Need Help with a '97 Trans Am

Is there a thermocouple attached at the radiator that would turn them on?

Sharing the fuse with the headlights seems odd. I wonder if the manual is correct. Do you have a wiring diagram? It seems very unlikely that all three relays would fail at the same time, but I wonder if they failed at separate times, but it only became obvious when the last one failed.

The most obvious culprit, however, would have to be the thermoswitch that sends its signal to the relays.

The problem started a few weeks ago, at that time I noticed a leak in the water pump, I changed the water pump and temp. sensing unit broke off, So I replaced it at that time. That's new. I wonder if there is something else that might have broke when I had the water pump off??

Are you absolutely sure the engine block is full of water? After replacing water pump the block is empty. If your thermastat was closed when you re-filled radiator, the block may still be empty. Run car with radiator cap off. Car should be facing uphill, to help water flow into top of block. Once thermastat opens keep adding water to radiator until system is completely full. This may be the problem if your car is overheating extremely fast; say within first 5 miles of runnning.

Excellent point!

Question.... I pulled the relay's and there's a wiring diagram on the side. I checked the resistance of the poles against the diagram and didn't find anything wrong. That in and of itself doesn't mean anything I know, but my question is, if I follow the diagram can I jumper across terminals and check to see if my cooling fans come on? And again if they do come on, what does that prove? Anything?

Funny, as I was thinking about your problem this morning, I thought I should have suggested looking for the wiring diagram on the relays, and testing them. (No, I haven't been obsessing over your Trans Am all this time, but you know how things just pop into your head?) Usually, but not always, the thermoswitch supplies the ground to the relay when the thermoswitch closes. If that is the case with your car, then you could put the relay in and ground the wire from the thermoswitch, and the fans should come on (if there is only one wire at the the thermoswitch it has to be a ground.) The relays can be tested off the car by feeding the coil from a 12 volt source, and measuring resistance (or using a powered continuity light, etc) across the output contacts. Ordinarily, you hear a click and the resistance changes from infinity to near zero.

The fans themselves can be tested by powering them from a 12 volt source. (They can draw quite a bit so be prepared for a couple sparks.) The relays can be tested the same way, as above. The thermoswitch can be tested in a pan of water with a multimeter (although there may be some now that are set slightly over 212 -- but I doubt it.) or you could infer that it is not working if all else is. So that covers the possibilities, other than the wires themselves, which you can check with an ohmmeter. (Also, you can verify voltage at the supply side of the relay (meaning the fuse is OK))

... OR ...

The other possibility, if everything seems to be working, is that the thermoswitch to relay connection is not direct. In an effort to save weight, parts count, etc. more and more computer modules are used for various functions. The fans could be turned on whenever the engine control module senses a particular temperature from the sender -- in which case a thermoswitch is not required. You'd need the car's wiring diagram to know this -- or call the dealer maybe... or ask at a parts store.

On most cars now, things that used to be really simple are fairly complex. Even interior lights are rarely turned on directly now, but are instead under control of the body computer. All these things are black boxes, from a diagnostic standpoint, but the actual electronics involved can be thousands of transistor junctions where there used to ba a wire and a switch. Personally, I'd rather have the interior lights in my Honda simply go off when I close the door, rather than having them slowly fade out after a delay -- but I'm an old fart.

Other thoughts:

With one of the relays removed, you could check the coil voltage at the engine temperature at which the fans should be running.

I wonder why there are separate relays for each fan? maybe they come on at different temperatures, in which case control by module would be likely.

Also make sure the thing you replaced was the actual thermoswitch, as opposed to the temperature sender (for the gauge).

As I'm writing this, I'm thinking you really need the wiring diagram for the car, if the obvious tests don't pinpoint the culprit.

If your are stuck and need to use the car, you can always replace a relay with a toggle switch wired to two short leads with terminals to match the relay. Turn the switch on when you are driving, off when you are not. (The fans are not shut off w/ the ignition if they share a fuse with the headlights.)

