Seahag1978 Posted October 22, 2004 Share Posted October 22, 2004 The Brat is almost back together... new tranny, axles, brakes, bearings, etc. (ball joints to come) ...now I need help to tackle the next problem and get parts needed: Symptom: Electric fan doesn't come. Someone installed a manual switch on the dash... one problem, the temperature gauge on dash doesn't move to tell me when to turn it on. I have read in the archives that the cabin heat suffers if the fan runs full time? I know the major parts of this system: radiator, water temperature sender, thermostat, temperature gauge etc... what I need is a simple explanation... what is the order of the chain of events that happen to make all these gizmoes work together?! Yikes! Thanks! Mary Quote Link to comment Share on other sites More sharing options...
thealleyboy Posted October 22, 2004 Share Posted October 22, 2004 The Brat is almost back together... new tranny, axles, brakes, bearings, etc. (ball joints to come)...now I need help to tackle the next problem and get parts needed: Symptom: Electric fan doesn't come. Someone installed a manual switch on the dash... one problem, the temperature gauge on dash doesn't move to tell me when to turn it on. I have read in the archives that the cabin heat suffers if the fan runs full time? I know the major parts of this system: radiator, water temperature sender, thermostat, temperature gauge etc... what I need is a simple explanation... what is the order of the chain of events that happen to make all these gizmoes work together?! Yikes! Thanks! Mary The non-operable temp guage is a drag. Without knowing the engine temp, you can't even determine if the fan should even be coming on at all!! If I were you, I'd install a basic aftermarket temp sensor/guage. That way, you'll at least have somewhere to start. You are grasping at straws otherwise... good luck, John Quote Link to comment Share on other sites More sharing options...
Seahag1978 Posted October 23, 2004 Author Share Posted October 23, 2004 The non-operable temp guage is a drag. Without knowing the engine temp, you can't even determine if the fan should even be coming on at all!! If I were you, I'd install a basic aftermarket temp sensor/guage. That way, you'll at least have somewhere to start. You are grasping at straws otherwise... good luck, John Hi John, This car will (by spring) be a show car... I need to get it back to the original configuration. The paint or decal work isn't in original colors but they don't really count that for some reason... nor do they count steering wheels, shifter knobs, foot pedals... I don't know all the rules (yet)?? Instrumentation and interior counts though? Unless it's reconfigured to be custom... then the rules change again? Now, do any of the other parts cause the temperature guage on the dash to malfunction? I guess that's where I need to start. I am soooo confused... Quote Link to comment Share on other sites More sharing options...
hops Posted October 23, 2004 Share Posted October 23, 2004 Mary, Sounds like you need to get a new radiator fan switch. It mounts right next to the fan in the radiator. It is a common item to go out in '78 Brats Klaus The Brat is almost back together... new tranny, axles, brakes, bearings, etc. (ball joints to come)...now I need help to tackle the next problem and get parts needed: Symptom: Electric fan doesn't come. Someone installed a manual switch on the dash... one problem, the temperature gauge on dash doesn't move to tell me when to turn it on. I have read in the archives that the cabin heat suffers if the fan runs full time? I know the major parts of this system: radiator, water temperature sender, thermostat, temperature gauge etc... what I need is a simple explanation... what is the order of the chain of events that happen to make all these gizmoes work together?! Yikes! Thanks! Mary Quote Link to comment Share on other sites More sharing options...
thealleyboy Posted October 23, 2004 Share Posted October 23, 2004 Yes, the thermoswitch circuit is likely to be the reason the fan isn't coming on. Still, I would want to get that guage working again. I'll see if I can dig up some materials on the Brats from that era. Cool that you want to keep things original. I'm into vintage Mustangs, and understand how much of a challenge it can be to do a faithful resto on those older cars. good luck, John Quote Link to comment Share on other sites More sharing options...
Seahag1978 Posted October 24, 2004 Author Share Posted October 24, 2004 bump. Please. Talk to me like I'm 5 years old... the water pump sends the water into the motor comes back out hot... then? What does the thermostat, water temperature sender, temperature gauge (especially this), thermo fan switch, and any other pieces parts do? And in what order? The books tells me all the fine details... the saying goes... you can't see the forest for the trees. I need the big picture. Thanks! Mary Quote Link to comment Share on other sites More sharing options...
NorthWet Posted October 24, 2004 Share Posted October 24, 2004 bump. Please. Talk to me like I'm 5 years old... the water pump sends the water into the motor comes back out hot... then? What does the thermostat, water temperature sender, temperature gauge (especially this), thermo fan switch, and any other pieces parts do? And in what order? The books tells me all the fine details... the saying goes... you can't see the forest for the trees. I need the big picture. Thanks! Mary OK... Heated water comes to thermostat housing... on the side of the T-stat housing is a temperature sendor unit for the temp gauge. The temp sender works by grounding the power coming to it from the temp guage: As water temp increases the sender' resistance decreases. So for this to work, the temp gauge has to be getting (proper) power, the internals have to be working, the wiring to the sender has to be unbroken and ungrounded, and the sender has to be working. The hot water passes through the t-stat, through the "upper" radiator house to radiator side-tank. On this side-tank, near the drain plug, is a thermoswitch used to control the electric fan. (The water then passes from this tank across the radiator tube&fins, into other tank, through lower radiator hose and back to water pump... sorry but you said... ) Anyway, once the water's temp reaches the setpoint for the thermoswitch, it switches "on" and allows the fan to come on. (Can't remember if it switches ground or power on subie fans... too tired to look.) Quote Link to comment Share on other sites More sharing options...
Seahag1978 Posted October 24, 2004 Author Share Posted October 24, 2004 Thank you... thank you! Knowing the course this system takes will help track down the problem... it's second nature for you guys... and they don't get into the fundamentals in the manuals... the concentration is all on individual parts. I wish I had a dummy guide showing the fundamentals... gas goes in... spark goes in... boom... pushes this and moves that... spins this... anyone know of one? Thanks again! Mary Quote Link to comment Share on other sites More sharing options...
thealleyboy Posted October 24, 2004 Share Posted October 24, 2004 and they don't get into the fundamentals in the manuals... the concentration is all on individual parts. I wish I had a dummy guide showing the fundamentals... gas goes in... spark goes in... boom... pushes this and moves that... spins this... anyone know of one? Let me suggest the long-out-of-print "Readers Digest Complete Automotive Repair Manual". This was the dummy guide for cars, before there were dummy guides. But this was not a fluff book by any means. In fact, lots of excellent mechanics, both professional and amature, got their start with this book. It covers the fundamentals as well as any book I've ever seen, and was actually fairly comprehensive for the cars of that era (late 70's). Even though it's a bit dated today, the fundamentals still apply. If you are into older cars, this is the best general repair manual you could ever hope for. Well worth the effort to track down a copy on internet, yard sales, etc. This and "How to Keep your Subaru Alive are two books I highly recommend. John Quote Link to comment Share on other sites More sharing options...
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