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Username Post: main firewall plug 62 impala        (Topic#373778)
Posts: 46

Loc: sf bay area
Reg: 12-08-22
09-18-23 08:44 AM - Post#2862638    

so it looks like my firewall plug is loose or going bad. i pulled into the gas station and it flat out died, no power no crank no nothing. i gently pushed the plug inwards from the engine bay side to regain any lost contact that might have occurred and that worked (thank god). now aside from changing out the whole wiring which iirc is going to be about 4-5k labor, can i do something temporarily to fix this problem like JUST upgrade the harness at the firewall to a new one? would you all consider just doing that if its possible... thanks fo any input

62 Impala Rag
92 5.0 Coupe


Silver Supporting Member
Posts: 254
Age: 68
Loc: Charlotte, NC, USA
Reg: 09-05-22
09-18-23 10:07 AM - Post#2862642    
    In response to fredfifty

That firewall junction is a common place for corrosion, so try cleaning it up as best you can and see if that fixes it. If not, you can certainly just replace the under-hood portion first (easiest) and see what you get.

'65 Impala SS 396 Convertible

Frequent Contributor
Posts: 2364
Loc: Orange CA
Reg: 11-07-03
09-18-23 05:24 PM - Post#2862651    
    In response to fredfifty

You could try come contact cleaner, like DeOxit on the connector. On my 64, the main (thick) wire was the real problem. Heating from too much draw on the circuits caused heating of the contact spring, causing it to not press as hard, making poor contact and arcing, causing more heat and so on...
You can try prying the spring side out to regain some of the pressure and cleaning things up and hope it will make better contact for a time. Ultimately replacing it is needed and what I did. I had hacked up my wiring harness with stereo installs back in the 80's, so replacement was needed anyways.

- Dave
1964 Impala 4-door sedan

"11th Year" Gold Supporting Member
Posts: 3601
Loc: Sergeant Bluff, Iowa
Reg: 01-10-05
09-18-23 09:09 PM - Post#2862658    
    In response to fredfifty

There is no way there is $4000 to $5000 labor to replace the underdash wiring harness which has the fuse box that plugs to the starter harness and headlight / alternator harness.
These 3 factory wiring harnesses are available from American Autowire and these harnesses are easy to install ( if you can’t clean the fuse box and two underhood harness as suggested above).

57 BelairHT 283/270hp 4 spd
62 ImpHT 327/300 4 spd
62 Imp CV SS 327/300HP 700R4 (sold)
62 Imp HT SS 409/482 stroker 4 spd
62 Imp SS 409 - 5 spd Convertible

Frequent Contributor
Posts: 1748
Loc: Houston TX
Reg: 04-15-11
09-19-23 03:19 AM - Post#2862660    
    In response to pvs409

I agree with Paul, the headlight and engine harness are simple plug and play from AAW. Those two harness’ clips are the weak points and get worn out. Replace those two and you will be fine.

64 Impala SS:
Chevy Performance 350HO
4 Speed Muncie

Senior Member
Posts: 1334

Loc: Custar, Ohio United State...
Reg: 12-10-01
09-19-23 10:19 AM - Post#2862673    
    In response to kingkreeton

If you do replace the harness make sure you tape and label each wire as your remove the old ones and that will eliminate any guess work on reassembly.

"3rd Year" Gold Supporting Member
Posts: 361
Loc: upstate NY
Reg: 11-12-19
09-21-23 03:41 PM - Post#2862730    
    In response to Dave_Neiling

I'll do it for $2500....

'65 Impala SS, Crocus Yellow/blk
327 / 300 L74
M11 3 on the tree
12 bolt 3.31 open dif


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