It sounds like you are pretty adept at this stuff -- but do beware of creating sparks around the battery (low probability of anything happening, but I keep remembering my wife trying to jump start our car: she wiggled the cable to improve the connection, and boom, the entire top of the battery blew off, followed by an acid shower.

Also, take all this advice with this caveat: I'm an old fart who used to twist wrenches professionally quite a while ago, but only work on my own cars now. My own cars have been very reliable, so I'm less in the loop than I used to be.

Watch the papers for reviews of my next novel.

If you used a jumper to cross the relay it proves the power supply to the fan is OK. it also proves the switching circuit is not working. The probably cause is the thermostat. To verify the thermostat is operational, remove the two wires and cross them, if the fan fires the stat is at fault. If there is only one wire on the stat, ground that wire.

remove stat and place in boiling water, check for continunity across poles.

One thing nobody has mentioned is the air-conditioner bypass. I am assuming your car is air-conditioned when I say this but in most vehicles whenever the air-conditioner compressor is running they have some sort of control that bypasses the temperature sensor and runs all the fans flat out. Normally you would expect this to cause the fans to run all the time but given the way auto designers love to make things as complex as possible anything could happen.

Since there are three separate relays it would tend to indicate that they were meant to com on sequentially as the temperature rises. For this to be possible there would need to be some sort of temperature sensor/transmitter rather than a simple temperature switch that closes at a particular temperature and a fault in this circuitry could cause the problem you are seeing.

All this is based on logical assumptions and if there is anything I have learnt over the years there is no logic involved in the electric/electronics in a car. You really need the wiring diagram and even then it can be an uphill battle. If you have a wiring diagram and access a scanner scan it in. post it here and we can see if it gives us an idea of what is going on.

CAUTION: Exposure to automotive wring/circuit diagrams may be hazardous to you health. Minor exposure is know to cause severe depression, confusion, and fits of uncontrollable laughter. Exposure should be kept to a minimum and prolonged exposure should be avoided.

CAUTION: Exposure to automotive wring/circuit diagrams may be hazardous to you health. Minor exposure is know to cause severe depression, confusion, and fits of uncontrollable laughter. Exposure should be kept to a minimum and prolonged exposure should be avoided.

Arrr Masu, I see that Oz has car electronics designed by that great German electrical designer, Professor Spitzensparken. I and my co-conspirators have spent many an unhappy hour rewiring factory looms to achieve power flow in some cars, and I thought this was some strange act of revenge on us Brits! Now I know that other countries are not exempt, I find life a little happier!

PS. My first thought is lack of coolant!

every car with an electric fan has a CCM constant control module. In many instances it looks like an otherwise superflouos black box inside of the engine compartment in most cases within 6-8" of the radiator. There in lies your problem. Trace the wiring harness back from the relay block or other locality known to you to end up at the radiator. Along the way you will trip across your culprit. With the inclination to to dismiss said black box as a mysterious bystander.You get past that and the air will be flowing like aunt Sally after lunch at Chipoltes.

The top of the engine has an air bleed vent to alow the heads and manifold to be filled with coolant after cooling system repairs.

since it was working until you broke the sensor i would suspect that the sensor is a bad one or a wrong one, most people try to compicate things when something like this happens so take that sensor to the local autozone and get another one and try it again.

I agree with pilotcraig2001 Many times I have bought new parts only to have them defective, especially if you buy them from a discount auto parts store

Temperature sensors could be bad or your thermostat.

Agreed, the new part may be bad, and it's a good sign if the fans run in A/C position. However, don't forget to 1) follow the trouble shooting guide in your manual (or ask to see one at Auto Zone, etc.) and 2) always recheck your work, especially if it worked before you worked on it. The troubleshooting list really helps eliminate each potential item in the order listed. (The best mechanics, NEVER guess what the problem is and then start replacing parts. They work their way through the manufacturer's check list. Works every time. Better than my buddy who years ago, replaced first the battery ($75), then the starter ($125) then noticed his grounding strap was bad ($6.00!).) Also, your manual should point out where everything is located so you're without excuse there. Finally, don't forget to try electrical contact cleaner on module contacts. Just worked on my brother's '90 Taurus wagon, the fan would run on the A/C position, other wise overheated. Finally, contact cleaner solved the problem, but the illustrated parts list, trouble shooting guide and patience all really helped solve this preplexing problem. Good luck!

