Relay under hood getting VERY hot
10-24-2016, 03:02 PM
#1
Burning Brakes
Thread Starter
Relay under hood getting VERY hot
I have a relay under my hood that's getting VERY hot. So hot, it will blister your finger.
It's a silver rectangular relay, bolted to the fire wall on the drivers side. It has a part number stamped on top, 3990842. It has two plugs on the bottom. I have Goggled and searched, and as best I can tell, this is a Smog Reversing Relay...what ever that is.
A couple of questions:
Why would it be getting this hot?
What does this relay do?
It's a silver rectangular relay, bolted to the fire wall on the drivers side. It has a part number stamped on top, 3990842. It has two plugs on the bottom. I have Goggled and searched, and as best I can tell, this is a Smog Reversing Relay...what ever that is.
A couple of questions:
Why would it be getting this hot?
What does this relay do?
10-24-2016, 03:07 PM
#2
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Model year?
10-24-2016, 03:35 PM
#4
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Hi v,
Those 2 relays are part of the emission control system on 71 cars. It's called the Combined Emission Control system (CEC).
The system when functioning properly controls idle rpm and vacuum advance under certain operating conditions.
It consists of:
a solenoid mounted to the front left of the carb
a temperature sensor in the right side head between the rear 2 spark plugs
a switch in the transmission that senses when the transmission is in 3rd and 4th gear in 4-speed cars or 3rd and reverse in automatic equipped cars
a reversing relay on the firewall
a delay timer on the firewall.
To determine why the reversing relay is hot it would be good to know:
is this is a new problem, or one you just realized?
are the other system components in place?
do you know if the system has been operating?
For the time being I'd pull the electrical connector on the relay so the overheating does't start a fire.
Regards,
Alan
Those 2 relays are part of the emission control system on 71 cars. It's called the Combined Emission Control system (CEC).
The system when functioning properly controls idle rpm and vacuum advance under certain operating conditions.
It consists of:
a solenoid mounted to the front left of the carb
a temperature sensor in the right side head between the rear 2 spark plugs
a switch in the transmission that senses when the transmission is in 3rd and 4th gear in 4-speed cars or 3rd and reverse in automatic equipped cars
a reversing relay on the firewall
a delay timer on the firewall.
To determine why the reversing relay is hot it would be good to know:
is this is a new problem, or one you just realized?
are the other system components in place?
do you know if the system has been operating?
For the time being I'd pull the electrical connector on the relay so the overheating does't start a fire.
Regards,
Alan
Last edited by Alan 71; 10-24-2016 at 03:48 PM.
10-24-2016, 04:31 PM
#5
Burning Brakes
Thread Starter
Hi v,
Those 2 relays are part of the emission control system on 71 cars. It's called the Combined Emission Control system (CEC).
The system when functioning properly controls idle rpm and vacuum advance under certain operating conditions.
It consists of:
a solenoid mounted to the front left of the carb
a temperature sensor in the right side head between the rear 2 spark plugs
a switch in the transmission that senses when the transmission is in 3rd and 4th gear in 4-speed cars or 3rd and reverse in automatic equipped cars
a reversing relay on the firewall
a delay timer on the firewall.
To determine why the reversing relay is hot it would be good to know:
is this is a new problem, or one you just realized?
are the other system components in place?
do you know if the system has been operating?
For the time being I'd pull the electrical connector on the relay so the overheating does't start a fire.
Regards,
Alan
Those 2 relays are part of the emission control system on 71 cars. It's called the Combined Emission Control system (CEC).
The system when functioning properly controls idle rpm and vacuum advance under certain operating conditions.
It consists of:
a solenoid mounted to the front left of the carb
a temperature sensor in the right side head between the rear 2 spark plugs
a switch in the transmission that senses when the transmission is in 3rd and 4th gear in 4-speed cars or 3rd and reverse in automatic equipped cars
a reversing relay on the firewall
a delay timer on the firewall.
To determine why the reversing relay is hot it would be good to know:
is this is a new problem, or one you just realized?
are the other system components in place?
do you know if the system has been operating?
For the time being I'd pull the electrical connector on the relay so the overheating does't start a fire.
Regards,
Alan
I have never noticed it before now. Part of the components are still there and connected...but the temp sensor in the head is removed. So, I assume it doesn't work.
I've been chasing another electrical gremlins lately and I have been checking all the relays. This is the only one that seems to be getting this hot. I had unplugged it, but it didn't have any affect on my other problems.
10-24-2016, 05:26 PM
#7
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Hi V,
There were typically 2 relays there… the reversing relay and the delay timer.
Regards,
Alan
There were typically 2 relays there… the reversing relay and the delay timer.
Regards,
Alan
10-26-2016, 04:10 PM
#8
Burning Brakes
Thread Starter
Problem solved!!! OK...with the help of a local Corvette repair shop here in the B'ham area, they found my problem.
There was a bad wire going to the windshield wiper motor. It was "back feeding" power back to the fuse box, which in turn was supplying power to the radio, the wipers and the reversing relay and delay timer relay even when the ignition switch was off.
A couple of snips and some wiring and the problem is solved. Relays are not getting excessively hot any longer and everything is back to working correctly as original. Only cost me $45.00!!! Great deal to have my baby back correct again!!!
There was a bad wire going to the windshield wiper motor. It was "back feeding" power back to the fuse box, which in turn was supplying power to the radio, the wipers and the reversing relay and delay timer relay even when the ignition switch was off.
A couple of snips and some wiring and the problem is solved. Relays are not getting excessively hot any longer and everything is back to working correctly as original. Only cost me $45.00!!! Great deal to have my baby back correct again!!!
10-26-2016, 04:50 PM
#9
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Hi V,
Sounds like a good outcome to me!
Regards,
Alan
Puzzles me that the radio could be involved since that's on the dash harness but the other items are on the engine harness.
Perhaps the wiring to the wiper/washer switch ties the 2 harnesses together and thus the radio enters into the mix?!?
Sounds like a good outcome to me!
Regards,
Alan
Puzzles me that the radio could be involved since that's on the dash harness but the other items are on the engine harness.
Perhaps the wiring to the wiper/washer switch ties the 2 harnesses together and thus the radio enters into the mix?!?
10-26-2016, 05:13 PM
#10
Burning Brakes
Thread Starter
Hi V,
Sounds like a good outcome to me!
Regards,
Alan
Puzzles me that the radio could be involved since that's on the dash harness but the other items are on the engine harness.
Perhaps the wiring to the wiper/washer switch ties the 2 harnesses together and thus the radio enters into the mix?!?
Sounds like a good outcome to me!
Regards,
Alan
Puzzles me that the radio could be involved since that's on the dash harness but the other items are on the engine harness.
Perhaps the wiring to the wiper/washer switch ties the 2 harnesses together and thus the radio enters into the mix?!?