are paired (red lead bottom left in image) on this one you can't make out any markings on the relay. The second relay - more visible in the picture definitely has one spare (87), presumably this is switchable from that to 87b where the fan red wire is connected. The puzzling thing is that if I bypass either relay by connecting directly as you mention between red and yellow then there is no action from either fan. But if I connect directly from the skinny switch live (in this case the light blue) to the red then the fan runs.
One of the things that can confuse the situation when electrical fault finding is that a wire or terminal can have 12V present at it, but can also have such a high resistance between the battery terminal and the point where you're measuring the voltage that it's incapable of delivering the current required to operate the light/fan/motor/whatever is connected to it.
To compound this, a circuit can have more than one defective item in it.
While I am no electrical guru, a circuit that is relatively simple such as this should be susceptible to some basic fault-testing.
Working backwards "up" the circuit from the fan back to the battery, can you first check that there is a low-resistance connection between the fan's +ve input and the fat (yellow?) feed wire that's attached to the relay? If there is, will the fan spin if 12V taken from the battery is connected directly to the red fan power supply cable? Based on your earlier comments the answer should be yes.
If yes, put the known good 12V supply onto the fan power input cable connection on the relay and switch the override switch on. If it operates now, the existing power input must be faulty (high resistance is likely).
If not, there is a fault in the relay, or it's not connected correctly. There may of course be other faults which have yet to be found.
I believe the above should give an idea of where to look however.
To compound this, a circuit can have more than one defective item in it.
While I am no electrical guru, a circuit that is relatively simple such as this should be susceptible to some basic fault-testing.
Working backwards "up" the circuit from the fan back to the battery, can you first check that there is a low-resistance connection between the fan's +ve input and the fat (yellow?) feed wire that's attached to the relay? If there is, will the fan spin if 12V taken from the battery is connected directly to the red fan power supply cable? Based on your earlier comments the answer should be yes.
If yes, put the known good 12V supply onto the fan power input cable connection on the relay and switch the override switch on. If it operates now, the existing power input must be faulty (high resistance is likely).
If not, there is a fault in the relay, or it's not connected correctly. There may of course be other faults which have yet to be found.
I believe the above should give an idea of where to look however.
Edited by 9xxNick on Monday 5th March 22:16
yosini said:
The puzzling thing is that if I bypass either relay by connecting directly as you mention between red and yellow then there is no action from either fan. But if I connect directly from the skinny switch live (in this case the light blue) to the red then the fan runs.
To me that suggests an issue in the yellow supply. The override switch is correctly triggering the relay (because you can hear it, and because even if the trigger current is low, that's OK because that's why you have a relay, so you only need low current through the switch contacts), but because there's nothing (or not enough) coming in on the high-current supply wire (yellow), then the fan still doesn't run. You mentioned 9-10v on the yellow wire, so that suggests some connection issue further up the line which, if it's dropping voltage, may also be affecting current. I'm not sure about the fans, whether they would turn slowly or just not turn at all if the supply isn't sufficient, though it sounds like the latter. The fact that wires change colour through the loom is concerning, but only because that's another (hidden) connection which could be causing, or exacerbating, the issue.I think the fifth terminal on your relays is just a duplicate output terminal, so when the relay is activated, the yellow supply wire would be connected to both of the output terminals. Think of headlamps - you either need to put the two cables (one to each lamp) into a single spade connector on a four-contact relay, or you can have separate wires and separate connectors like yours seem to have. The diagram on the top of the relay that globs showed a photo of seems to be different, IMO, in that activation switches current from being connected to 87a, to being connected to 87. So that one looks more like a change-over relay.
Edited by droopsnoot on Tuesday 6th March 11:18
yosini said:
You can see the two wires on the left will be the 'activate' or 'remote control' input.
the yellow is clearly the bottom of the fork that flicks between the Red and the spare (unused).