I think your advice is very good, although I do not place as much faith in the manual troubleshooting charts as you do. I've found some factory and after market manuals to be both incomplete and inconsistent re troubleshooting. (Some manuals are excellent; some are pretty poor).

The rest of this is a rant, not aimed at anything you've said:

Many manuals suggest replacing components without first testing them, using a reasonably logical process of elimination. If the manual provides temperature vs resistance data for a sensor, then you can verify that the sensor is, in fact, bad before making the trip to the auto parts store (But most manuals do not: in a dealership setting, is is quicker to just replace the component as a part of troubleshooting sequence). Also, manuals often fail to make your recommendation to clean terminals -- something which often occurs naturally in the process of disconnecting and reconnecting components. What happens all too often in shop settings, is that components get replaced (cleaning contacts by normal wiping action in the process) and because the problem is cured, the assumption is that the component actually had to be replaced. (In line with your starter story, I'd wager that nearly half the starters replaced end up "curing the problem" not because of the new starter, but because of removing and re-tightening the connections.)

These trouble shooting charts are often written with the assumption that the reader works in a dealership, where it is quicker and cheaper (in labor) to swap a component. The result is that when you pick up your car, they often tell you they've replaced a series of components, and logic tells you that only one probably failed.

Another problem with manuals is that they often treat expensive items as black boxes when they are not. For example, I pulled the starter on my 96 Plymouth Voyager, after having followed the logical troubleshooting path. This was a simple process not requiring a manual. Had I read the manual, the process would have ended "Replace starter." But I knew that based on the mileage, the starter probably only needed new brushes. These were unavailable at the dealership, where they told me "You have to replace the whole starter." So I called around and found a starter shop which would sell me the brushes for $5. It took about 5 minutes to evaluate the condition of the commutator, which had worn about .0005" (just enough to be measurable with a good mic -- i.e. not at all) and replace the brushes. Even if I were paying for the work, it would have been far cheaper than replacing the starter. The starter went on for another 100,000 miles -- and may still be working for the new owner.

Where this sort of thing reaches logical absurdity is with Porsche, where if any internal work is required on the engine, the dealer replaces the entire thing! Granted it has been a while since I've worked on Porshes, but when I did, they were very well-engineered and no more difficult to work on that any other car. (Even more tangential to the original discussion: when I was working on Porsches, which I LOVE, engines in cars like Honda were already much more accurately machined. Posches required a lot of hand fitting (matching particular piston sizes with particular cylinder sizes, etc.) that was not required in Hondas. In fact, going back even further, I worked on both Honda and BMW motorcycles. Again, the Hondas were more precise, with the only selective fitting required being for main bearing journals -- which you did by matching bearings to marks already stamped on the connecting rod and rod journal. You'd have a very hard time getting the fit as precise by using ordinary shop mics. Honda gearboxes went together without any need for shimming, whereas the BMW gearboxes had to be shimmed -- and too many had to be reshimmed as brand new bikes.)

WOW, yet another novel. I'm not only an old fart, but a curmudgeon as well!

Having just finished a rebuild on a Honda engine, I couldn't agree more!

Many interesting points have been made. I use online forums a lot to solve my own problems. Because every specific vehicle model is prone to its "typical" set of problems, online you can find the likely root of failure. I think your issue is different.

I'm going to go on a limb and guess your thermostat isn't opening and is either sticking or it's installed upside down. It would be safe to replace it regardless after overheating.

no metal is a better conductor of heat than water, even with no water the sensor would actuate upon overheating fault is electrical

the car nuts at camaroz28.com could help you i think. one of the best tech forums for that model car