Engine Bay Relays...what do they do?

[tgittens]

So my 1969 didn't start this morning...no crank...nothing...all lights were working...radio...check. So I went into the engine looking around and found two relays in the fuse box III (i think it's called) that were completely corroded and rusted and figured it had something to do with my no start situation...but alas it was just a dead battery (Optima 6 months old BTW).

Now I'm wondering what those two relays are...any ideas? I pulled them and the car ran as usual. I figure one is the rear window defrost and the other is the start enrichment but why do I need the start enrichment if my car runs fine without it?

thanks

[Flieger]

Because it may not start so easily if the weather changes.

Also, your car may "run fine" but be tuned rich, as many MFI systems are to compensate for poor idle do to worn throttle bodies. Sometimes if start enrichment does not work correctly, a home mechanic may have tuned the MFI rich with the main rack to compensate, without finding the real cause of the poor starting- worn throttle bodies. This would mean that you have enough fuel at start up without enrichment but are too rich and loosing power up in the revs.

I took off the fuel squirter lines to the stacks on my 2.7 RS spec MFI engine thinking that sunny southern california weather would not require "cold-start enrichment". It became VERY hard to start- to the point of concern over starter wear and valvtrain weat from cranking like that. I hooked the lines back up and it started like a treat. My throttle bodies are "tired", for the record. They allow too much air past the shafts for proper low speed manners. Lots of reversion pops today because of the dryer, leaner weather.

Sorry for the ramblings, YMMV

[OptimaJim]

tgittens, I’m sorry to hear about your Optima and engine bay relays. I don’t know how long your car sits idle, but if it does sit for extended periods of time, a battery tender/maintainer will extend the life of any battery. Fully-charged RedTops should measure in the range of 12.6-12.8 volts. Voltage measurements of the battery when the engine is running are the output of your alternator and should be in the range of 13.7-14.7 volts.

If you don’t have a multimeter you can test this by starting the car and turning on the headlights. If they are dim, it indicates the lights are running off the battery and that little or no juice is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged. If the lights have normal brightness and don't change intensity as the engine is revved, your charging system is probably functioning normally. If this checks out okay, you should check whether or not the battery is holding a charge, or if something on the vehicle is discharging the battery.

A high parasitic draw ("key off" load) can quickly discharge a battery and decrease its service life. This may be caused by a GPS, alarm system, bad relays or any other electrical device. Current drain on the battery can be checked with an ammeter. With the ignition off, disconnect one of the battery cables. Connect one ammeter lead to the battery and the other to the cable. The normal current drain on most vehicles should be about 25 milliamps or less. If the key-off drain exceeds 100 milliamps, there's an electrical issue that requires further diagnosis. If you don’t want to take your car to a mechanic, the easiest way to isolate the problem is to pull one fuse at a time from the fuse panel until the ammeter reading drops.

There may also be a problem with your battery that is causing it to not hold a charge. To check this, wait 12-24 hours after charging to the full voltage, keeping the battery out of the vehicle and measuring its voltage (another faster but less preferable way to do this is to turn on the high beam headlights for 15 seconds, turn them off, wait 5-10 minutes, then check the voltage). If you measure the voltage of the battery the next day, week, or even a month later, the voltage should be close to the max voltages listed above. If the voltage holds when not installed in your vehicle but drops when it is in your vehicle, you may have an issue with a parasitic draw.

If your battery was somehow discharged and your charger is not able to properly charge your deeply discharged battery, you can follow this link for directions for charging a deeply discharged battery- http://optimabatteries.com/product_s...s.php#charging

I hope you are able to resolve your issue. If you have any questions regarding our batteries, I’ll do my best to answer them.

Jim McIlvaine
eCare Manager, OPTIMA Batteries, Inc.