So a good check would be to flick on the override and then measure with a meter the voltage on the yellow and red. If the yellow is low start looking at fuses. If the yellow is high and the red is low it's a relay fault.
solved - well at least to some extent. Very good idea whoever suggested running a live directly from the +ve battery terminal to the yellow centre feed. When I did that everything worked fine again - the thermo switch when bridged clicked in fan 1, the override switch also clicks in this fan separately and then the override switch to fan 2 also worked. Brilliant.
So presumably it is just not getting enough current through the yellow centre +ve feed, so I need to trace that back and find where the weak link is....
I feel I understand a lot more about relays, and electrics in general now, so thanks everyone. Much safer experimenting on car electrics than on home ones....
Stay safe folks and thanks again
Joe
So presumably it is just not getting enough current through the yellow centre +ve feed, so I need to trace that back and find where the weak link is....
I feel I understand a lot more about relays, and electrics in general now, so thanks everyone. Much safer experimenting on car electrics than on home ones....
Stay safe folks and thanks again
Joe
Great news!
If you can see where the wires enter the fusebox you should look for a fat yellow one which will be the other end of the yellow feed to the relay.
Wires in general look after themselves so I suspect you have a loose or corroded connection into the fusebox or the actual fuse or fuse connections. You may find the fan starts just by touching or moving the right fuse.
The move to blade style fuses in the 1980s solved many electrical problems in cars. Once you have cleaned up and fixed the fault consider buying some ACF50 and spraying any exposed copper as it will protect from the elements.
12V electrics are great for electrocution safety but avoid fitting battery terminals with any rings on your fingers: there's still a potential 700+ amps sitting around waiting for a quick path home via a white hot wedding ring...
If you can see where the wires enter the fusebox you should look for a fat yellow one which will be the other end of the yellow feed to the relay.
Wires in general look after themselves so I suspect you have a loose or corroded connection into the fusebox or the actual fuse or fuse connections. You may find the fan starts just by touching or moving the right fuse.
The move to blade style fuses in the 1980s solved many electrical problems in cars. Once you have cleaned up and fixed the fault consider buying some ACF50 and spraying any exposed copper as it will protect from the elements.
12V electrics are great for electrocution safety but avoid fitting battery terminals with any rings on your fingers: there's still a potential 700+ amps sitting around waiting for a quick path home via a white hot wedding ring...
Globs said:
Great news!
12V electrics are great for electrocution safety but avoid fitting battery terminals with any rings on your fingers: there's still a potential 700+ amps sitting around waiting for a quick path home via a white hot wedding ring...
And avoid fiddling around with the high tension ignition stuff on a damp morning – worst jolt I've ever had 12V electrics are great for electrocution safety but avoid fitting battery terminals with any rings on your fingers: there's still a potential 700+ amps sitting around waiting for a quick path home via a white hot wedding ring...
Globs said:
12V electrics are great for electrocution safety but avoid fitting battery terminals with any rings on your fingers: there's still a potential 700+ amps sitting around waiting for a quick path home via a white hot wedding ring...
Yes, I have a lasting reminder that (a) when you add a spotlamp relay, you should insulate the spade connectors, (b) you should also put a fuse on it, not just wire it directly to the battery and intend to "do that bit later", and finally (c) when removing said spotlamp relay because you've sold the car at a low price without any of the extras, you should either disconnect the battery, or not wear a watch with a metal strap while reaching blindly up under the dash. I got a nice big scar that I still have 30+ years later, but fortunately the damage to my other hand that I incurred while trying to hastily remove the watch have disappeared completely.Glad the problem appears to be solved.
Sorry for the thread resurrection.
My 1977 Merak fans go on as soon as you switch the ignition on. I've done some few tests and they are inconclusive.
Next step is now to replace the relays. Can I replace the ones there (same as in this threads pictures) with a modern relay? If so, any recommendations as to what is best?
Thanks
My 1977 Merak fans go on as soon as you switch the ignition on. I've done some few tests and they are inconclusive.
Next step is now to replace the relays. Can I replace the ones there (same as in this threads pictures) with a modern relay? If so, any recommendations as to what is best?
Thanks
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